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This article is to share with you about the usefulness of left semi join in hive. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

LEFT SEMI JOIN is a more efficient implementation of IN/EXISTS subqueries.

Hive currently does not implement IN/EXISTS subqueries, so you can rewrite your subqueries with LEFT SEMI JOIN. The limitation of LEFT SEMI JOIN is that the table on the right in the JOIN clause can only be in the

Filter conditions are set in the ON clause, but not in the WHERE clause, SELECT clause, or anywhere else.

SELECT a.key, a.value FROM a WHERE a.key in (SELECT b.key FROM B)

Can be rewritten as:

SELECT a.key, a.val FROM a LEFT SEMI JOIN b on (a.key = b.key) Thank you for reading! This is the end of this article on "what is the use of left semi join in hive?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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