1. Advanced Joins
IN ( ) Expression
Subqueries with IN ( ) Expression
Left, Right, Full Outer Joins
LEFT ( ), RIGHT ( ), LTRIM ( ), RTRIM ( ) Functions
UNION Queries

2. The IN ( ) Expression
The IN ( ) Expression can work like a simplified OR test in a WHERE clause
Try these two queries
SELECT *
FROM Products
WHERE SupplierID IN (28, 18, 27)
WHERE SupplierID = 28
OR SupplierID = 18
OR SupplierID = 27

3. Try these three queries
Subqueries with IN ( )
Try these three queries
SELECT Products.*
FROM Products INNER JOIN Suppliers
ON Products.SupplierID = Suppliers.SupplierID
WHERE Country = 'France'
SELECT SupplierID
FROM Suppliers
SELECT *
FROM Products
WHERE SupplierID IN (
WHERE Country = 'France')
Subquery

4. Subqueries with IN ( ) (cont.)
Subqueries always execute first
Subqueries may be nested
Subqueries must return a single column
Subquery return values must be compatible with those of the field being tested
Compatible (same) value types
SELECT *
FROM Products
WHERE SupplierID IN (
SELECT SupplierID
FROM Suppliers
WHERE Country = 'France')
Single Column

5. Subquery Advantages—Efficiency
How are the executions of these two queries different?
Display all products purchased by customer 'Around the Horn' in 1997 using nested subqueries
SELECT Products.*
FROM Products INNER JOIN Suppliers
ON Products.SupplierID = Suppliers.SupplierID
WHERE Country = 'France'
SELECT *
FROM Products
WHERE SupplierID IN (
SELECT SupplierID
FROM Suppliers
WHERE Country = 'France')

6. Subquery Advantages—Unary Relationships
Do you remember this? Write the SQL to retrieve the name of Robert King's supervisor
SELECT Sup.FirstName, Sup.LastName
FROM Employees Emp INNER JOIN
Employees Sup
ON Emp.ReportsTo = Sup.EmployeeID
WHERE Emp.LastName = 'King'
AND Emp.FirstName = 'Robert'

7. Subquery Advantages—Unary Relationship (cont.)
Rewrite as a subquery
Use a subquery to find the names of all of the employees that Steven Buchanan supervises
SELECT FirstName, LastName
FROM Employees
WHERE EmployeeID IN (
SELECT ReportsTo
WHERE FirstName = 'Robert'
AND LastName = 'King')

8. Subquery Advantages—No Direct Test
Write a query to find the company names of all customers who placed orders in May of 1997 Hint: Use a Subquery
Now write a query to find the company names of all customers who did not place an order in May of 1997
SELECT CompanyName
FROM Customers
WHERE CustomerID IN (
SELECT DISTINCT CustomerID
FROM Orders
WHERE DatePart(mm, OrderDate) = 5
AND DatePart(yy, OrderDate) = 1997)

9. Subquery Advantages—No Direct Test (cont.)
Write a query to list the names of all products that are not discontinued that were not sold during May of 1997

10. Left (and Right) Outer Joins
You will often want to list all records in one table as well as related records in a second, even if there are no related records in the second table
Execute the following query
Write a query to show all category names along with matching product names
How can we get our new category to show?
INSERT INTO Categories (
CategoryName, Description)
VALUES('Test Category', 'An artificial category added for testing')

11. Left (and Right) Outer Joins (cont.)
SELECT CategoryName, ProductName
FROM Categories LEFT JOIN Products
ON Categories.CategoryID = Products.CategoryID
The query above returns all category names and matching product names if there is a matching product
When there is no matching product a Null is returned
All Category records are returned because Categories is on the Left in the LEFT JOIN expression
Right JOIN would reverse the logic

12. Left (and Right) Outer Joins (cont.)
Run these two queries—What's wrong here?
SELECT CompanyName, OrderDate
FROM Customers LEFT JOIN Orders
ON Customers.CustomerID = Orders.CustomerID
ORDER BY CompanyName, OrderDate
WHERE DatePart(mm, OrderDate) = 5
AND DatePart(yy, OrderDate) = 1997

13. Left (and Right) Outer Joins (cont.)
Where clause type filters must be applied in a special way in outer joins
Add the row-limiting criteria expressions as part of the join criteria
Write a query to list all Employees along with orders they made in 1998
SELECT CompanyName, OrderDate
FROM Customers LEFT JOIN Orders
ON Customers.CustomerID = Orders.CustomerID
AND DatePart(mm, OrderDate) = 5
AND DatePart(yy, OrderDate) = 1997
ORDER BY CompanyName, OrderDate

14. The Full Outer Join
SELECT Emp.LastName AS 'Emp Last', Emp.FirstName AS 'Emp First',
Sup.LastName AS 'Sup Last', Sup.FirstName AS 'Sup First'
FROM Employees Emp FULL JOIN Employees Sup
ON Emp.ReportsTo = Sup.EmployeeID

15. Functions of the Day
LEFT ( ) and RIGHT ( ) return a specified number of characters from the left or right sides of a string
SELECT FirstName, Left(FirstName, 1) + '.' AS 'Initial'
FROM Employees

16. Functions of the Day (cont.)
LTRIM and RTRIM remove Leading/Trailing spaces from a string
When did I need to use this SQL?
UPDATE LastName
SET LastName = LTRIM(LastName)

17. Union Queries
A Union Query allows you to append the results of two different queries and return them as two result sets
Try this:
SELECT CAST(SupplierID AS char(10)) AS 'ID',
CompanyName, 'Supplier' AS 'Type'
FROM Suppliers
UNION
SELECT CAST(CustomerID AS char(10)) AS 'ID',
CompanyName, 'Customer' AS 'Type'
FROM Customers

18. UNION Queries (cont.)
All components queries of a Union query must return:
The same number of columns
Compatible column data types
Use CAST function when necessary
The same column names
Use AS to rename columns when necessary
UNION is particularly useful when combining current and archived (or other partitioned) data into one result set
Write a query to return the names of all people in the Northwinds DB along with their phone numbers