v.19.4New Features

Multiple JOINS with Some Restrictions: No Asterisks, No Complex Aliases in On/where/group By/… #4462 (artem Zuikov)

Official CH changelog text
Multiple JOINS with some restrictions: no asterisks, no complex aliases in ON/WHERE/GROUP BY/… #4462 (Artem Zuikov)
Introduces support for multiple JOIN operations in a single query with certain restrictions, such as disallowing asterisks and complex aliases in ON, WHERE, and GROUP BY clauses.

Why it matters

This feature enables users to perform multiple JOINs in queries, expanding the flexibility and expressiveness of data retrieval in ClickHouse while maintaining query optimization and preventing ambiguous or complex aliasing issues that could lead to errors or performance degradation.

How to use it

Users can write queries with multiple JOIN clauses, ensuring they avoid using asterisks for column selection and refrain from applying complex aliases in ON, WHERE, or GROUP BY sections to comply with the restrictions.

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