Solutions to the Problems in SQL Practice Problems by Sylvia Moestl Vasilik. John Weatherwax

Transcription

1 Solutions to the Problems in SQL Practice Problems by Sylvia Moestl Vasilik John Weatherwax 1

2 Text copyright c 2018 John L. Weatherwax All Rights Reserved Please Do Not Redistribute Without Permission from the Author 2

3 To my family. 3

4 Introduction This is my solution manual to some of the problems in the excellent book: SQL Practice Problems by Sylvia Moestl Vasilik While the original book has solution in SQL Server I found it easiest to work the problems in SQLite and thus these solutions are in that dialect of SQL. I hope you find them useful. /* P 1: */ * Shippers; /* P 2 (EPage 20): */ CategoryName, Description Categories; /* P 3: */ FirstName, LastName, HireDate Employees Title = Sales Representative ; /* P 4 (EPage 25): */ FirstName, LastName, HireDate Employees Title = Sales Representative AND = USA ; /* P 5 (EPage 28): */ OrderID, OrderDate EmployeeID = 5; 4

5 /* P 6 (EPage 32): */ SupplierID, ContactName, ContactTitle Suppliers ContactTitle <> Manager ; /* P 7 (EPage 35): */ ProductID, ProductName Products ProductName LIKE %queso% ; /* P 8 (EPage 38): */ OrderID, CustomerID, Ship Ship IN ( France, Belgium ); /* P 9 (EPage 41): */ OrderID, CustomerID, Ship Ship IN ( Brazil, Mexico, Argentina, Venezuela ); /* P 10 (EPage 44): */ FirstName, LastName, Title, BirthDate Employees BirthDate ASC; 5

6 /* P 11 (EPage 44): */ FirstName, LastName, Title, strftime( %Y-%m-%d, BirthDate) AS DateOnlyBirthDate Employees BirthDate ASC; /* P 12 (EPage 50): */ FirstName, LastName, FirstName LastName AS FullName Employees; /* P 13 (EPage 53): */ OrderID, ProductID, UnitPrice, Quantity, UnitPrice * Quantity AS TotalPrice [Order Details] OrderID, ProductID; /* P 14 (EPage 56): */ COUNT(*) AS Total ; /* P 15 (EPage 59): */ MIN(OrderDate) AS FirstOrder ; /* P 16 (EPage 62): */ 6

7 ; /* P 17 (EPage 65): */ ContactTitle, COUNT(*) AS TotalContractTitle ContactTitle TotalContractTitle DESC; /* P 18 (EPage): */ p.productid, p.productname, s.companyname Products p LEFT JOIN Suppliers s ON p.supplierid = s.supplierid; /* P 19 (EPage 71): */ OrderID, date(orderdate) AS OrderDate, CompanyName LEFT JOIN Shippers ON.ShipVia = Shippers.ShipperID OrderID < OrderID; /* P 20 (EPage 76) */ CategoryName, COUNT(*) AS Count Categories JOIN Products ON Categories.CategoryID = Products.CategoryID CategoryName 7

8 Count DESC; /* P 21 (EPage 79) */, City, COUNT(*) AS Total, City Total DESC; /* P 22 (EPage 82) */ ProductID, ProductName, UnitsInStock, ReorderLevel Products UnitsInStock <= ReorderLevel ProductID; /* P 23 (EPage 85) */ ProductID, ProductName, UnitsInStock, UnitsOnOrder, ReorderLevel, Discontinued Products (UnitsInStock + UnitsOnOrder) <= ReorderLevel AND Discontinued= 0 ProductID; /* P 24 (EPage 88) */ 8

9 CustomerID, CompanyName, Region (CASE WHEN Region IS NULL THEN 1 ELSE 0 END), Region, CustomerID; /* P 25 (EPage 92) */ Ship, AVG(Freight) AS AverageFreight Ship AverageFreight DESC LIMIT 3; /* P 26 (EPage 97) */ Ship, AVG(Freight) AS AverageFreight strftime( %Y, OrderDate) = 1997 Ship AverageFreight DESC LIMIT 3; /* P 28 (EPage 105) */ Ship, AVG(Freight) AS AverageFreight OrderDate >= ( datetime(julianday(max(orderdate)) - 365) ) Ship 9

10 AverageFreight DESC LIMIT 3; /* P 29 (EPage 110) */.EmployeeID, Employees.LastName,.OrderID, Products.ProductName, [Order Details].Quantity LEFT JOIN Employees ON.EmployeeID = Employees.EmployeeID LEFT JOIN [Order Details] ON.OrderID = [Order Details].OrderID LEFT JOIN Products ON [Order Details].ProductID = Products.ProductID.OrderID, [Order Details].ProductID LIMIT 20; /* P 30 (EPage 113) */.CustomerID AS _CustomerID,.CustomerID AS _CustomerID LEFT JOIN ON.CustomerID =.CustomerID.CustomerID IS NULL.CustomerID; /* P 31 (EPage 117) */.CustomerID AS _CustomerID,.CustomerID AS _CustomerID LEFT JOIN ON.CustomerID =.CustomerID AND.EmployeeID = 4.CustomerID IS NULL.CustomerID; 10

11 /* P 32 (EPage 121) */.CustomerID,.CompanyName,.OrderID, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalOrderAmount JOIN ON.CustomerID =.CustomerID JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID,.OrderID HAVING TotalOrderAmount > TotalOrderAmount DESC; /* P 33 (EPage 126) */.CustomerID,.CompanyName, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalOrderAmount JOIN ON.CustomerID =.CustomerID JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID HAVING TotalOrderAmount > TotalOrderAmount DESC; /* P 34 (EPage 129) */.CustomerID,.CompanyName, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalWithoutDiscount, SUM([Order Details].UnitPrice * [Order Details].Quantity * (1-[Order Details].Discount)) AS TotalWithDiscount JOIN ON.CustomerID =.CustomerID 11

12 JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID HAVING TotalWithDiscount > TotalWithDiscount DESC; /* P 35 (EPage 133) */.EmployeeID,.OrderID, date(.orderdate) date(.orderdate, start of month, +1 month, -1 day ) = date(.orderdate).employeeid,.orderid; /* P 36 (EPage 136) */.OrderID, COUNT(.OrderID) AS TotalOrderDetails JOIN [Order Details] ON.OrderID = [Order Details].OrderID.OrderID TotalOrderDetails LIMIT 10; /* P 37 (EPage 139) */ /* To select a fixed number of random rows we can use */ OrderID RANDOM() LIMIT 10; 12

13 /* To select a fixed percentage of random rows we can use */ OrderID RANDOM() LIMIT CAST(0.02 * ( COUNT(*) ) AS INTEGER); /* P 38 (EPage 142) */ OrderID, Quantity, COUNT(*) AS Number [Order Details] Quantity >= 60 OrderID, Quantity HAVING Number > 1; /* P 39 (EPage 146) */ /* Using a CTE (common table expression) */ WITH PossibleOrderIDs AS ( OrderID [Order Details] Quantity >= 60 OrderID, Quantity HAVING COUNT(*) > 1 ) OrderID, ProductID, UnitPrice, Quantity, Discount [Order Details] 13

14 OrderID IN PossibleOrderIDs OrderID, Quantity; /* P 40 (EPage 149) */ For this problem we add the keyword DISTINCT in the statement in the subquery in the provided SQL. /* P 41 (EPage 152) */ OrderID, OrderDate, RequiredDate, ShippedDate ShippedDate >= RequiredDate OrderDate ASC; /* P 42 (EPage 156) */.EmployeeID, Employees.LastName, COUNT(*) As TotalLate JOIN Employees ON.EmployeeID = Employees.EmployeeID ShippedDate >= RequiredDate.EmployeeID, Employees.LastName TotalLate DESC; /* P (EPage 159) */ /* Using two CTE (common table expressions) */ WITH -- Total orders TotalNumberOf AS ( EmployeeID, COUNT(*) AS Total 14

15 EmployeeID ), -- Late orders TotalLate AS ( EmployeeID, COUNT(*) AS TotalLate ShippedDate >= RequiredDate EmployeeID ) DISTINCT.EmployeeID, Employees.LastName, Total, TotalLate, ROUND(CAST(TotalLate AS FLOAT)/Total, 2) AS PercentLate JOIN Employees ON.EmployeeID = Employees.EmployeeID JOIN TotalNumberOf ON.EmployeeID = TotalNumberOf.EmployeeID LEFT JOIN TotalLate ON.EmployeeID = TotalLate.EmployeeID PercentLate DESC; /* P (EPage 177) */ WITH CustomerOrderSizes AS (.CustomerID,.CompanyName, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalOrderAmount JOIN ON.CustomerID =.CustomerID JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID.CustomerID ) 15

16 CustomerID, TotalOrderAmount, CASE WHEN ((TotalOrderAmount > 0) AND (TotalOrderAmount <= 1000)) THEN low WHEN ((TotalOrderAmount > 1000) AND (TotalOrderAmount <= 5000)) THEN medium WHEN ((TotalOrderAmount > 5000) AND (TotalOrderAmount < 10000)) THEN high ELSE very high END AS CustomerGroup CustomerOrderSizes CustomerID; /* P 50 (EPage 185) */ WITH CustomerOrderSizes AS (.CustomerID,.CompanyName, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalOrderAmount JOIN ON.CustomerID =.CustomerID JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID.CustomerID ), CustomerGroups AS ( TotalOrderAmount, CASE WHEN ((TotalOrderAmount > 0) AND (TotalOrderAmount <= 1000)) THEN low WHEN ((TotalOrderAmount > 1000) AND (TotalOrderAmount <= 5000)) THEN medium WHEN ((TotalOrderAmount > 5000) AND (TotalOrderAmount < 10000)) THEN high ELSE very high END AS CustomerGroup CustomerOrderSizes ) CustomerGroup, COUNT(*) AS TotalInGroup, ROUND(CAST(COUNT(*) AS DOUBLE)/( COUNT(*) CustomerGroups), 2) 16

17 AS PercentageInGroup CustomerGroups CustomerGroup PercentageInGroup DESC; /* P 51 (EPage 189) */ WITH CustomerOrderSizes AS (.CustomerID,.CompanyName, SUM([Order Details].UnitPrice * [Order Details].Quantity) AS TotalOrderAmount JOIN ON.CustomerID =.CustomerID JOIN [Order Details] ON.OrderID = [Order Details].OrderID strftime( %Y,.OrderDate) = 1998.CustomerID.CustomerID ), CustomerGroups AS ( CustomerGroupName AS CustomerGroup, TotalOrderAmount CustomerOrderSizes JOIN CustomerGroupThresholds ON (RangeBottom < TotalOrderAmount) AND (TotalOrderAmount <= RangeTop) ) CustomerGroup, COUNT(*) AS TotalInGroup, ROUND(CAST(COUNT(*) AS DOUBLE)/( COUNT(*) CustomerGroups), 2) AS PercentageInGroup CustomerGroups CustomerGroup PercentageInGroup DESC; /* P 52 (EPage 193) */ 17

18 Suppliers UNION ; /* P 53 (EPage 196) */ WITH SupplierCountries AS ( DISTINCT Suppliers ), CustomerCountries AS ( DISTINCT ) -- Using ideas from: SupplierCountries. AS Supplier, CustomerCountries. AS Customer SupplierCountries LEFT JOIN CustomerCountries USING() UNION SupplierCountries. AS Supplier, CustomerCountries. AS Customer CustomerCountries LEFT JOIN SupplierCountries USING() NOT ((Supplier IS NULL) AND (Customer IS NULL)); /* P 54 (EPage 200) */ WITH -- get suppliers countries (and count) SupplierCountries AS ( 18

19 , COUNT(*) AS TotalSuppliers Suppliers IS NOT NULL ), -- get customer countries (and count) CustomerCountries AS (, COUNT(*) AS Total IS NOT NULL ), -- get a union of all countries AllCountries AS ( Suppliers IS NOT NULL UNION IS NOT NULL ) ac., IFNULL(sc.TotalSuppliers, 0) AS TotalSuppliers, IFNULL(cc.Total, 0) AS Total AllCountries ac LEFT JOIN SupplierCountries sc ON ac. = sc. LEFT JOIN CustomerCountries cc ON ac. = cc. ac.; /* P 55 (EPage 204) */ 19

20 -- -- Using ideas from: WITH CountriesFirstOrder AS ( -- get the first order date in each country Ship, MIN(OrderDate) AS FirstOrderDate Ship ) -- select the other information for this first order cfo.ship, CustomerID, OrderID, date(orderdate) AS OrderDate CountriesFirstOrder cfo LEFT JOIN o ON (cfo.firstorderdate = o.orderdate) AND (cfo.ship = o.ship) cfo.ship; /* P 56 (EPage 209) */ io.customerid, io.orderid AS InitialOrderID, date(io.orderdate) AS InitialOrderDate, so.orderid AS NextOrderID, date(so.orderdate) AS NextOrderDate, CAST(julianday(so.OrderDate) - julianday(io.orderdate) AS INTEGER) AS DaysBetween -- io = initial order io -- so = second order JOIN so ON (io.customerid = so.customerid) AND (io.orderid < so.orderid) DaysBetween <= 5; /* P 57 (EPage 217) SQLite does not currently support windowing functions */ 20