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Using Subqueries in the FROM Clause in MySQL
How To Use Subqueries in the FROM clause in MySQL?
✍: FYIcenter.com
If you have a query returning many rows of data, and you want to perform another query on those rows, you can put the first query as a subquery in the FROM clause of the second query. A subquery used in this way become a temporary table, and you must provide a table alias name for the subquery as in "SELECT ... FROM (SELECT ...) aliasName". The following statement shows you how to use a subquery as base table for the main query:
mysql> SELECT * FROM (SELECT l.id, l.url, r.comment FROM fyi_links l LEFT OUTER JOIN fyi_rates r ON l.id = r.id) WHERE url LIKE '%er%'; ERROR 1248 (42000): Every derived table must have its own alias mysql> SELECT * FROM (SELECT l.id, l.url, r.comment FROM fyi_links l LEFT OUTER JOIN fyi_rates r ON l.id = r.id) s WHERE s.url LIKE '%er%'; +-----+-------------------+-----------+ | id | url | comment | +-----+-------------------+-----------+ | 101 | dev.fyicenter.com | The best | | 102 | dba.fyicenter.com | Well done | | 103 | sqa.fyicenter.com | Thumbs up | | 107 | www.winrunner.com | NULL | +-----+-------------------+-----------+ 4 rows in set (0.06 sec)
⇒ Counting Groups Returned from GROUP BY in MySQL
⇐ Using Subqueries with the EXISTS Operator in MySQL
2017-12-21, 1373🔥, 0💬
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