sql in 转为exists

最新推荐文章于 2024-07-30 04:02:15 发布

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最新推荐文章于 2024-07-30 04:02:15 发布

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分类专栏： sql database 文章标签： sql character collation table structure null

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本文介绍了使用MySQL创建学生和教师两个数据表的过程，并通过SQL语句进行了数据填充。此外，还展示了如何利用IN子句和EXISTS子句进行特定条件下的数据查询。

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-- MySQL dump 10.10 -- -- Host: localhost Database: test -- ------------------------------------------------------ -- Server version 5.0.22-community-nt /*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */; /*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */; /*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */; /*!40101 SET NAMES utf8 */; /*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */; /*!40103 SET TIME_ZONE='+00:00' */; /*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */; /*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */; /*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */; /*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */; -- -- Table structure for table `student` -- DROP TABLE IF EXISTS `student`; CREATE TABLE `student` ( `id` int(11) default NULL, `t_id` int(11) default NULL, `name` varchar(255) default NULL ) ENGINE=InnoDB DEFAULT CHARSET=gbk; -- -- Dumping data for table `student` -- /*!40000 ALTER TABLE `student` DISABLE KEYS */; LOCK TABLES `student` WRITE; INSERT INTO `student` VALUES (1,1,'s1'),(2,1,'s2'),(3,1,'s3'),(4,2,'s44'),(5,2,'s55'),(6,2,'s6'); UNLOCK TABLES; /*!40000 ALTER TABLE `student` ENABLE KEYS */; -- -- Table structure for table `teacher` -- DROP TABLE IF EXISTS `teacher`; CREATE TABLE `teacher` ( `id` int(11) default NULL, `name` varchar(255) default NULL ) ENGINE=InnoDB DEFAULT CHARSET=gbk; -- -- Dumping data for table `teacher` -- /*!40000 ALTER TABLE `teacher` DISABLE KEYS */; LOCK TABLES `teacher` WRITE; INSERT INTO `teacher` VALUES (1,'t1'),(2,'t2'),(3,'t3'); UNLOCK TABLES; /*!40000 ALTER TABLE `teacher` ENABLE KEYS */; /*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */; /*!40101 SET SQL_MODE=@OLD_SQL_MODE */; /*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */; /*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */; /*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */; /*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */; /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */; /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

上面的语名是通过mysqldump -u root -p test >c:/test.sql 导出的

下面是

in 语句

select name from student where t_id in (select t.id from teacher t where t.id<2 );

exists 语句

select s.name from student s where exists (select t.id from teacher t where t.id<2 and s.t_id=t.id);