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What is CONCAT in SQL? String concatenation for beginners

CONCAT means "join strings together". Plain words: three forms (||, CONCAT, CONCAT_WS), how each treats NULL differently, and why CONCAT_WS is the best choice for addresses and names. With tables and common pitfalls.

1 min readSQL · CONCAT · string · tutorial

CONCAT is "join several strings together". Looks impossible to mess up, but SQL has three concatenation forms that handle NULL differently. Inattention leads to "a third of users have NULL full names" bugs.

This article is currently in Russian. The full English translation is on the way.

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