Select rows where column is null

Question

How do you write a SELECT statement that only returns rows where the value for a certain column is null?

Answer 1

You want to know if the column is null

select * from foo where bar is null

If you want to check for some value not equal to something and the column also contains null values you will not get the columns with null in it

does not work:

select * from foo where bar <> 'value'

does work:

select * from foo where bar <> 'value' or bar is null

in Oracle (don't know on other DBMS) some people use this

select * from foo where NVL(bar,'n/a') <> 'value'

if I read the answer from tdammers correctly then in MS SQL Server this is like that

select * from foo where ISNULL(bar,'n/a') <> 'value'

in my opinion it is a bit of a hack and the moment 'value' becomes a variable the statement tends to become buggy if the variable contains 'n/a'.