Delete sql rows where IDs do not have a match from another table

user_338547 0
Viewed 203369

I'm trying to delete orphan entries in a mysql table.

I have 2 tables like this:

Table files:

| id | ....
------------
| 1  | ....
| 2  | ....
| 7  | ....
| 9  | ....

table blob:

| fileid | ....
------------
| 1  | ....
| 2  | ....
| 3  | ....
| 4  | ....
| 4  | ....
| 4  | ....
| 9  | ....

The fileid and id columns can be used to join the tables together.

I want to delete all rows in table blob where fileid cannot be found in the table files.id.

So using the example above that would delete rows: 3 & 4(s) in the blob table.

mysql sql
4 Answers
DELETE FROM <table> 
WHERE <row column you want to delete by > not in 
(select <column you want to compare other column> from <other table>)

This deletes the row when the first column doesn't appear on the second table

user_30441260
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