SQL NULL Archives - Page 4 of 4 - SQL Authority with Pinal Dave

SQL SERVER – Explanation and Understanding NOT NULL Constraint

October 15, 2007

SQL, SQL Performance, SQL Server, SQL Tips and Tricks

SQL Constraint and Keys, SQL Joins, SQL NULL, SQL Scripts

NOT NULL is integrity CONSTRAINT. It does not allow creating of the row where column contains NULL value. Most discussed question about NULL is what is NULL? I will not go in depth analysis it. Simply put NULL is unknown or missing data. When NULL is present in database columns,…

SQL SERVER – Explanation and Comparison of NULLIF and ISNULL

June 22, 2007

Pinal Dave

SQL Tips and Tricks

DBA, SQL Function, SQL NULL, SQL Scripts, SQL Server

Explanation of NULLIF
Syntax:
NULLIF ( expression , expression )

Returns a null value if the two specified expressions are equal. NULLIF returns the first expression if the two expressions are not equal. If the expressions are equal, NULLIF returns a null value of the type of the first expression. NULLIF is equivalent to a searched CASE function in which the two expressions are equal and the resulting expression is NULL.

SQL SERVER – LEN and DATALENGTH of NULL Simple Example

June 12, 2007

Pinal Dave

SQL, SQL Performance, SQL Server, SQL Tips and Tricks

SQL Function, SQL NULL, SQL Scripts

Simple but interesting – In recent survey I found that many developers making this generic mistake. I have seen following code in periodic code review. (The code below is not actual code, it is simple sample code) DECLARE @MyVar VARCHAR(10) SET @MyVar = NULL IF (LEN(@MyVar) = 0) … I…