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javamysqlsqlsqlyog

deleting rows in sqlyog having null values

I have a table which dosen't have any key(foreign key and...). Some of table fields have null value. when I use the command: 

DELETE FROM `woe300websnt` WHERE (Arg1=NULL AND Rel=NULL  AND Arg2=NULL);

the query is run successfully but when I use 

select * from woe300websnt

I see that no change is applied and these rows are remained. what is wrong with me?

Solution

  • null is not a value - it's the absence of a value. You cannot use the = operator on it, you need to use the is operator instead:

    DELETE FROM woe300websnt 
WHERE Arg1 IS NULL AND Rel IS NULL AND Arg2 IS NULL;