Question

选择SELECT的最佳方法是什么？

我有这张桌子：

t_department ID 名称

t_users ID 名称输入

*类型可以是： 1超级用户 2 normalUser

t_department_superuser （一个部门可以有很多超级用户）

-idSuperUser -idDepartment

t_superuser_normaluser （一个超级用户可以拥有许多normalusers）

-idSuperUser -idNormalUser

最后

t_actions

-id（自动数字） -idUser（这可以是superUser或normalUser的id） -action

给出一个部门名称，例如＆＃34; mainDepartment＆＃34; 我需要从所有normalusers和该部门的所有超级用户的t_actions获取所有记录

我有这个，它有效，但我不是SQL专家（我使用MySQL），我认为这不是选择的最佳方法，而且t_actions将有大量行：

SELECT id,idUser,action
FROM t_actions
WHERE (idUser IN (

SELECT DISTINCT t_department_superuser.idSuperUser FROM t_department
RIGHT JOIN t_department_superuser ON t_department_superuser.idDepartment = t_department.id
LEFT JOIN t_superuser_normaluser ON t_superuser_normaluser.idSuperUser = t_department_superuser.idSuperUser
WHERE name='mainDepartment'


UNION ALL

SELECT DISTINCT t_superuser_normaluser.idNormalUser
FROM t_department
RIGHT JOIN t_department_superuser ON t_department_superuser.idDepartment = t_department.id
LEFT JOIN t_superuser_normaluser ON t_superuser_normaluser.idSuperUser = t_department_superuser.idSuperUser
WHERE name='mainDepartment') 

ORDER BY id;

有什么建议让这更好吗？谢谢!!

Answer 1

因为你正在使用左右连接，所以会有空记录，这就是你需要UNION的原因......你可以通过一个简单的空检查来删除UNION

SELECT id, idUser, action
FROM t_actions
WHERE idUser IN
(   SELECT DISTINCT COALESCE(tsn.idNormalUser, tds.idSuperUser)
    FROM t_department td
    RIGHT JOIN t_department_superuser tds ON tds.idDepartment = td.id
    LEFT JOIN t_superuser_normaluser tsn ON tsn.idSuperUser = tds.idSuperUser
    WHERE td.name='mainDepartment'
)
ORDER BY id;

注意我还在表名中添加了别名，因此更容易写出并读取您尝试选择和加入的列。

修改

使用此表格设计的唯一可行方法是使用数据

SELECT id, idUser, action
FROM t_actions
WHERE idUser IN
((SELECT tds.idSuperUser
  FROM t_department td
  JOIN t_department_superusers tds ON tds.idDepartment = td.id
  WHERE td.name='MAIN')

 UNION
 (SELECT tsn.idNormalUser
  FROM t_department td
  JOIN t_department_superusers tds ON tds.idDepartment = td.id
  JOIN t_superuser_normaluser tsn ON tsn.idSuperUser = tds.idSuperUser
  WHERE td.name='MAIN')
)
ORDER BY id;

Answer 2

SELECT DISTINCT COALESCE(tsn.idNormalUser, tds.idSuperUser)
    FROM t_department td
    RIGHT JOIN t_department_superusers tds ON tds.idDepartment = td.id
    LEFT JOIN t_superuser_normaluser tsn ON tsn.idSuperUser = tds.idSuperUser
    WHERE td.name='MAIN'

返回normalusers列表：2,3,4和5，但不是超级用户（1和6）。我正在尝试的是让所有超级用户和MAIN部门的normalusers在一列返回。

这是带有我拥有的数据（INSERTS）的表的MySQL Dump。 sqlfiddle给了我错误：\

-- MySQL dump 10.13  Distrib 5.6.17, for Win32 (x86)
--
-- Host: localhost    Database: cdcol
-- ------------------------------------------------------
-- Server version   5.5.32

/*!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 `t_department`
--

DROP TABLE IF EXISTS `t_department`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `t_department` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(45) COLLATE latin1_general_ci DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `t_department`
--

LOCK TABLES `t_department` WRITE;
/*!40000 ALTER TABLE `t_department` DISABLE KEYS */;
INSERT INTO `t_department` VALUES (1,'MAIN');
/*!40000 ALTER TABLE `t_department` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `t_department_superusers`
--

DROP TABLE IF EXISTS `t_department_superusers`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `t_department_superusers` (
  `idDepartment` int(11) NOT NULL,
  `idSuperUser` int(11) NOT NULL,
  PRIMARY KEY (`idDepartment`,`idSuperUser`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `t_department_superusers`
--

LOCK TABLES `t_department_superusers` WRITE;
/*!40000 ALTER TABLE `t_department_superusers` DISABLE KEYS */;
INSERT INTO `t_department_superusers` VALUES (1,1),(1,6);
/*!40000 ALTER TABLE `t_department_superusers` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `t_superuser_normaluser`
--

DROP TABLE IF EXISTS `t_superuser_normaluser`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `t_superuser_normaluser` (
  `idSuperUser` int(11) NOT NULL,
  `idNormalUser` int(11) NOT NULL,
  PRIMARY KEY (`idSuperUser`,`idNormalUser`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `t_superuser_normaluser`
--

LOCK TABLES `t_superuser_normaluser` WRITE;
/*!40000 ALTER TABLE `t_superuser_normaluser` DISABLE KEYS */;
INSERT INTO `t_superuser_normaluser` VALUES (1,2),(1,3),(1,4),(1,5),(6,2),(6,3),(6,4),(6,5);
/*!40000 ALTER TABLE `t_superuser_normaluser` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `t_users`
--

DROP TABLE IF EXISTS `t_users`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `t_users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `type` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `t_users`
--

LOCK TABLES `t_users` WRITE;
/*!40000 ALTER TABLE `t_users` DISABLE KEYS */;
INSERT INTO `t_users` VALUES (1,1),(2,2),(3,2),(4,2),(5,2),(6,1);
/*!40000 ALTER TABLE `t_users` ENABLE KEYS */;
UNLOCK TABLES;
/*!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 */;

-- Dump completed on 2014-12-23 18:47:03

在MySQL中执行此SELECT的更好方法

2 个答案: