mysql - Using an alias within a join -

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i'm trying use sql alias within left join. while using alias in join, error 'unknown a_alias column in on clause' point me in right direction?

select a_alias table_a left join table_b on a_alias = b

cheers

you can't use alias in or join hasn't been evaluated yet. they're available in aggregates , group by/order by/having clauses iirc.


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