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To: "Bill" <bchie@opensys.com.hk>
cc: pgsql-sql@postgresql.org
Subject: Re: Re: DateDiff, IsNull? 
In-reply-to: <9lcrij$15lk$2@news.tht.net> 
References: <9lb25o$psq$1@news.tht.net>
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Comments: In-reply-to "Bill" <bchie@opensys.com.hk>
	message dated "Wed, 15 Aug 2001 11:44:27 +0800"
Date: Wed, 15 Aug 2001 00:35:00 -0400
Message-ID: <24829.997850100@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
X-Archive-Number: 200108/203
X-Sequence-Number: 4435

"Bill" <bchie@opensys.com.hk> writes:
> IsNull work like this
> SELECT IsNull( user_name, '') FROM user ;
> then the query will return empty string when the field user_name is null

Apparently, IsNull is Microsoft-speak for the SQL standard's COALESCE
function.  COALESCE is defined as returning the first of its parameters
that is not NULL.

			regards, tom lane