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relational-record-examples-0.5.1.0: src/specializedExamples.hs

{-# LANGUAGE MonadComprehensions #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DataKinds #-}

import Database.Relational.Query.SQLite3

import GHC.Generics (Generic)
import Prelude hiding (product)
import Data.Int (Int64)
import Data.Time (Day, LocalTime)
import Data.Functor.ProductIsomorphic ((|$|), (|*|))

import qualified Account
import Account (Account, account)
import qualified Branch
import Branch (Branch, branch)
import qualified Business
import Business (business)
import qualified Customer
import Customer (Customer, customer)
import qualified Department
import Department (Department, department)
import qualified Individual
import Individual (individual)
--import qualified Officer
--import Officer (Officer, Officer)
import qualified Product
import Product (product)
--import qualified ProductType
--import ProductType (ProductType, productType)
import qualified Transaction
-- import Transaction (transaction)
import qualified Employee
import Employee (Employee, employee)

allAccount :: Relation () Account
allAccount = relation $ query account

-- | sql/3.7
--
-- Handwritten SQL:
--
-- @
--   SELECT open_emp_id, product_cd
--   FROM account
--   ORDER BY open_emp_id, product_cd
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.open_emp_id AS f0, T0.product_cd AS f1 FROM MAIN.account
--   T0 ORDER BY T0.open_emp_id ASC, T0.product_cd ASC
-- @
--
account_3_7 :: Relation () (Maybe Int, String)
account_3_7 = relation $ do
  a <- query account
  let proj = (,) |$| a ! Account.openEmpId'
                 |*| a ! Account.productCd'
  asc proj
  return proj

-- | sql/3.7.1
--
-- Handwritten SQL:
--
-- @
--   SELECT account_id, product_cd, open_date, avail_balance
--   FROM account
--   ORDER BY avail_balance DESC
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.open_date AS
--   f2, T0.avail_balance AS f3 FROM MAIN.account T0 ORDER BY
--   T0.avail_balance DESC
-- @
--
account_3_7_1 :: Relation () Account2
account_3_7_1 = relation $ do
  a <- query account
  desc $ a ! Account.availBalance'
  return $ Account2 |$| a ! Account.accountId'
                    |*| a ! Account.productCd'
                    |*| a ! Account.openDate'
                    |*| a ! Account.availBalance'

data Account2 = Account2
  { a2AccountId :: Int
  , a2ProductCd :: String
  , a2OpenDate :: Day
  , a2AvailBalance :: Maybe Double
  } deriving (Show, Generic)

$(makeRelationalRecord ''Account2)

-- | sql/3.7.3
--
-- For backwards compatibility with the SQL92 version of standard, you can
-- use numbers instead of names to specify the columns that should be sorted.
-- With HRR you cannot use numbers for such purpose.
--
-- Handwritten SQL:
--
-- @
--   SELECT emp_id, title, start_date, fname, lname
--   FROM employee
--   ORDER BY 2,5
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.title AS f1, T0.start_date AS f2,
--   T0.fname AS f3, T0.lname AS f4 FROM MAIN.employee T0 ORDER BY T0.title
--   ASC, T0.lname ASC
-- @
--
employee_3_7_3 :: Relation () Employee1
employee_3_7_3 = relation $ do
  e <- query employee
  asc $ e ! Employee.title'
  asc $ e ! Employee.lname'
  return $ Employee1 |$| e ! Employee.empId'
                     |*| e ! Employee.title'
                     |*| e ! Employee.startDate'
                     |*| e ! Employee.fname'
                     |*| e ! Employee.lname'

data Employee1 = Employee1
  { e1EmpId :: Int
  , e1Title :: Maybe String
  , e1StartDate :: Day
  , e1Fname :: String
  , e1Lname' :: String
  } deriving (Show, Generic)

$(makeRelationalRecord ''Employee1)

-- | sql/4.1.2
--
-- HRR supports date literal of the SQL standard, such like Date '2003-01-01'.
-- However, SQLite has its own date literal without Date keyword,
-- like this: '2003-01-01'. So, you have to define a function to support
-- SQLite's date literal. Here we define 'unsafeSQLiteDayValue' function
-- for that.
--
-- Handwritten SQL:
--
-- @
--   SELECT *
--   FROM employee
--   WHERE end_date IS NULL AND (title = 'Teller' OR start_date < '2003-01-01')
-- @
--
-- Literal version of Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3, T0.end_date AS f4, T0.superior_emp_id AS f5,
--   T0.dept_id AS f6, T0.title AS f7, T0.assigned_branch_id AS f8 FROM
--   MAIN.employee T0 WHERE ((T0.end_date IS NULL) AND ((T0.title
--   = 'Teller') OR (T0.start_date < '2003-01-01')))
-- @
--
employee_4_1_2 :: Relation () Employee
employee_4_1_2 = relation $ do
  e <- query employee
  wheres $ isNothing (e ! Employee.endDate')
  wheres $ e ! Employee.title' .=. just (value "Teller")
     `or'` e ! Employee.startDate' .<. unsafeSQLiteDayValue "2003-01-01"
  return e

unsafeSQLiteDayValue :: SqlContext c => String -> Record c Day
unsafeSQLiteDayValue = unsafeProjectSqlTerms . showConstantTermsSQL

-- |
-- Another way, use a placeholder instead of a date literal.
-- There is no need to define a helper function.
--
-- Placeholder version of Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3, T0.end_date AS f4, T0.superior_emp_id AS f5,
--   T0.dept_id AS f6, T0.title AS f7, T0.assigned_branch_id AS f8 FROM
--   MAIN.employee T0 WHERE ((T0.end_date IS NULL) AND ((T0.title
--   = 'Teller') OR (T0.start_date < ?)))
-- @
--
employee_4_1_2P :: Relation Day Employee
employee_4_1_2P = relation' . placeholder $ \ph -> do
  e <- query employee
  wheres $ isNothing (e ! Employee.endDate')
  wheres $ e ! Employee.title' .=. just (value "Teller")
     `or'` e ! Employee.startDate' .<. ph
  return e

-- | sql/4.3.2
--
-- Handwritten SQL:
--
-- @
--   SELECT emp_id, fname, lname, start_date FROM employee
--   WHERE start_date
--   BETWEEN date('2001-01-01') AND date('2002-12-31')
-- @
--
-- Literal version of Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3 FROM MAIN.employee T0 WHERE ((T0.start_date >=
--   '2001-01-01') AND (T0.start_date <= '2003-01-01'))
-- @
--
employee_4_3_2 :: Relation () Employee2
employee_4_3_2 = relation $ do
  e <- query employee
  wheres $ e ! Employee.startDate' .>=. unsafeSQLiteDayValue "2001-01-01"
  wheres $ e ! Employee.startDate' .<=. unsafeSQLiteDayValue "2003-01-01"
  return $ Employee2 |$| e ! Employee.empId'
                     |*| e ! Employee.fname'
                     |*| e ! Employee.lname'
                     |*| e ! Employee.startDate'

-- |
-- Placeholder version of Generated SQL:
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3 FROM MAIN.employee T0 WHERE ((T0.start_date >= ?)
--   AND (T0.start_date <= ?))
-- @
--
-- NOTE: Be careful on the order of the placeholders. You must give day
-- values in order that they appear on the generated SQL.
--
employee_4_3_2P :: Relation (Day,Day) Employee2
employee_4_3_2P = relation' . placeholder $ \ph -> do
  e <- query employee
  let date = e ! Employee.startDate'
  wheres $ date .>=. ph ! fst'
  wheres $ date .<=. ph ! snd'
  return $ Employee2 |$| e ! Employee.empId'
                     |*| e ! Employee.fname'
                     |*| e ! Employee.lname'
                     |*| date

data Employee2 = Employee2
  { e2EmpId :: Int
  , e2Fname :: String
  , e2Lname :: String
  , e2StartDate :: Day
  } deriving (Show, Generic)

$(makeRelationalRecord ''Employee2)

-- | sql/4.3.3a.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT account_id, product_cd, cust_id, avail_balance
--   FROM LEARNINGSQL.account
--   WHERE product_cd IN ('CHK', 'SAV', 'CD', 'MM')
-- @
--
-- record version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.open_date AS f3, T0.close_date AS f4, T0.last_activity_date AS f5,
--   T0.status AS f6, T0.open_branch_id AS f7, T0.open_emp_id AS f8,
--   T0.avail_balance AS f9, T0.pending_balance AS f10 FROM MAIN.account T0
--   WHERE (T0.product_cd IN ('CHK', 'SAV', 'CD', 'MM'))
-- @
--
account_4_3_3a :: Relation () Account
account_4_3_3a = relation $ do
  a  <- query account
  wheres $ a ! Account.productCd' `in'` values ["CHK", "SAV", "CD", "MM"]
  return a

-- |
-- tuple version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.avail_balance AS f3 FROM MAIN.account T0 WHERE (T0.product_cd IN
--   ('CHK', 'SAV', 'CD', 'MM'))
-- @
--
account_4_3_3aT :: Relation () (Int, String, Int, Maybe Double)
account_4_3_3aT = relation $ do
  a  <- query account
  wheres $ a ! Account.productCd' `in'` values ["CHK", "SAV", "CD", "MM"]
  return $ (,,,) |$| a ! Account.accountId' |*| a ! Account.productCd' |*| a ! Account.custId' |*| a ! Account.availBalance'

-- |
-- Adhoc defined record version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.avail_balance AS f3 FROM MAIN.account T0 WHERE (T0.product_cd IN
--   ('CHK', 'SAV', 'CD', 'MM'))
-- @
--
-- Above sql is the same to the tuple version.
--
account_4_3_3aR :: Relation () Account1
account_4_3_3aR = relation $ do
  a  <- query account
  wheres $ a ! Account.productCd' `in'` values ["CHK", "SAV", "CD", "MM"]
  return $ Account1 |$| a ! Account.accountId'
                    |*| a ! Account.productCd'
                    |*| a ! Account.custId'
                    |*| a ! Account.availBalance'

data Account1 = Account1
  { a1AccountId :: Int
  , a1ProductCd :: String
  , a1CustId :: Int
  , a1AvailBalance :: Maybe Double
  } deriving (Show, Generic)

$(makeRelationalRecord ''Account1)

-- |
-- 9.1 What is a subquery?
--
-- Handwritten SQL:
--
-- @
--   SELECT account_id, product_cd, cust_id, avail_balance
--   FROM account
--   WHERE account_id = (SELECT MAX(account_id)
--                       FROM account);
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.avail_balance AS f3 FROM MAIN.account T0 WHERE (T0.account_id
--   = (SELECT ALL MAX (T1.account_id) AS f0 FROM MAIN.account T1))
-- @
--
account_9_1 :: Relation () Account1
account_9_1 = relation $ do
  a  <- query account
  ma <- queryScalar $ aggregatedUnique account Account.accountId' max'
  wheres $ just (a ! Account.accountId') .=. flattenMaybe ma
  return $ Account1 |$| a ! Account.accountId'
                    |*| a ! Account.productCd'
                    |*| a ! Account.custId'
                    |*| a ! Account.availBalance'

-- | sql/4.3.3b.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT account_id, product_cd, cust_id, avail_balance
--   FROM account
--   WHERE product_cd IN (SELECT product_cd FROM product
--   WHERE product_type_cd = 'ACCOUNT')
-- @
--
-- Record version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.open_date AS f3, T0.close_date AS f4, T0.last_activity_date AS f5,
--   T0.status AS f6, T0.open_branch_id AS f7, T0.open_emp_id AS f8,
--   T0.avail_balance AS f9, T0.pending_balance AS f10 FROM MAIN.account T0
--   WHERE (T0.product_cd IN (SELECT ALL T1.product_cd AS f0 FROM
--   MAIN.product T1 WHERE (T1.product_type_cd = ?)))
-- @
--
account_4_3_3b :: Relation String Account
account_4_3_3b = relation' $ do
  a <- query account
  (phProductCd,p) <- queryList' product_4_3_3b
  wheres $ a ! Account.productCd' `in'` p
  return (phProductCd, a)

-- |
-- Tuple version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.avail_balance AS f3 FROM MAIN.account T0 WHERE (T0.product_cd IN
--   (SELECT ALL T1.product_cd AS f0 FROM MAIN.product T1 WHERE
--   (T1.product_type_cd = ?)))
-- @
--
account_4_3_3bT :: Relation String (Int, String, Int, Maybe Double)
account_4_3_3bT = relation' $ do
  a <- query account
  (phProductCd,p) <- queryList' product_4_3_3b
  wheres $ a ! Account.productCd' `in'` p
  let at = (,,,) |$| a ! Account.accountId' |*| a ! Account.productCd' |*| a ! Account.custId' |*| a ! Account.availBalance'
  return (phProductCd, at)

-- |
-- Adhoc record version of Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.avail_balance AS f3 FROM MAIN.account T0 WHERE (T0.product_cd IN
--   (SELECT ALL T1.product_cd AS f0 FROM MAIN.product T1 WHERE
--   (T1.product_type_cd = ?)))
-- @
--
account_4_3_3bR :: Relation String Account1
account_4_3_3bR = relation' $ do
  a <- query account
  (phProductCd,p) <- queryList' product_4_3_3b
  wheres $ a ! Account.productCd' `in'` p
  let ar = Account1 |$| a ! Account.accountId'
                    |*| a ! Account.productCd'
                    |*| a ! Account.custId'
                    |*| a ! Account.availBalance'
  return (phProductCd, ar)

product_4_3_3b :: Relation String String
product_4_3_3b = relation' . placeholder $ \ph -> do
  p <- query product
  wheres $ p ! Product.productTypeCd' .=. ph
  return $ p ! Product.productCd'

-- | sql/4.3.3c.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT account_id, product_cd, cust_id, avail_balance
--   FROM LEARNINGSQL.account
--   WHERE product_cd NOT IN ('CHK', 'SAV', 'CD', 'MM')
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.product_cd AS f1, T0.cust_id AS f2,
--   T0.open_date AS f3, T0.close_date AS f4, T0.last_activity_date AS f5,
--   T0.status AS f6, T0.open_branch_id AS f7, T0.open_emp_id AS f8,
--   T0.avail_balance AS f9, T0.pending_balance AS f10 FROM MAIN.account T0
--   WHERE (NOT (T0.product_cd IN ('CHK', 'SAV', 'CD', 'MM')))
-- @
--
account_4_3_3c :: Relation () Account
account_4_3_3c = relation $ do
  a  <- query account
  wheres $ not' (a ! Account.productCd' `in'` values ["CHK", "SAV", "CD", "MM"])
  return a

-- | sql/5.1.2a.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT e.fname, e.lname, d.name
--   FROM LEARNINGSQL.employee e INNER JOIN LEARNINGSQL.department d
--   USING (dept_id)
-- @
--
-- Record version of Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3, T0.end_date AS f4, T0.superior_emp_id AS f5,
--   T0.dept_id AS f6, T0.title AS f7, T0.assigned_branch_id AS f8,
--   T1.dept_id AS f9, T1.name AS f10 FROM MAIN.employee T0 INNER JOIN
--   MAIN.department T1 ON (T0.dept_id = T1.dept_id)
-- @
--
join_5_1_2a :: Relation () (Employee, Department)
join_5_1_2a = relation $ do
  e  <- query employee
  d  <- query department
  on $ e ! Employee.deptId' .=. just (d ! Department.deptId')
  return $ e >< d

-- |
-- Tuple version of Generated SQL:
--
-- @
--   SELECT ALL T0.fname AS f0, T0.lname AS f1, T1.name AS f2 FROM
--   MAIN.employee T0 INNER JOIN MAIN.department T1 ON (T0.dept_id
--   = T1.dept_id)
-- @
--
join_5_1_2aT :: Relation () (String, String, String)
join_5_1_2aT = relation $ do
  e  <- query employee
  d  <- query department
  on $ e ! Employee.deptId' .=. just (d ! Department.deptId')
  return $ (,,) |$| e ! Employee.fname' |*| e ! Employee.lname' |*| d ! Department.name'

-- |
-- Left Outer Join
--
-- Handwritten SQL:
--
-- @
--  SELECT a.account_id, a.cust_id, i.fname, i.lname
--    FROM account a LEFT OUTER JOIN individual i
--      ON a.cust_id = i.cust_id
-- @
--
-- Generated SQL:
-- @
--   SELECT ALL T0.account_id AS f0, T0.cust_id AS f1, T1.fname AS f2,
--   T1.lname AS f3 FROM MAIN.account T0 LEFT JOIN MAIN.individual T1 ON
--   (T0.cust_id = T1.cust_id)
-- @
--
account_LeftOuterJoin :: Relation () Account4
account_LeftOuterJoin = relation $ do
  a <- query account
  i <- queryMaybe individual
  on $ just (a ! Account.custId') .=. i ?! Individual.custId'
  return $ Account4 |$| a ! Account.accountId'
                    |*| a ! Account.custId'
                    |*| i ?! Individual.fname'
                    |*| i ?! Individual.lname'

data Account4 = Account4
  { a4AccountId :: Int
  , a4CustId :: Int
  , a4Fname :: Maybe String
  , a4Lname :: Maybe String
  } deriving (Show, Generic)

$(makeRelationalRecord ''Account4)

-- |
-- Right Outer Join
--
-- Handwritten SQL:
--
-- @
-- SELECT c.cust_id, b.name
--   FROM customer c RIGHT OUTER JOIN business b
--       ON c.cust_id = b.cust_id
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.cust_id AS f0, T1.name AS f1 FROM MAIN.customer T0 RIGHT
--   JOIN MAIN.business T1 ON (T0.cust_id = T1.cust_id)
-- @
--
-- Note: A function using right-out-join can be defined, but unfortunately
-- SQLite3 does not support it.
--
business_RightOuterJoin :: Relation () (Maybe Int, String)
business_RightOuterJoin = relation $ do
  c <- queryMaybe customer
  b <- query business
  on $ c ?! Customer.custId' .=. just (b ! Business.custId')
  return (c ?! Customer.custId' >< b ! Business.name')

-- | sql/5.1.3.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT a.account_id, a.cust_id, a.open_date, a.product_cd
--   FROM account a INNER JOIN employee e ON a.open_emp_id = e.emp_id
--   INNER JOIN branch b ON e.assigned_branch_id = b.branch_id
--   WHERE e.start_date <= date('2004-01-01') AND
--        (e.title = 'Teller' OR e.title = 'Head Teller') AND
--             b.name = 'Woburn Branch'
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.account_id AS f0, T0.cust_id AS f1, T0.open_date AS f2,
--   T0.product_cd AS f3 FROM (MAIN.account T0 INNER JOIN MAIN.employee T1
--   ON (T0.open_emp_id = T1.emp_id)) INNER JOIN MAIN.branch T2 ON
--   (T1.assigned_branch_id = T2.branch_id) WHERE ((T1.start_date <=
--   '2004-01-01') AND (((T1.title = 'Teller') OR (T1.title = 'Head
--   Teller')) AND (T2.name = 'Woburn Branch')))
-- @
--
join_5_1_3 :: Relation () Account3
join_5_1_3 = relation $ do
  a <- query account
  e <- query employee
  on $ a ! Account.openEmpId' .=. just (e ! Employee.empId')

  b <- query branch
  on $ e ! Employee.assignedBranchId' .=. just (b ! Branch.branchId')

  wheres $ e ! Employee.startDate' .<=. unsafeSQLiteDayValue "2004-01-01"
  wheres $ e ! Employee.title' .=. just (value "Teller")
     `or'` e ! Employee.title' .=. just (value "Head Teller")
  wheres $ b ! Branch.name' .=. value "Woburn Branch"

  return $ Account3 |$| a ! Account.accountId'
                    |*| a ! Account.custId'
                    |*| a ! Account.openDate'
                    |*| a ! Account.productCd'

data Account3 = Account3
  { a3AccountId :: Int
  , a3CustId :: Int
  , a3OpenDate :: Day
  , a3ProductCd :: String
  } deriving (Show, Generic)

$(makeRelationalRecord ''Account3)

-- | sql/5.3a.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT e.fname, e.lname, e_mgr.fname mgr_fname, e_mgr.lname mgr_lname
--   FROM LEARNINGSQL.employee e INNER JOIN LEARNINGSQL.employee e_mgr
--   ON e.superior_emp_id = e_mgr.emp_id
-- @
--
-- Record version of Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.fname AS f1, T0.lname AS f2,
--   T0.start_date AS f3, T0.end_date AS f4, T0.superior_emp_id AS f5,
--   T0.dept_id AS f6, T0.title AS f7, T0.assigned_branch_id AS f8,
--   T1.emp_id AS f9, T1.fname AS f10, T1.lname AS f11, T1.start_date AS
--   f12, T1.end_date AS f13, T1.superior_emp_id AS f14, T1.dept_id AS f15,
--   T1.title AS f16, T1.assigned_branch_id AS f17 FROM MAIN.employee T0
--   INNER JOIN MAIN.employee T1 ON (T0.superior_emp_id = T1.emp_id)
-- @
--
selfJoin_5_3a :: Relation () (Employee, Employee)
selfJoin_5_3a = relation $ do
  e  <- query employee
  m  <- query employee
  on $ e ! Employee.superiorEmpId' .=. just (m ! Employee.empId')
  return $ e >< m

-- |
-- Tuple version of Generated SQL:
--
-- @
--   SELECT ALL T0.fname AS f0, T0.lname AS f1, T1.fname AS f2, T1.lname AS
--   f3 FROM MAIN.employee T0 INNER JOIN MAIN.employee T1 ON
--   (T0.superior_emp_id = T1.emp_id)
-- @
--
selfJoin_5_3aT :: Relation () ((String, String), (String, String))
selfJoin_5_3aT = relation $ do
  e  <- query employee
  m  <- query employee
  on $ e ! Employee.superiorEmpId' .=. just (m ! Employee.empId')
  let emp = e ! Employee.fname' >< e ! Employee.lname'
  let mgr = m ! Employee.fname' >< m ! Employee.lname'
  return $ emp >< mgr

-- | sql/6.4.1a.sh
--
-- The standard SQL allows the syntax of UNION that has an order clause
-- at the last of query. Unfortunately, HRR dows not support. In addition,
-- HRR put a select statement having an order clause into parentheses.
-- If you want to sort whole row returned from UNION, place a order
-- clouse outside of the union relation.
--
-- Handwritten SQL:
--
-- @
--   SELECT emp_id, assigned_branch_id
--   FROM LEARNINGSQL.employee
--   WHERE title = 'Teller'
--   UNION
--   SELECT open_emp_id, open_branch_id
--   FROM LEARNINGSQL.account
--   WHERE product_cd = 'SAV'
--   ORDER BY open_emp_id
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T2.f0 AS f0, T2.f1 AS f1 FROM (SELECT ALL T0.emp_id AS f0,
--   T0.assigned_branch_id AS f1 FROM MAIN.employee T0 WHERE (T0.title
--   = 'Teller') UNION SELECT ALL T1.open_emp_id AS f0, T1.open_branch_id
--   AS f1 FROM MAIN.account T1 WHERE (T1.product_cd = 'SAV')) T2 ORDER BY
--   T2.f0 ASC
-- @
--
employee_6_4_1a :: Relation () (Maybe Int, Maybe Int)
employee_6_4_1a = relation $ do
  e  <- query employee
  wheres $ e ! Employee.title' .=. just (value "Teller")
  return $ just (e ! Employee.empId') >< e ! Employee.assignedBranchId'

account_6_4_1a :: Relation () (Maybe Int, Maybe Int)
account_6_4_1a = relation $ do
  a  <- query account
  wheres $ a ! Account.productCd' .=. value "SAV"
  return $ a ! Account.openEmpId' >< a ! Account.openBranchId'

union_6_4_1a_Nest :: Relation () (Maybe Int, Maybe Int)
union_6_4_1a_Nest = relation $ do
  ea <- query $ employee_6_4_1a `union` account_6_4_1a
  asc $ ea ! fst'
  return ea

-- |
-- Generated SQL has different meaning with the handwritten SQL
-- (order clause with UNION).
-- Such query cannot be expressed flatly with EDSL of HRR.
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.emp_id AS f0, T0.assigned_branch_id AS f1 FROM
--   MAIN.employee T0 WHERE (T0.title = 'Teller') UNION SELECT ALL
--   T1.open_emp_id AS f0, T1.open_branch_id AS f1 FROM MAIN.account T1
--   WHERE (T1.product_cd = 'SAV')
-- @
--
union_6_4_1a_Flat :: Relation () (Maybe Int, Maybe Int)
union_6_4_1a_Flat = relation (do
    e  <- query employee
    wheres $ e ! Employee.title' .=. just (value "Teller")
    return $ just (e ! Employee.empId') >< e ! Employee.assignedBranchId'
  ) `union` relation (do
    a  <- query account
    wheres $ a ! Account.productCd' .=. value "SAV"
    -- asc $ a ! Account.openEmpId'
    return $ a ! Account.openEmpId' >< a ! Account.openBranchId'
  )

-- | sql/8.1a.sh
--
-- Handwritten SQL:
--
-- @
--   SELECT open_emp_id, COUNT(*) how_many
--   FROM LEARNINGSQL.account
--   GROUP BY open_emp_id
--   ORDER BY open_emp_id
-- @
--
-- Generated SQL:
--
-- @
--  SELECT ALL T0.open_emp_id AS f0, COUNT (T0.account_id) AS f1 FROM
--  MAIN.account T0 GROUP BY T0.open_emp_id ORDER BY T0.open_emp_id ASC
-- @
--
group_8_1a :: Relation () (Maybe Int, Int64)
group_8_1a = aggregateRelation $ do
  a  <- query account
  g  <- groupBy $ a ! Account.openEmpId'
  asc $ g ! id'
  return $ g >< count (a ! Account.accountId')

-- |
-- 9.4 Correlated Subqueries
--
-- Handwritten SQL:
--
-- @
--   SELECT c.cust_id, c.cust_type_cd, c.city
--   FROM customer c
--   WHERE 2 = (SELECT COUNT(*)
--              FROM account a
--              WHERE a.cust_id = c.cust_id);
-- @
--
-- Generated SQL:
--
-- @
--   SELECT ALL T0.cust_id AS f0, T0.cust_type_cd AS f1, T0.city AS f2 FROM
--   MAIN.customer T0 WHERE (2 = (SELECT ALL COUNT (T2.f0) AS f0 FROM
--   (SELECT ALL T1.account_id AS f0 FROM MAIN.account T1 WHERE (T1.cust_id
--   = T0.cust_id)) T2))
-- @
--
customer_9_4 :: Relation () Customer1
customer_9_4 = relation $ do
  c  <- query customer
  ca <- queryScalar $ aggregatedUnique (relation $ do
    a <- query account
    wheres $ a ! Account.custId' .=. c ! Customer.custId'
    return (a ! Account.accountId')
    ) id' count
  wheres $ just (value (2 :: Int64)) .=. ca
  return (customer1 c)

data Customer1 = Customer1
  { c1Custid :: Int
  , c1CustTypeCd :: String
  , c1City :: Maybe String
  } deriving (Show, Generic)

customer1 :: SqlContext c
          => Record c Customer -> Record c Customer1
customer1 c = Customer1 |$| c ! Customer.custId'
                        |*| c ! Customer.custTypeCd'
                        |*| c ! Customer.city'

$(makeRelationalRecord ''Customer1)

-- |
-- (from script) The insert statement
--
-- Handwritten SQL:
--
-- @
--   INSERT INTO branch (branch_id, name, address, city, state, zip)
--   VALUES (null, 'Headquarters', '3882 Main St.', 'Waltham', 'MA', '02451');
-- @
--
-- Literal version of Generated SQL:
--
-- @
--  INSERT INTO MAIN.branch (name, address, city, state, zip)
--  VALUES ('Headquarters', '3882 Main St.', 'Waltham', 'MA', '02451')
-- @
--
insertBranch_s1 :: Insert ()
insertBranch_s1 = insertValueNoPH $ do
  Branch.name'     <-#  value "Headquarters"
  Branch.address'  <-#  value (Just "3882 Main St.")
  Branch.city'     <-#  value (Just "Waltham")
  Branch.state'    <-#  value (Just "MA")
  Branch.zip'      <-#  value (Just "02451")

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   INSERT INTO MAIN.branch (name, address, city, state, zip)
--   VALUES (?, ?, ?, ?, ?)
-- @
--
insertBranch_s1P :: Insert Branch1
insertBranch_s1P = insert piBranch1

piBranch1 :: Pi Branch Branch1
piBranch1 = Branch1 |$| Branch.name'
                    |*| Branch.address'
                    |*| Branch.city'
                    |*| Branch.state'
                    |*| Branch.zip'

data Branch1 = Branch1
  { b1Name :: String
  , b1Address :: Maybe String
  , b1City :: Maybe String
  , b1State :: Maybe String
  , b1Zip :: Maybe String
  } deriving (Generic)

$(makeRelationalRecord ''Branch1)

branch1 :: Branch1
branch1 = Branch1
  { b1Name = "Headquarters"
  , b1Address = Just "3882 Main St."
  , b1City = Just "Waltham"
  , b1State = Just "MA"
  , b1Zip = Just "02451"
  }

-- |
-- Literal version of Generated SQL:
--
-- @
--  INSERT INTO MAIN.branch (name, address, city, state, zip)
--  VALUES ('Headquarters', '3882 Main St.', 'Waltham', 'MA', '02451')
-- @
--
-- Thanks to generic-programing, it is possible to specify record value directly as SQL row value.
-- Above SQL is the same to the monadic building version.
--
insertBranch_s1R :: Insert ()
insertBranch_s1R = insertValueNoPH $ do
  piBranch1   <-#  value Branch1
                         { b1Name = "Headquarters"
                         , b1Address = Just "3882 Main St."
                         , b1City = Just "Waltham"
                         , b1State = Just "MA"
                         , b1Zip = Just "02451"
                         }

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   INSERT INTO MAIN.branch (name, address, city, state, zip)
--   VALUES (?, ?, ?, ?, ?)
-- @
--
-- Thanks to generic-programing, it is possible to specify tuple type as Pi destination type.
-- Above SQL is the same to ad-hoc defined record version.
--
insertBranch_s1PT :: Insert (String, Maybe String, Maybe String, Maybe String, Maybe String)
insertBranch_s1PT = insert piBranchTuple

piBranchTuple :: Pi Branch (String, Maybe String, Maybe String, Maybe String, Maybe String)
piBranchTuple = (,,,,)
                |$| Branch.name'
                |*| Branch.address'
                |*| Branch.city'
                |*| Branch.state'
                |*| Branch.zip'

branchTuple :: (String, Maybe String, Maybe String, Maybe String, Maybe String)
branchTuple = ("Headquarters",
              Just "3882 Main St.",
              Just "Waltham",
              Just "MA",
              Just "02451")


-- |
-- (from script) The insert statement
--
-- Handwritten SQL:
--
-- @
--   INSERT INTO employee (emp_id, fname, lname, start_date,
--     dept_id, title, assigned_branch_id)
--   VALUES (null, 'Michael', 'Smith', '2001-06-22',
--     (SELECT dept_id FROM department WHERE name = 'Administration'),
--     'President',
--     (SELECT branch_id FROM branch WHERE name = 'Headquarters'));
-- @
--
-- Literal version of Generated SQL:
--
-- @
--   INSERT INTO MAIN.employee (fname, lname, start_date, dept_id, title,
--   assigned_branch_id) SELECT ALL 'Michael' AS f0, 'Smith' AS f1,
--   '2001-06-22' AS f2, T0.dept_id AS f3, 'President' AS f4, T1.branch_id
--   AS f5 FROM MAIN.department T0 INNER JOIN MAIN.branch T1 ON (0=0) WHERE
--   ((T0.name = 'Administration') AND (T1.name = 'Headquarters'))
-- @
--
-- Note: Since the name column of department table is not set with
-- an unique constraint, it is not possible to use queryScalar.
-- The name column of branch table is the same.
--
insertEmployee_s2 :: InsertQuery ()
insertEmployee_s2 = insertQuery piEmployee3 . relation $ do
  d <- query department
  b <- query branch
  wheres $ d ! Department.name' .=. value "Administration"
  wheres $ b ! Branch.name' .=. value "Headquarters"
  return $ Employee3 |$| value "Michael"
                     |*| value "Smith"
                     |*| unsafeSQLiteDayValue "2001-06-22"
                     |*| just (d ! Department.deptId')
                     |*| value (Just "President")
                     |*| just (b ! Branch.branchId')

-- this is equal to `defineDirectPi [1,2,3,6,7,8]'
piEmployee3 :: Pi Employee Employee3
piEmployee3 = Employee3 |$| Employee.fname'
                        |*| Employee.lname'
                        |*| Employee.startDate'
                        |*| Employee.deptId'
                        |*| Employee.title'
                        |*| Employee.assignedBranchId'

data Employee3 = Employee3
  { e3Fname :: String
  , e3Lname :: String
  , e3StartDate :: Day
  , e3DeptId :: Maybe Int
  , e3Title :: Maybe String
  , e3AssignedBranchId :: Maybe Int
  } deriving (Generic)

$(makeRelationalRecord ''Employee3)

-- |
-- In the following code we simulate to use queryScalar with using
-- unsafeUnique. By that means we throw away the safety given by HRR
-- and the type system.
--
-- Unsafe version of Generated SQL:
--
-- @
--   INSERT INTO MAIN.employee (fname, lname, start_date, dept_id, title,
--   assigned_branch_id) SELECT ALL 'Michael' AS f0, 'Smith' AS f1,
--   '2001-06-22' AS f2, (SELECT ALL T0.dept_id AS f0 FROM MAIN.department
--   T0 WHERE (T0.name = 'Administration')) AS f3, 'President' AS f4,
--   (SELECT ALL T1.branch_id AS f0 FROM MAIN.branch T1 WHERE (T1.name
--   = 'Headquarters')) AS f5
-- @
--
insertEmployee_s2U :: InsertQuery ()
insertEmployee_s2U = insertQuery piEmployee3 . relation $ do
  d <- queryScalar . unsafeUnique . relation $ do
    d' <- query department
    wheres $ d' ! Department.name' .=. value "Administration"
    return $ d' ! Department.deptId'
  b <- queryScalar . unsafeUnique . relation $ do
    b' <- query branch
    wheres $ b' ! Branch.name' .=. value "Headquarters"
    return $ b' ! Branch.branchId'
  return $ Employee3 |$| value "Michael"
                     |*| value "Smith"
                     |*| unsafeSQLiteDayValue "2001-06-22"
                     |*| d
                     |*| value (Just "President")
                     |*| b

-- place the definition of Employee4 that contains template-haskell, before
-- insertEmployee_s2P uses the function to be generated.
data Employee4 = Employee4
  { e4Fname :: String
  , e4Lname :: String
  , e4StartDate :: Day
  , e4Title :: Maybe String
  } deriving (Generic)

$(makeRelationalRecord ''Employee4)

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   INSERT INTO MAIN.employee (fname, lname, start_date, dept_id, title,
--   assigned_branch_id) SELECT ALL ? AS f0, ? AS f1, ? AS f2, T0.dept_id
--   AS f3, ? AS f4, T1.branch_id AS f5 FROM MAIN.department T0 INNER JOIN
--   MAIN.branch T1 ON (0=0) WHERE ((T0.name = 'Administration') AND
--   (T1.name = 'Headquarters'))
-- @
--
insertEmployee_s2P :: InsertQuery Employee4
insertEmployee_s2P = insertQuery piEmployee3 . relation' $ do
  d <- query department
  b <- query branch
  wheres $ d ! Department.name' .=. value "Administration"
  wheres $ b ! Branch.name' .=. value "Headquarters"
  placeholder $ \ph ->
    return $ Employee3 |$| ph ! e4Fname'
                       |*| ph ! e4Lname'
                       |*| ph ! e4StartDate'
                       |*| just (d ! Department.deptId')
                       |*| ph ! e4Title'
                       |*| just (b ! Branch.branchId')

employee4 :: Employee4
employee4 = Employee4
  { e4Fname = "Michael"
  , e4Lname = "Smith"
  , e4StartDate = read "2001-06-22"
  , e4Title = Just "President"
  }

-- |
-- (original) Updating data
--
-- Handwritten SQL:
--
-- @
--   UPDATE employee
--   SET lname = 'Bush',
--        dept_id = 3
--   WHERE emp_id = 10;
-- @
--
-- Generated SQL:
--
-- @
--   UPDATE MAIN.employee SET lname = 'Bush', dept_id = 3 WHERE (emp_id
--   = 10)
-- @
--
updateEmployee_o3 :: Update ()
updateEmployee_o3 = updateNoPH $ \proj -> do
  Employee.lname' <-# value "Bush"
  Employee.deptId' <-# just (value 3)
  wheres $ proj ! Employee.empId' .=. value 10

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   UPDATE MAIN.employee SET lname = ?, dept_id = ? WHERE (emp_id = ?)
-- @
--
-- Note: This function is equal to the following:
--
-- @
--   updateEmployee_o3P :: Update (String, Int, Int)
--   updateEmployee_o3P = derivedUpdate $ \proj -> do
--     (phLname,()) <- placeholder (\ph -> Employee.lname' <-# ph)
--     (phDeptId,()) <- placeholder (\ph -> Employee.deptId' <-# just ph)
--     (phEmpId,()) <- placeholder (\ph -> wheres $ proj ! Employee.empId' .=. ph)
--     return $ (,,) |$| phLname |*| phDeptId |*| phEmpId
-- @
--
updateEmployee_o3P :: Update (String, Int, Int)
updateEmployee_o3P = update $ \proj -> do
  (phLname,()) <- placeholder (\ph -> Employee.lname' <-# ph)
  (phDeptId,()) <- placeholder (\ph -> Employee.deptId' <-# just ph)
  (phEmpId,()) <- placeholder (\ph -> wheres $ proj ! Employee.empId' .=. ph)
  return $ (,,) |$| phLname |*| phDeptId |*| phEmpId

-- |
-- 9.4.2 Data Manipulation Using Correlated Subqueries
--
-- Handwritten SQL:
--
-- @
--   UPDATE account
--   SET last_activity_date =
--      (SELECT MAX(t.txn_date)
--       FROM transaction0 t
--       WHERE t.account_id = account.account_id)
--   WHERE EXISTS (SELECT 1
--                 FROM transaction0 t
--                 WHERE t.account_id = account.account_id);
-- @
--
-- Generated SQL:
--
-- @
--   UPDATE MAIN.account SET last_activity_date = date((SELECT ALL MAX
--   (T1.f0) AS f0 FROM (SELECT ALL T0.txn_date AS f0 FROM
--   MAIN.transaction0 T0 WHERE (T0.account_id = account_id)) T1)) WHERE
--   (EXISTS (SELECT ALL 1 AS f0 FROM MAIN.transaction0 T2 WHERE
--   (T2.account_id = account_id)))
-- @
--
updateAccount_9_4_2 :: Update ()
updateAccount_9_4_2 = updateNoPH $ \proj -> do
  ts <- queryScalar $ aggregatedUnique (relation $ do
    t <- query Transaction.transaction
    wheres $ t ! Transaction.accountId' .=. proj ! Account.accountId'
    return (t ! Transaction.txnDate')
    ) id' max'
  tl <- queryList $ relation $ do
    t <- query Transaction.transaction
    wheres $ t ! Transaction.accountId' .=. proj ! Account.accountId'
    return (value (1 :: Int64))
  Account.lastActivityDate' <-# (toDay $ flattenMaybe ts)
  wheres $ exists $ tl

toDay :: SqlContext c => Record c (Maybe LocalTime) -> Record c (Maybe Day)
toDay dt = unsafeProjectSql $ "date(" ++ unsafeShowSql dt ++ ")"

-- |
-- (original) Deleting data
--
-- Handwritten SQL:
--
-- @
--   DELETE FROM account
--   WHERE account_id = 2;
-- @
--
-- Generated SQL:
--
-- @
--   DELETE FROM MAIN.account WHERE (account_id = 2)
-- @
--
deleteAccount_o1 :: Delete ()
deleteAccount_o1 = deleteNoPH $ \proj -> do
  wheres $ proj ! Account.accountId' .=. value 2

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   DELETE FROM MAIN.account WHERE (account_id = ?)
-- @
--
-- Note: This function is equal to the following:
--
-- @
--   deleteAccount_o1P :: Delete Int64
--   deleteAccount_o1P = derivedDelete $ \proj -> do
--     fmap fst $ placeholder (\ph -> wheres $ proj ! Account.accountId' .=. ph)
-- @
--
deleteAccount_o1P :: Delete Int
deleteAccount_o1P = delete $ \proj -> do
  fmap fst $ placeholder (\ph -> wheres $ proj ! Account.accountId' .=. ph)

-- |
-- (original) Data modification using equality conditions
--
-- Handwritten SQL:
--
-- @
--   DELETE FROM account
--   WHERE account_id >= 10 AND account_id <= 20;
-- @
--
-- Generated SQL:
--
-- @
--   DELETE FROM MAIN.account WHERE ((account_id >= 10) AND (account_id <=
--   20))
-- @
--
deleteAccount_o2 :: Delete ()
deleteAccount_o2 = deleteNoPH $ \proj -> do
  wheres $ proj ! Account.accountId' .>=. value 10
  wheres $ proj ! Account.accountId' .<=. value 20

-- |
-- Placeholder version of Generated SQL:
--
-- @
--   DELETE FROM MAIN.account WHERE ((account_id >= ?) AND (account_id <=
--   ?))
-- @
--
deleteAccount_o2P :: Delete (Int, Int)
deleteAccount_o2P = delete $ \proj -> do
  (phMin,()) <- placeholder (\ph -> wheres $ proj ! Account.accountId' .>=. ph)
  (phMax,()) <- placeholder (\ph -> wheres $ proj ! Account.accountId' .<=. ph)
  return (phMin >< phMax)

-- |
-- 9.4.2 Data manipulation using correlated subqueries
--
-- Handwritten SQL:
--
-- @
--   DELETE FROM department d
--   WHERE NOT EXISTS (SELECT 1
--   FROM employee e
--   WHERE e.dept_id = d.dept_id);
-- @
--
-- Generated SQL:
--
-- @
--   DELETE FROM MAIN.department WHERE (NOT (EXISTS (SELECT ALL 1 AS f0
--   FROM MAIN.employee T0 WHERE (T0.dept_id = dept_id))))
-- @
--
deleteEmployee_9_4_2 :: Delete ()
deleteEmployee_9_4_2 = deleteNoPH $ \proj -> do
  el <- queryList $ relation $ do
    e <- query employee
    wheres $ e ! Employee.deptId' .=. just (proj ! Department.deptId')
    return (value (1 :: Int64))
  wheres $ not' . exists $ el

--
-- run and print sql
--

run :: (Show a, IConnection conn, FromSql SqlValue a, ToSql SqlValue p)
    => conn -> p -> Relation p a -> IO ()
run conn param rel = do
  putStrLn $ "SQL: " ++ show rel
  records <- runRelation conn rel param
  mapM_ print records
  putStrLn ""

runI :: (IConnection conn, ToSql SqlValue p)
     => conn -> p -> Insert p -> IO ()
runI conn param ins = do
  putStrLn $ "SQL: " ++ show ins
  num <- runInsert conn ins param
  print num
  putStrLn ""
  rollback conn

runIQ :: (IConnection conn, ToSql SqlValue p)
     => conn -> p -> InsertQuery p -> IO ()
runIQ conn param ins = do
  putStrLn $ "SQL: " ++ show ins
  num <- runInsertQuery conn ins param
  print num
  putStrLn ""
  rollback conn

runU :: (IConnection conn, ToSql SqlValue p)
     => conn -> p -> Update p -> IO ()
runU conn param upd = do
  putStrLn $ "SQL: " ++ show upd
  num <- runUpdate conn upd param
  print num
  putStrLn ""
  rollback conn

runD :: (IConnection conn, ToSql SqlValue p)
     => conn -> p -> Delete p -> IO ()
runD conn param dlt = do
  putStrLn $ "SQL: " ++ show dlt
  num <- runDelete conn dlt param
  print num
  putStrLn ""
  rollback conn

main :: IO ()
main = handleSqlError' $ withConnectionIO (connectSqlite3 "examples.db") $ \conn -> do
  run conn () allAccount
  run conn () account_3_7
  run conn () account_3_7_1
  run conn () employee_3_7_3
  run conn () employee_4_1_2
  run conn (read "2003-01-01") employee_4_1_2P
  run conn () employee_4_3_2
  run conn (read "2001-01-01", read "2003-01-01") employee_4_3_2P
  run conn () account_4_3_3a
  run conn () account_4_3_3aT
  run conn () account_4_3_3aR
  run conn () account_9_1
  run conn "ACCOUNT" account_4_3_3b
  run conn "ACCOUNT" account_4_3_3bT
  run conn "ACCOUNT" account_4_3_3bR
  run conn () account_4_3_3c
  run conn () join_5_1_2a
  run conn () join_5_1_2aT
  run conn () account_LeftOuterJoin
  putStrLn $ "SQL: " ++ show business_RightOuterJoin -- right join is not supported by SQLite3
  run conn () join_5_1_3
  run conn () selfJoin_5_3a
  run conn () selfJoin_5_3aT
  run conn () union_6_4_1a_Nest
  run conn () union_6_4_1a_Flat
  run conn () group_8_1a
  run conn () customer_9_4
  runI conn () insertBranch_s1
  runI conn branch1 insertBranch_s1P
  runI conn () insertBranch_s1R
  runI conn branchTuple insertBranch_s1PT
  runIQ conn () insertEmployee_s2
  runIQ conn () insertEmployee_s2U
  runIQ conn employee4 insertEmployee_s2P
  runU conn () updateEmployee_o3
  runU conn ("Bush", 3, 10) updateEmployee_o3P
  runU conn () updateAccount_9_4_2
  runD conn () deleteAccount_o1
  runD conn 2 deleteAccount_o1P
  runD conn () deleteAccount_o2
  runD conn (10,20) deleteAccount_o2P
  runD conn () deleteEmployee_9_4_2