sql join left联合关联查询实例教程

sql join left联合关联查询实例教程

a表： 结果与数据

studentID  workID  store
1            1      98
1            2      95
2            1      90
2            3      80

b表： 结果与数据
workID  workName 
1        zuoye
2        www.111cn.net
3        wenti

我们要用join left联合查询结果为了如下

studentID  workID  workName  store
1          1      zuoye    98
1          2      shiti    95
或者
studentID  workID  workName  store
2          1      zuoye    98
2          3      wenti    80
*/

$sql ='select a.studentid,a.workid,b.workname from a join b on a.workid=b.workid where a.studentid=1 ';

$sql2 =' select a.studentid,a.workid,b.workname,a.store from a join b on a.workid=b.workid where a.studentid=1 select a.studentid,a.workid,b.workname,a.store from a join b on a.workid=b.workid where a.studentid=2 ';

//数据库教程连接

$db ='fangke_cc';
 mysql教程_pconnect('localhost','root','root') or die(mysql_error());
 mysql_select_db($db);
 mysql_query("set names 'gbk'"); 
 $query = mysql_query($sql);
 while( $rs = mysql_fetch_array( $query ) )
 {
  echo $rs[0],$rs[1],$rs[2];
 }
/*
结果为www.111cn.net
studentID  workID  workName  store
1          1      zuoye    98
1          2      www.111cn.net   95
*/

$query = mysql_query($sql1);
 while( $rs = mysql_fetch_array( $query ) )
 {
  echo $rs[0],$rs[1],$rs[2];
 }
/*
 结果为
 studentID  workID  workName  store
2          1      zuoye    98
2          3      wenti    80