How to Combine Multiple SELECT Statements with LIMIT 1 in SQL?

Combining Multiple SELECT Statements

As you've mentioned, you're facing an issue when attempting to combine multiple SELECT statements that each limit the results to a single row. The challenge arises when using UNION ALL because the LIMIT clause seems to disrupt the union process.

To resolve this, you can employ parentheses to enclose each individual SELECT statement. This ensures the union is performed correctly, as the documentation for UNION explicitly states that ORDER BY and LIMIT clauses must be enclosed within parentheses to apply to the subexpression rather than the result of the union.

Here's how you can modify your query:

(SELECT result FROM foo.table LIMIT 1)
UNION ALL
(SELECT result FROM bar.table LIMIT 1)
UNION ALL
(SELECT result FROM doo.table LIMIT 1)

This syntax ensures that each sub-statement is processed separately, with the LIMIT clause applied to the individual results. The union is then performed on the individual row results, giving you a single column with the expected number of rows to match the schema names.

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