SQL Interview Questions

/*

Navicat MySQL Data Transfer

Source Server : localhost

Source Server Version : 50024

Source Host : localhost:3306

Source Database : stu

Target Server Type : MYSQL

Target Server Version : 50024

File Encoding : 65001

Date: 2016-03-22 01:23:27

*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------

-- Table structure for `applycard`

-- ----------------------------

DROP TABLE IF EXISTS `applycard`;

CREATE TABLE `applycard` (

`id` int(11) default NULL,

`applydate` datetime default NULL,

`applyremark` varchar(100) default NULL,

`applynumber` double default NULL

) ENGINE=MyISAM DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of applycard

-- ----------------------------

INSERT INTO `applycard` VALUES ('1', '2016-03-21 23:45:15', 'good', '100');

INSERT INTO `applycard` VALUES ('2', '2016-03-22 23:45:33', 'better', '200');

INSERT INTO `applycard` VALUES ('3', '2016-03-23 23:46:02', 'best', '300');

-- ----------------------------

-- Table structure for `applycarddetail`

-- ----------------------------

DROP TABLE IF EXISTS `applycarddetail`;

CREATE TABLE `applycarddetail` (

`id` int(11) default NULL,

`applyname` varchar(100) default NULL,

`applycardid` varchar(100) default NULL,

`applyaddress` varchar(100) default NULL,

`applynumber` double default NULL

) ENGINE=MyISAM DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of applycarddetail

-- ----------------------------

INSERT INTO `applycarddetail` VALUES ('1', '小明', '11111111111111111', '深圳市', '100');

INSERT INTO `applycarddetail` VALUES ('2', '小强', '22222222222222222', '耒阳市', '200');

INSERT INTO `applycarddetail` VALUES ('4', '小阳', '2222222', '2222222', '300');

INSERT INTO `applycarddetail` VALUES ('5', '小华', '66666666666666666', '小华市', '400');

INSERT INTO `applycarddetail` VALUES ('6', '小花', '66666666666666666', '校花市', '500');

INSERT INTO `applycarddetail` VALUES ('2', '小强', '22222222222222222', '耒阳市', '600');

--查询身份证号码为'11111111111111111的申请日期

#子查询

select applydate from applycard where id=(select id from applycarddetail where applycardid='11111111111111111');

#左连接

select applydate from applycard a left outer join applycarddetail b on (a.id=b.id) where applycardid='11111111111111111';

--删除带“阳”字的记录

delete from applycarddetail where applyname like '阳%';

--删除姓"李"的记录

delete from applycarddetail where applyname like '李%';

--查询身份证出现两条以上的重复记录，并且统计出现次数

select *,count(0) AS 重复次数 from applycarddetail group by applycardid having count(applycardid) >= 2

#select [字段],count(0) AS 重复次数 from[表名] group by [字段] having count([字段]) > 2

--查询无重复记录，根据单个字段查询

select distinct * from applycarddetail order by id desc

#select distinct [字段] from [表名] order by [字段] desc

--同时更新两张表中的申请数量applynumber

--删除表中多余的重复记录，重复记录是根据单个字段来判断