From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ben Morrow <ben@morrow.me.uk>
cc: jorgemal1960@gmail.com, pgsql-sql@postgresql.org
Subject: Re: UPDATE query with variable number of OR conditions in WHERE
In-reply-to: <20130314235807.GA81164@anubis.morrow.me.uk>
References: <20130314235807.GA81164@anubis.morrow.me.uk>
Comments: In-reply-to Ben Morrow <ben@morrow.me.uk>
	message dated "Thu, 14 Mar 2013 23:58:11 -0000"
Date: Thu, 14 Mar 2013 23:15:17 -0400
Message-ID: <19955.1363317317@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-sql-owner@postgresql.org

Ben Morrow <ben@morrow.me.uk> writes:
> Quoth jorgemal1960@gmail.com (JORGE MALDONADO):
>> I am building an UPDATE query at run-time and one of the fields I want to
>> include in the WHERE condition may repeat several times, I do not know how
>> many.
>> 
>> UPDATE table1
>> SET field1 = "some value"
>> WHERE (field2 = value_1 OR field2 = value_2 OR .....OR field2 = value_n)
>> 
>> I build such a query using a programming language and, after that, I
>> execute it. Is this a good approach to build such a query?

> You can use IN for this:

>     UPDATE table1
>     SET field1 = "some value"
>     WHERE field2 IN (value_1, value_2, ...);

IN is definitely better style than a long chain of ORs.  Another
possibility is to use = ANY(ARRAY):

    UPDATE table1
    SET field1 = "some value"
    WHERE field2 = ANY (ARRAY[value_1, value_2, ...]);

This is not better than IN as-is (in particular, IN is SQL-standard and
this is not), but it opens the door to treating the array of values as a
single parameter:

    UPDATE table1
    SET field1 = "some value"
    WHERE field2 = ANY ($1::int[]);

(or text[], etc).  Now you can build the array client-side and not need
a new statement for each different number of comparison values.  If
you're not into prepared statements, this may not excite you, but some
people find it to be a big deal.

			regards, tom lane


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