Re: How to do similar query like Oracle using not exists

[Benjamin Pflugmann <benjamin-mysql@xxxxxxxxxxxx>]

Hi.

On Mon, Dec 03, 2001 at 06:24:14PM -0500, Wai.Lee@xxxxxxxxxx wrote:
> 
> I try to do an Oralce query in mySQL
> 
> insert into geoTable select '011852','HK' from dual where not exists
> (select * from geoTable where geoID = '011852')
> 
> In Oracle, this query will check the new geoID is not exist before
> inserting into the table.
> 
> In mySQL, I do
> 
> create temporary table tmp1 select '011852' geoID, 'HK' countryName;
> create temporary table tmp2 select a.geoID, a.countryName from tmp1 a
> left join geoTable b on a.geoID = b.geoID where a.geoID is null;
> insert into geoTable select * from tmp2; 
> 
> 
> Do anyone know mySQL has a similar function like Oracle to check "NOT
> EXISTS" or there is a better queries than what I use here.

Yes, use a LEFT JOIN and check for NOT NULL in the result.

This is even covered by the fine manual:
http://www.mysql.com/doc/A/N/ANSI_diff_Sub-selects.html

Btw, it is the forth hit if you feed the search engine with simply
"not exists" (the way I got the URL).

Bye,

	Benjamin.

-- 
benjamin-mysql@xxxxxxxxxxxx

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