External Article

Showplan Operator of the Week – BookMark/Key Lookup

Fabiano continues in his mission to describe the major Showplan Operators used by SQL Server's Query Optimiser. This week he meets a star, the Key Lookup, a stalwart performer, but most famous for its role in ill-performing queries where an index does not 'cover' the data required to execute the query. If you understand why, and in what circumstances, key lookups are slow, it helps greatly with optimising query performance.

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Question of the Day

An Unusual Identity

What values are returned when I run this code?

CREATE TABLE dbo.IdentityTest2
(
     id NUMERIC(10,0) IDENTITY(10,10) PRIMARY KEY,
     somevalue VARCHAR(20)
)
GO
INSERT dbo.IdentityTest2
(
    somevalue
)
VALUES
( 'Steve')
, ('Bill')
GO
SELECT top 10
 id
 FROM dbo.IdentityTest2

See possible answers