From: Tom Lane <tgl@sss.pgh.pa.us>
To: cpainterwakefield@gmail.com
cc: pgsql-docs@lists.postgresql.org
Subject: Re: clarification on chaining of set operations
In-reply-to: <163338891727.12510.3939775743980651160@wrigleys.postgresql.org>
References: <163338891727.12510.3939775743980651160@wrigleys.postgresql.org>
Comments: In-reply-to PG Doc comments form <noreply@postgresql.org>
	message dated "Mon, 04 Oct 2021 23:08:37 -0000"
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Date: Mon, 04 Oct 2021 19:40:38 -0400
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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