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How to know that a field is empty ??? [message #20488]

Wed, 29 May 2002 01:57

hug
Messages: 6
Registered: May 2002

Junior Member

Hi,

i want to create a SQL query that go in a table and delete all the records that contains a empty field.

For example, I have a table named tb with 3 fields a,b,c.
I want to create a query that delete all the records where the field c is empty (c is a String type).
I have try this thing :
DELETE FROM tb WHERE c=''
or this other thing
DELETE FROM tb WHERE c=' '
or this
DELETE FROM tb WHERE c=null
but it doesn't work ...

So my question is :
How to know in SQL that a field of a table is empty.
Is there a function or a keyword ???

Thanks for response
Hugues

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Re: How to know that a field is empty ??? [message #20489 is a reply to message #20488]

Wed, 29 May 2002 02:27

Maaher
Messages: 7065
Registered: December 2001

Senior Member

The correct syntax is:
DELETE FROM tb WHERE c IS null;

Null is the absence of a value, and an absence of a value cannot be compared, even not with another "absence of a value" (i.e. NULL).

MHE

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