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How to check a value IS NULL [or] = @param (where @param is null)
Ex:
Select column1 from Table1
where column2 IS NULL => works fine
If I want to replace comparing value (IS NULL) with @param. How can this be done
Select column1 from Table1
where column2 = @param => this works fine until @param got some value in it and if is null never finds a record.
How can this achieve?
376
Let's look at how to use the IS NULL condition in a SELECT statement in SQL Server. For example: SELECT * FROM employees WHERE last_name IS NULL; This SQL Server IS NULL example will return all records from the employees table where the last_name contains a null value.
Generally, NULL data represents data does not exist or missing data or unknown data. IS NULL & IS NOT NULL in SQL is used with a WHERE clause in SELECT, UPDATE and DELETE statements/queries to validate whether column has some value or data does not exist for that column. Please note that NULL and 0 are not same.
null is well-defined value which may represent an unknown value, but it may also represent the absence of a value. It should be up to the developer to decide what null represents, but null itself is absolutely a value and null is null = null.
The ISNULL() function returns a specified value if the expression is NULL. If the expression is NOT NULL, this function returns the expression.
select column1 from Table1
where (@param is null and column2 is null)
or (column2 = @param)
I realize this is an old question, but I had the same one, and came up with another (shorter) answer. Note: this may only work for MS SQL Server, which supports ISNULL(expr,replacement).
SELECT column1 FROM table1
WHERE ISNULL(column2,'') = ISNULL(@param,'')
This also assumes you treat NULL and empty strings the same way.
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