李琴 wrote:

hi,

I want to find something in wikidb. But I don't exectly know how to use the select statement write in WIKI.

For ecample . DatabaseBase::select ($ table, $ vars, $ conds = '', $ fname = 'Database::select', $ options = array(), $ join_conds = array() )

How can I use this to rewrite ' select * from recentchangs where rc_id in(selcet max(rc_id) from recentchangs group by rc_title) and rc_title='Wiki' '.

Thanks very much!

     vanessa lee

Don't use subselects, they're not supported by MySQL 4.0 which is what we target.

$dbr = wfGetDB( DB_SLAVE );

$max = $dbr->selectField( 'recentchanges', 'max(rc_id)', false, __METHOD__, array( 'GROUP BY' => 'rc_title' );

$res = $dbr->select( 'recentchanges', '*', array( 'rc_id' => $max, 'rc_namespace' => 0, 'rc_title' => 'Wiki', ), __METHOD__ );

foreach ( $res as $row ) { // $row is the result row }

The rc_namespace condition is necessary.

-- Tim Starling

hi.sorry to borther again

I want to ask how to rewrite those statement ,too.

Like '>,<,LIMIT '.

And when I use 'order by ' how to change the order of 'ASC,DESC'?

Thanks very much.

vanessa lee

-----Original Message----- From: Roan Kattouw roan.kattouw@gmail.com To: Wikimedia developers wikitech-l@lists.wikimedia.org Date: Thu, 26 Nov 2009 13:32:10 +0100 Subject: Re: [Wikitech-l] SQL

2009/11/26 Tim Starling tstarling@wikimedia.org:

Don't use subselects, they're not supported by MySQL 4.0 which is what we target.

$dbr = wfGetDB( DB_SLAVE );

$max = $dbr->selectField( 'recentchanges', 'max(rc_id)', false, __METHOD__, array( 'GROUP BY' => 'rc_title' );

$res = $dbr->select( 'recentchanges', '*', array( 'rc_id' => $max, 'rc_namespace' => 0, 'rc_title' => 'Wiki', ), __METHOD__ );

Note that the GROUP BY condition in the first query is unnecessary, and that the whole thing could be rewritten to SELECT * FROM recentchanges WHERE rc_namespace=0 AND rc_title='Wiki' ORDER BY rc_id DESC LIMIT 1;

Roan Kattouw (Catrope)

_______________________________________________ Wikitech-l mailing list Wikitech-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l