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Editorial Team
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Asked: 2026-06-04T10:44:16+00:00

I’m using a union query: SELECT snippet_id, title FROM tbl_snippets WHERE title LIKE ?

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I’m using a union query:

SELECT snippet_id, title FROM tbl_snippets WHERE title LIKE ?
UNION
SELECT tag_id, tag FROM tbl_tags WHERE tag LIKE ?
UNION
SELECT category_id, category FROM tbl_categories WHERE category LIKE ?

How will I know which table a result came from?snippet_id, tag_id and category_id doesn’t have a prefix like SN, TG, or CI that I could use to determine where a result came from.
The results are basically put together in one result so I don’t really know if what I’m thinking is possible that’s why I came asking here.

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1 Answer

  1. Editorial Team

    Why not adding the prefix as a separate (computed) column?

    SELECT 'SN' prefix, snippet_id, title FROM tbl_snippets WHERE title LIKE ?
UNION ALL
SELECT 'TA', tag_id, tag FROM tbl_tags WHERE tag LIKE ?
UNION ALL
SELECT 'CA', category_id, category FROM tbl_categories WHERE category LIKE ?

    Edit: I have also changed UNION [DISTINCT] to UNION ALL – for the following reasons:

    • If the original query produces different results for UNION and UNION ALL, introducing the prefix will change the number of result rows.
    • In most cases UNION ALL is slightly faster than UNION DISTINCT.
    • Most people actually want to have UNION ALL.
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