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sqliteleft-joinsql-delete

Deleting rows from SQLite table when no match exists in another table

I need to delete rows from an SQLite table where their row IDs do not exist in another table. The SELECT statement returns the correct rows:

SELECT * FROM cache LEFT JOIN main ON cache.id=main.id WHERE main.id IS NULL;

However, the delete statement generates an error from SQLIte:

DELETE FROM cache LEFT JOIN main ON cache.id=main.id WHERE main.id IS NULL;

The error is: SQLite Error 1 - near "left": syntax error. Is there another syntax I could use?

Solution

  • SQLite apparently doesn't support joins with the delete statement, as you can see on the Syntax diagrams. You should however be able to use a subquery to delete them.

    ie. 

    DELETE FROM cache WHERE id IN
(SELECT cache.id FROM cache LEFT JOIN main ON cache.id=main.id WHERE main.id IS NULL);

    (Not tested)