- 准备
/*
Navicat Premium Data Transfer
Source Server : root
Source Server Type : MySQL
Source Server Version : 50725
Source Host : localhost:3306
Source Schema : cookbook
Target Server Type : MySQL
Target Server Version : 50725
File Encoding : 65001
Date: 13/03/2019 00:19:17
*/
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for EMP
-- ----------------------------
DROP TABLE IF EXISTS `EMP`;
CREATE TABLE `EMP` (
`EMPNO` int(11) NOT NULL,
`ENAME` varchar(10) DEFAULT NULL,
`JOB` varchar(9) DEFAULT NULL,
`MGR` int(11) DEFAULT NULL,
`HIREDATE` date DEFAULT NULL,
`SAL` int(11) DEFAULT NULL,
`COMM` int(11) DEFAULT NULL,
`DEPTNO` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
-- ----------------------------
-- Records of EMP
-- ----------------------------
BEGIN;
INSERT INTO `EMP` VALUES (7369, 'SMITH', 'CLERK', 7902, '1980-12-17', 800, NULL, 20);
INSERT INTO `EMP` VALUES (7499, 'ALLEN', 'SALESMAN', 7698, '1981-02-20', 1600, 300, 30);
INSERT INTO `EMP` VALUES (7521, 'WARD', 'SALESMAN', 7698, '1981-02-22', 1250, 500, 30);
INSERT INTO `EMP` VALUES (7566, 'JONES', 'MANAGER', 7839, '1981-04-02', 2975, NULL, 20);
INSERT INTO `EMP` VALUES (7654, 'MARTIN', 'SALESMAN', 7698, '1981-09-28', 1250, 1400, 30);
INSERT INTO `EMP` VALUES (7698, 'BLAKE', 'MANAGER', 7839, '1981-05-01', 2850, NULL, 30);
INSERT INTO `EMP` VALUES (7782, 'CLARK', 'MANAGER', 7839, '1981-06-09', 2450, NULL, 10);
INSERT INTO `EMP` VALUES (7788, 'SCOTT', 'ANALYST', 7566, '1982-12-09', 3000, NULL, 20);
INSERT INTO `EMP` VALUES (7839, 'KING', 'PRESIDENT', NULL, '1981-11-17', 5000, NULL, 10);
INSERT INTO `EMP` VALUES (7844, 'TURNER', 'SALESMAN', 7698, '1981-09-08', 1500, 0, 30);
INSERT INTO `EMP` VALUES (7876, 'ADAMS', 'CLERK', 7788, '1983-01-12', 1100, NULL, 20);
INSERT INTO `EMP` VALUES (7900, 'JAMES', 'CLERK', 7698, '1981-12-03', 950, NULL, 30);
INSERT INTO `EMP` VALUES (7902, 'FORD', 'ANALYST', 7566, '1981-12-03', 3000, NULL, 20);
INSERT INTO `EMP` VALUES (7934, 'MILLER', 'CLERK', 7782, '1982-01-23', 1300, NULL, 10);
COMMIT;
SET FOREIGN_KEY_CHECKS = 1;
- 将SQL
SELECT
job,
ename
FROM
EMP
查询结果
转为
- SQL实现
SELECT
max(CASE WHEN job='CLERK' THEN ENAME ELSE NULL END) AS clerks,
MAX(CASE WHEN job='ANALYST' THEN ename ELSE NULL END) AS analysts,
MAX(CASE WHEN job='MANAGER' THEN ENAME ELSE NULL END) AS manager,
MAX(case when job='PRESIDENT' THEN ENAME ELSE NULL END ) AS presidents,
max(case when job='SALESMAN' THEN ENAME ELSE NULL END) AS salesmans
FROM (
SELECT e.JOB,e.ENAME,(
SELECT COUNT(*) FROM emp d WHERE e.job=d.job AND e.empno< d.empno) AS rnk FROM EMP e) x GROUP BY rnk