SQL - How to select or delete a column with value equal to null in a query select

Question

I have a table in a Mysql comic that has 5 fields. This would be a model query:

select * from myTable where campo1= 4 and campo2=1 and campo3 =7.

However field 3 may have null value and I would need to select or exclude combinations that involve this value.

Example1:

select * from myTable where campo1= 4 and campo2=1 and campo3 = null.

Exemplo2:

select * from myTable where campo1= 4 and campo2=1 and campo3 <> null.

The problem is that these two examples do not work. I’ve tried to use "null" and 'null' but I can’t select.

Any idea?

Answer 1

In case the campo3 = null and not want to show it:

select * from myTable where campo1= 4 and campo2=1 where campo3 is not null

In case you want to show only when the campo3<>null:

select * from myTable where campo1= 4 and campo2=1 where campo3 is null

Answer 2

Instead of using campo = null try to do it that way:

WHERE campo IS NULL

In the Mysql this expression tests if the field is null. To do the reverse just use the IS NOT NULL.

See working on Sqlfiddle