Query not working when looking for null values on the where clause

Question

I got this query that works perfectly:

SELECT FOLDER.folderid, FOLDER.foldername
FROM FOLDER
INNER JOIN COLLABORATORS ON COLLABORATORS.folderid = FOLDER.folderid
WHERE COLLABORATORS.userid = 23

But when I added this on the where clause: "and FOLDER.parent = NULL" it doesnt work. The complete query is:

SELECT FOLDER.folderid, FOLDER.foldername
FROM FOLDER
INNER JOIN COLLABORATORS ON COLLABORATORS.folderid = FOLDER.folderid
WHERE COLLABORATORS.userid = 23 and FOLDER.parent = NULL

Does anyone know whats going on? Thanks

Answer 1

when dealing with NULL, you cannot use = or <> since the values are unknown but instead use IS NULL or IS NOT NULL,

WHERE COLLABORATORS.userid = 23 and FOLDER.parent IS NULL

• MySQL - Working with NULL Values

Answer 2

Change this query

WHERE FOLDER.parent = NULL

to

WHERE FOLDER.parent IS NULL

Because the result of any arithmetic comparison with NULL is also NULL, you cannot obtain any meaningful results from such comparisons.

MySQL Manual

Answer 3

For fetching Null Records from a table, it is required to use where [column] is null. the condition specified in your query FOLDER.parent = NULL, will look for 'NULL' String(word) in the required column. you can check this by inserting 'NULL' string(word) in the above column.