SQL Server - NULL

There is a bit of inconsistency in the way SQL Server treats (read it as implements) NULLs. Following are some noteworthy points related to implementation and usage of NULL values in SQL Server:

• 3 possible values of logical expression
  • TRUE
  • FALSE
  • UNKNOWN

• UNKNOWN occurs when a logical expression involves NULL
  • NULL > 2 is UNKNOWN
  • NULL = NULL is UNKNOWN
  • X + NULL is UNKNOWN
  • (NOT (UNKNOWN)) IS UNKNOWN

• Query filters (ON, WHERE, HAVING) treat UNKNOWN as FALSE

• CHECK constraint treat UNKNOWN as TRUE

• During comparison NULL = NULL is treated as not equal

• UNIQUE constraint, UNION, EXCEPT, SORTING and GROUPING treats NULLs as equal

This information is quite handy when you are writing TSQL queries targeting data with NULL values.

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GO – SQL Server

While working on SQL Server we all encounter GO statement quite often. Till today GO statement for me was just an indication sent out to SQL Server utilities about end of a batch of Transact - SQL.

Today while going through MSDN I found a new (surprising) thing about GO. Go can actually take an integer argument. Yes! it is true. Go takes an optional integer argument. Something like this,

GO [count]

As per MSDN,

count is a positive integer. The batch preceding GO will execute the specified number of times.

What this means is, suppose you have a script like the one below,

INSERT INTO TestGO VALUES (10, 'testing go')
GO 5000

Here, INSERT statement will be executed 5000 times and you will end up inserting 5000 records in table.

~eNjOy LiFe~
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SQL Server - Size of Index Table for Each Index

I'm a regular reader of Pinal's SQL Authority blog. Few days back, he posted a puzzle to find index size of each index on table. I was able to solve the puzzle and my solution was one of the two solutions selected by Pinal.

Check it out from here

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SQL Server 2008 - Policy Based Management

Few days back I posted an article on MSDN related to SQL Server 2008 Policy Based Management. Check it our if you are interested in Server 2008 new features.