From: | "Keith Worthington" <keithw(at)narrowpathinc(dot)com> |
---|---|
To: | "PostgreSQL Novice" <pgsql-novice(at)postgresql(dot)org> |
Subject: | CASTING in JOIN or WHERE |
Date: | 2005-02-16 16:47:46 |
Message-ID: | 20050216163641.M46189@narrowpathinc.com |
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Lists: | pgsql-novice |
Hi All,
I have written some SQL and have noticed that PostgreSQL seems to be modifying
the syntax slightly. I do not care per se but if it impacts performance I
want to understand how to write the SQL in the more efficient form. I am
recalling posts commenting on columns with dissimilar types and the lack of
index usage.
I have a column of type varchar
id | character varying(20) | not null
I use this in a WHERE clause
WHERE id = 'SN'
PostgreSQL changes the statement to
WHERE id::text = 'SN'::text
I notice a similar behavior when doing JOINs
Given in table 1
item_id | character varying(20) | not null
and in table 2
id | character varying(20) | not null
The JOIN
ON ( tbl_line_item.item_id = tbl_item.id )
is changed to
ON ( tbl_line_item.item_id::text = tbl_item.id::text )
Kind Regards,
Keith
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