1. 子查询
    

   记录        [3,+2)           从0编号,第三行记录序号为 2
   
   limit offset
   
   

    

    
   子查询
   
   

    

    子查询查出第三行记录的dept_no

   
   导表sql
   
   

   -- MySQL dump 10.13  Distrib 8.0.22, for Win64 (x86_64)
   --
   -- Host: localhost    Database: employees
   -- ------------------------------------------------------
   -- Server version    8.0.22
   
   /*!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 */;
   /*!50503 SET NAMES utf8mb4 */;
   /*!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 `departments`
   --
   
   DROP TABLE IF EXISTS `departments`;
   /*!40101 SET @saved_cs_client     = @@character_set_client */;
   /*!50503 SET character_set_client = utf8mb4 */;
   CREATE TABLE `departments` (
     `dept_no` char(4) NOT NULL,
     `dept_name` varchar(40) NOT NULL,
     PRIMARY KEY (`dept_no`),
     UNIQUE KEY `dept_name` (`dept_name`)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
   /*!40101 SET character_set_client = @saved_cs_client */;
   
   --
   -- Dumping data for table `departments`
   --
   
   LOCK TABLES `departments` WRITE;
   /*!40000 ALTER TABLE `departments` DISABLE KEYS */;
   INSERT INTO `departments` VALUES (‘d009‘,‘Customer Service‘),(‘d005‘,‘Development‘),(‘d002‘,‘Finance‘),(‘d003‘,‘Human Resources‘),(‘d001‘,‘Marketing‘),(‘d004‘,‘Production‘),(‘d006‘,‘Quality Management‘),(‘d008‘,‘Research‘),(‘d007‘,‘Sales‘);
   /*!40000 ALTER TABLE `departments` 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 2021-05-18  9:50:05

   View Code

    

2. join
   

   SELECT
       * 
   FROM
       departments t1
       JOIN ( SELECT dept_no FROM departments ORDER BY dept_no ASC LIMIT 2, 1 ) t2 
   WHERE
       t1.dept_no >= t2.dept_no 
   ORDER BY
       t1.dept_no ASC 
       LIMIT 2

   子查询在索引上完成

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