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Cant seem to workout what im doing wrong here
SELECT * FROM tbl_imagelabel LEFT OUTER JOIN tbl_image ON tbl_imagelabel.label_id = tbl_image.label_id WHERE tbl_image.label_id is NULL
shows the exact rows I want to delete. but if i change SELECT * FROM to DELETE FROM it doesnt work
DELETE FROM tbl_imagelabel LEFT OUTER JOIN tbl_image ON tbl_imagelabel.label_id = tbl_image.label_id WHERE tbl_image.label_id is NULL
507
Delete left join table is used to delete rows from the left table that do not have matching records in the right table. Below is the syntax to of deleting rows with a left join that does not have matching rows in another table: Delete table1 from table1 LEFT JOIN table2 ON table1. col_name=table2.
We can also use the LEFT JOIN clause in the DELETE statement to delete rows in a table (left table) that does not have matching rows in another table (right table). Note that we only put T1 table after the DELETE keyword, not both T1 and T2 tables like we did with the INNER JOIN clause.
A DELETE statement can include JOIN operations. It can contain zero, one, or multiple JOIN operations. The DELETE removes records that satisfy the JOIN conditions.
For futher reference, on MySQL 5+:
DELETE tbl1.* FROM tbl1 LEFT JOIN tbl2 USING(fld) WHERE tbl2.fld IS NULL;
It'll delete any orphans on TBL1 using fld as join.
GL Paulo Bueno
66
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