I have a db with 11 tables.
The tables A
contains 15 fields, 10 of theirs contain an id from another table or the 0 value. Each of these tables has two fields, id
and description
.
I would to query the db to obtain the table A
with the right description
at the place of the id or null if the id is 0.
What do I have to use? join, left or inner join? how?
use this statement to select description & use left join of rest of the tables with tablea:
IF(id = 0, NULL, description)
Example:
SELECT A.* , IF(A.bid = 0, NULL, B.description) , IF(A.cid = 0, NULL, C.description)
from tablea A
LEFT JOIN tableb B on A.bid = B.id
LEFT JOIN tablec C on A.cid = C.id
and so on....
Left join
SELECT * FROM A
LEFT JOIN B ON (A.KEY=B.KEY)
and you get Null when the join isn't possible
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