getAll("SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid WHERE a.id IN ($idin){$orderby}") : array();
getAll("SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid WHERE a.id IN ($idin){$orderby}") : 在这段代码中添加 {$db_mp}cat 中查询 a.catid =c.catid 形式如: `{$db_mp}cat` AS c ON a.catid =c.catid怎么把这个查询加到那段代码里
主要是不懂语法,不知道怎么在这段代码中添加 {$db_mp}cat 中查询 a.catid =c.catid 形式如: `{$db_mp}cat` AS c ON a.catid =c.catid
是的 JOIN `{$db_mp}cat` AS c ON a.catid =c.catid
原串 "SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid WHERE a.id IN ($idin){$orderby}" 目标串 "SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid LEFT JOIN `{$db_mp}cat` AS c ON a.catid =c.catid WHERE a.id IN ($idin){$orderby}"为了看上去清晰点,我把字符串打断了MySQL 推荐这样的写法(内部联合) "SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN (`{$db_mp}area` AS b, `{$db_mp}cat` AS c) ON (a.id = b.areaid and a.catid =c.catid WHERE a.id IN ($idin){$orderby}" 对 mysql 的查询优化很有帮助
getAll("SELECT a.id,a.catid,b.areaname FROM {$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid WHERE a.id IN ($idin){$orderby}") : 在这段代码中添加 {$db_mp}cat 中查询 a.catid =c.catid 形式如: `{$db_mp}cat` AS c ON a.catid =c.catid怎么把这个查询加到那段代码里
主要是不懂语法,不知道怎么在这段代码中添加 {$db_mp}cat 中查询 a.catid =c.catid
形式如: `{$db_mp}cat` AS c ON a.catid =c.catid
"SELECT a.id,a.catid,b.areaname
FROM
{$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid
WHERE a.id IN ($idin){$orderby}"
目标串
"SELECT a.id,a.catid,b.areaname
FROM
{$db_mp}info AS a LEFT JOIN `{$db_mp}area` AS b ON a.id = b.areaid
LEFT JOIN `{$db_mp}cat` AS c ON a.catid =c.catid
WHERE a.id IN ($idin){$orderby}"为了看上去清晰点,我把字符串打断了MySQL 推荐这样的写法(内部联合)
"SELECT a.id,a.catid,b.areaname
FROM
{$db_mp}info AS a LEFT JOIN (`{$db_mp}area` AS b, `{$db_mp}cat` AS c) ON (a.id = b.areaid and a.catid =c.catid
WHERE a.id IN ($idin){$orderby}"
对 mysql 的查询优化很有帮助