Page 71 - SQL

Chapter 20: EXISTS CLAUSE

Examples

EXISTS CLAUSE

Customer Table

Id FirstName LastName

1 Ozgur Ozturk

2 Youssef Medi

3 Henry Tai

Order Table

Id CustomerId Amount

1 2 123.50

2 3 14.80

Get all customers with a least one order

SELECT * FROM Customer WHERE EXISTS (
SELECT * FROM Order WHERE Order.CustomerId=Customer.Id
)

Result

Id FirstName LastName

2 Youssef Medi

3 Henry Tai

Get all customers with no order

SELECT * FROM Customer WHERE NOT EXISTS (
SELECT * FROM Order WHERE Order.CustomerId = Customer.Id
)

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