Horton

Re: clarification on chaining of set operations

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: cpainterwakefield@gmail.com
Cc: pgsql-docs@lists.postgresql.org
Date: 2021-10-04T23:40:38Z
Lists: pgsql-docs 
PG Doc comments form <noreply@postgresql.org> writes:
> Regarding section 7.4 of the documentation.  I was curious about the
> behavior when combining different set operations in one query, e.g, 
> query1 op1 query2 op2 query3;
> where op1 and op2 are one of UNION, INTERSECT, EXCEPT.

> The documentation suggests that this is equivalent to 
> (query1 op1 query2) op2 query3;
> but only states it for the case when op1 = op2 = UNION.

The SELECT reference page explains that INTERSECT binds more tightly
than UNION or EXCEPT.  I think it's an oversight that section 7.4
doesn't mention that.

			regards, tom lane

Commits

  1. Doc: improve description of UNION/INTERSECT/EXCEPT syntax.