Added Multiple Joins Emulation (allow_experimental_multiple_joins_emulation Setting)

Why it matters

This feature addresses the limitation in ClickHouse where multiple JOINs were not natively supported or had restrictions. By enabling this emulation, users can perform complex queries involving multiple JOIN operations, improving query expressiveness and compatibility with SQL standards.

How to use it

To use this feature, enable the experimental setting allow_experimental_multiple_joins_emulation in your ClickHouse configuration or session settings. Once enabled, you can write queries with multiple JOIN clauses which will be internally emulated by ClickHouse.