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For example:
SELECT * FROM table_1 LIMIT 5
LEFT JOIN table_2 AS table_1.id = table_2.id
WHERE 1
Otherwise the engine takes all of table_1 before applying the join, then limiting which can slow the query down massively (with massive tables).
584
Yes, indeed! You can use multiple LEFT JOINs in one query if needed for your analysis.
In MySQL, the LIMIT clause is used with the SELECT statement to restrict the number of rows in the result set. The Limit Clause accepts one or two arguments that are offset and count. The value of both the parameters can be zero or positive integers.
The MySQL LIMIT ClauseThe LIMIT clause is used to specify the number of records to return. The LIMIT clause is useful on large tables with thousands of records. Returning a large number of records can impact performance.
Left joins can increase the number of rows in the left table if there are multiple matches in the right table.
You can do it by joining on a subquery instead of an actual table. Something like this should work:
SELECT * FROM
(SELECT * FROM table_1 LIMIT 5) as subq
LEFT JOIN table_2 ON subq.id = table_2.id WHERE 1
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