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mysql分组查询前3

DROP TABLE IF EXISTS `emp`;

CREATE TABLE `emp`  (

  `empno` decimal(4, 0) NOT NULL,

  `ename` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,

  `job` varchar(9) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,

  `mgr` decimal(4, 0) NULL DEFAULT NULL,

  `hiredate` datetime(0) NULL DEFAULT NULL,

  `sal` decimal(7, 2) NULL DEFAULT NULL,

  `comm` decimal(7, 2) NULL DEFAULT NULL,

  `deptno` decimal(2, 0) NULL DEFAULT NULL

) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;


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

-- Records of emp

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

INSERT INTO `emp` VALUES (7369, 'SMITH', 'CLERK', 7902, '1980-12-17 00:00:00', 800.00, NULL, 20);

INSERT INTO `emp` VALUES (7499, 'ALLEN', 'SALESMAN', 7698, '1981-02-20 00:00:00', 1600.00, 300.00, 30);

INSERT INTO `emp` VALUES (7521, 'WARD', 'SALESMAN', 7698, '1981-02-22 00:00:00', 1250.00, 500.00, 30);

INSERT INTO `emp` VALUES (7566, 'JONES', 'MANAGER', 7839, '1981-04-02 00:00:00', 2975.00, NULL, 20);

INSERT INTO `emp` VALUES (7654, 'MARTIN', 'SALESMAN', 7698, '1981-09-28 00:00:00', 1250.00, 1400.00, 30);

INSERT INTO `emp` VALUES (7698, 'BLAKE', 'MANAGER', 7839, '1981-05-01 00:00:00', 2850.00, NULL, 30);

INSERT INTO `emp` VALUES (7782, 'CLARK', 'MANAGER', 7839, '1981-06-09 00:00:00', 2450.00, NULL, 10);

INSERT INTO `emp` VALUES (7788, 'SCOTT', 'ANALYST', 7566, '1982-12-09 00:00:00', 3000.00, NULL, 20);

INSERT INTO `emp` VALUES (7839, 'KING', 'PRESIDENT', NULL, '1981-11-17 00:00:00', 5000.00, NULL, 10);

INSERT INTO `emp` VALUES (7844, 'TURNER', 'SALESMAN', 7698, '1981-09-08 00:00:00', 1500.00, 0.00, 30);

INSERT INTO `emp` VALUES (7876, 'ADAMS', 'CLERK', 7788, '1983-01-12 00:00:00', 1100.00, NULL, 20);

INSERT INTO `emp` VALUES (7900, 'JAMES', 'CLERK', 7698, '1981-12-03 00:00:00', 950.00, NULL, 30);

INSERT INTO `emp` VALUES (7902, 'FORD', 'ANALYST', 7566, '1981-12-03 00:00:00', 3000.00, NULL, 20);

INSERT INTO `emp` VALUES (7934, 'MILLER', 'CLERK', 7782, '1982-01-23 00:00:00', 1300.00, NULL, 10);


SET FOREIGN_KEY_CHECKS = 1;




SELECT

FROM

emp e 

WHERE

( SELECT count( 1 ) FROM emp WHERE deptno = e.deptno AND e.sal < sal ) < 3 

ORDER BY

deptno,

sal


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