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  • 11.21

    一、题目描述

    从titles表获取按照title进行分组,每组个数大于等于2,给出title以及对应的数目t。
    CREATE TABLE IF NOT EXISTS "titles" (
    `emp_no` int(11) NOT NULL,
    `title` varchar(50) NOT NULL,
    `from_date` date NOT NULL,
    `to_date` date DEFAULT NULL);
    如插入:
    INSERT INTO titles VALUES(10001,'Senior Engineer','1986-06-26','9999-01-01');
    INSERT INTO titles VALUES(10002,'Staff','1996-08-03','9999-01-01');
    INSERT INTO titles VALUES(10003,'Senior Engineer','1995-12-03','9999-01-01');
    INSERT INTO titles VALUES(10004,'Engineer','1986-12-01','1995-12-01');
    INSERT INTO titles VALUES(10004,'Senior Engineer','1995-12-01','9999-01-01');
    INSERT INTO titles VALUES(10005,'Senior Staff','1996-09-12','9999-01-01');
    INSERT INTO titles VALUES(10005,'Staff','1989-09-12','1996-09-12');
    INSERT INTO titles VALUES(10006,'Senior Engineer','1990-08-05','9999-01-01');
    INSERT INTO titles VALUES(10007,'Senior Staff','1996-02-11','9999-01-01');
    INSERT INTO titles VALUES(10007,'Staff','1989-02-10','1996-02-11');
    INSERT INTO titles VALUES(10008,'Assistant Engineer','1998-03-11','2000-07-31');
    INSERT INTO titles VALUES(10009,'Assistant Engineer','1985-02-18','1990-02-18');
    INSERT INTO titles VALUES(10009,'Engineer','1990-02-18','1995-02-18');
    INSERT INTO titles VALUES(10009,'Senior Engineer','1995-02-18','9999-01-01');
    INSERT INTO titles VALUES(10010,'Engineer','1996-11-24','9999-01-01');
    INSERT INTO titles VALUES(10010,'Engineer','1996-11-24','9999-01-01');

    答案

    select title, count(title) t from titles
    group by title
    having t >=2

    二、题目描述

    从titles表获取按照title进行分组,每组个数大于等于2,给出title以及对应的数目t。
    注意对于重复的emp_no进行忽略(即emp_no重复的title不计算,title对应的数目t不增加)。
    CREATE TABLE IF NOT EXISTS `titles` (
    `emp_no` int(11) NOT NULL,
    `title` varchar(50) NOT NULL,
    `from_date` date NOT NULL,
    `to_date` date DEFAULT NULL);
    如插入:
    INSERT INTO titles VALUES(10001,'Senior Engineer','1986-06-26','9999-01-01');
    INSERT INTO titles VALUES(10002,'Staff','1996-08-03','9999-01-01');
    INSERT INTO titles VALUES(10003,'Senior Engineer','1995-12-03','9999-01-01');
    INSERT INTO titles VALUES(10004,'Engineer','1986-12-01','1995-12-01');
    INSERT INTO titles VALUES(10004,'Senior Engineer','1995-12-01','9999-01-01');
    INSERT INTO titles VALUES(10005,'Senior Staff','1996-09-12','9999-01-01');
    INSERT INTO titles VALUES(10005,'Staff','1989-09-12','1996-09-12');
    INSERT INTO titles VALUES(10006,'Senior Engineer','1990-08-05','9999-01-01');
    INSERT INTO titles VALUES(10007,'Senior Staff','1996-02-11','9999-01-01');
    INSERT INTO titles VALUES(10007,'Staff','1989-02-10','1996-02-11');
    INSERT INTO titles VALUES(10008,'Assistant Engineer','1998-03-11','2000-07-31');
    INSERT INTO titles VALUES(10009,'Assistant Engineer','1985-02-18','1990-02-18');
    INSERT INTO titles VALUES(10009,'Engineer','1990-02-18','1995-02-18');
    INSERT INTO titles VALUES(10009,'Senior Engineer','1995-02-18','9999-01-01');
    INSERT INTO titles VALUES(10010,'Engineer','1996-11-24','9999-01-01');
    INSERT INTO titles VALUES(10010,'Engineer','1996-11-24','9999-01-01');

     答案

    select title,count(distinct(emp_no)) t from titles
    group by title 
    having t>=2
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  • 原文地址:https://www.cnblogs.com/wbf980728/p/14015357.html
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