mysql left join 多个表 博客分类： database MySQLSQLSQL ServerCC++

SQL:

select * from t_a a left join t_b b on a.bid = b.bid left join t_c c on a.cid = c.cid

 

t_a表

t_b表 

 t_c表

总的结果:

 

==============================================================

t_a表

 

t_b表

 

t_c表

 

总的结果表:

 

第二次带数据的sql:

 

# MySQL-Front 3.2  (Build 14.3)

/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE='SYSTEM' */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE */;
/*!40101 SET SQL_MODE='STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES */;
/*!40103 SET SQL_NOTES='ON' */;


# Host: 127.0.0.1    Database: jointest
# ------------------------------------------------------
# Server version 5.0.22-community-nt

DROP DATABASE IF EXISTS `jointest`;
CREATE DATABASE `jointest` /*!40100 DEFAULT CHARACTER SET utf8 */;
USE `jointest`;

#
# Table structure for table t_a
#

CREATE TABLE `t_a` (
  `aid` int(11) NOT NULL auto_increment,
  `aname` varchar(11) default NULL,
  `bid` int(11) default NULL COMMENT '引用自t_b的bid',
  `cid` int(11) default NULL COMMENT '引用自t_c的cid',
  PRIMARY KEY  (`aid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

#
# Dumping data for table t_a
#

INSERT INTO `t_a` VALUES (1,'a名字1',1,1);
INSERT INTO `t_a` VALUES (2,'a名字2',NULL,2);

#
# Table structure for table t_b
#

CREATE TABLE `t_b` (
  `bid` int(11) NOT NULL auto_increment,
  `bname` varchar(11) default NULL,
  PRIMARY KEY  (`bid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

#
# Dumping data for table t_b
#

INSERT INTO `t_b` VALUES (1,'b名字');

#
# Table structure for table t_c
#

CREATE TABLE `t_c` (
  `cid` int(11) NOT NULL auto_increment,
  `cname` varchar(11) default NULL,
  PRIMARY KEY  (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

#
# Dumping data for table t_c
#

INSERT INTO `t_c` VALUES (1,'c名字');
INSERT INTO `t_c` VALUES (2,'c名字2');

/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;