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  • 查询出与jack互为好友的人名字

    建表

    /*
    Navicat MySQL Data Transfer
    
    Source Server         : connect1
    Source Server Version : 50611
    Source Host           : localhost:3306
    Source Database       : db_school
    
    Target Server Type    : MYSQL
    Target Server Version : 50611
    File Encoding         : 65001
    
    Date: 2016-03-23 10:01:57
    */
    
    SET FOREIGN_KEY_CHECKS=0;
    
    -- ----------------------------
    -- Table structure for `t_user`
    -- ----------------------------
    DROP TABLE IF EXISTS `t_user`;
    CREATE TABLE `t_user` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `name` varchar(20) DEFAULT NULL,
      `level` int(11) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;
    
    -- ----------------------------
    -- Records of t_user
    -- ----------------------------
    INSERT INTO `t_user` VALUES ('1', 'jack', '1');
    INSERT INTO `t_user` VALUES ('2', 'tom', '1');
    INSERT INTO `t_user` VALUES ('3', 'jerry', '2');
    INSERT INTO `t_user` VALUES ('4', 'jim', '2');
    INSERT INTO `t_user` VALUES ('5', 'lucy', '3');
    INSERT INTO `t_user` VALUES ('6', 'john', '2');

    /*
    Navicat MySQL Data Transfer
    
    Source Server         : connect1
    Source Server Version : 50611
    Source Host           : localhost:3306
    Source Database       : db_school
    
    Target Server Type    : MYSQL
    Target Server Version : 50611
    File Encoding         : 65001
    
    Date: 2016-03-23 10:02:04
    */
    
    SET FOREIGN_KEY_CHECKS=0;
    
    -- ----------------------------
    -- Table structure for `t_friend`
    -- ----------------------------
    DROP TABLE IF EXISTS `t_friend`;
    CREATE TABLE `t_friend` (
      `f_id` int(11) NOT NULL AUTO_INCREMENT,
      `from_uid` int(11) DEFAULT NULL,
      `to_uid` int(11) DEFAULT NULL,
      PRIMARY KEY (`f_id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;
    
    -- ----------------------------
    -- Records of t_friend
    -- ----------------------------
    INSERT INTO `t_friend` VALUES ('1', '1', '2');
    INSERT INTO `t_friend` VALUES ('2', '1', '3');
    INSERT INTO `t_friend` VALUES ('3', '1', '4');
    INSERT INTO `t_friend` VALUES ('4', '2', '1');
    INSERT INTO `t_friend` VALUES ('5', '2', '3');
    INSERT INTO `t_friend` VALUES ('6', '3', '2');
    INSERT INTO `t_friend` VALUES ('7', '1', '5');
    INSERT INTO `t_friend` VALUES ('8', '5', '1');
    

    #互为好友
    select name from t_user where id in (select t1.to_uid from t_friend t1, t_friend t2 where 
    
    t1.from_uid=t2.to_uid and t1.to_uid=t2.from_uid and t1.from_uid=(select id from t_user where 
    
    t_user.name='jack') and t2.to_uid=(select id from t_user where t_user.name='jack'));


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  • 原文地址:https://www.cnblogs.com/yan456jie/p/5369395.html
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