Left join vs two queries, which is faster?

Question

Supposing I have two tables to query, which query should I choose?

Left join between them or two separate queries? Which option is faster?

Same question on three tables (so basically double left join vs. three queries), which is faster?

generally I would choose join(s) in a single query, rather than `n`query calls.. — Yohanes Khosiawan 许先汉, May 12 '14 at 08:54
That will depend on the tables, the size of the result sets, the indexes, the queries, the overall architecture, the RDBMS you've chosen, and possibly the phase of the moon. The only real answer here is "it depends." — Matt Gibson, May 12 '14 at 08:56
Each query has an overhead. One join query might end up faster than two separate queries. — Salman A, May 12 '14 at 08:58

score 0 · Answer 1 · answered May 12 '14 at 08:57

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i think only one query is better. But you should try in your SQL Server both queries and see which take a longer time

answered May 12 '14 at 08:57

Daniele94

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Yadhu Krishnan · Accepted Answer · 2014-05-12T09:12:54.683

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Join query is intoduced for faster data fetching..It consumes execution time..So no doubt join query is much faster...When you use seperate query then each time it has to go database and fetch result but when join all queries,it needs only single time travel to db...

edited May 12 '14 at 09:12

answered May 12 '14 at 09:02

Yadhu Krishnan

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Left join vs two queries, which is faster?

2 Answers2