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  • mysql 经典题目

    题目1:实现如下效果

     1 CREATE TABLE IF NOT EXISTS tb_amount(
     2    `Id` INT NOT NULL AUTO_INCREMENT,
     3    `Year` CHAR(4),
     4    `Month` CHAR(2),
     5    `Amount` DECIMAL(5,2),
     6    PRIMARY KEY(`Id`)
     7 );
     8 
     9 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1991', '1', '1.1');
    10 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1991', '2', '1.2');
    11 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1991', '3', '1.3');
    12 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1991', '4', '1.4');
    13 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1992', '1', '2.1');
    14 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1992', '2', '2.2');
    15 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1992', '3', '2.3');
    16 INSERT INTO `tb_amount`(`Year`, `Month`, `Amount`) VALUES('1992', '4', '2.4');
    17 
    18 SELECT `Year`,
    19 (SELECT Amount FROM   tb_amount m WHERE `Month`=1   AND m.`Year`=tb_amount.`Year`) AS m1,
    20 (SELECT Amount FROM   tb_amount m WHERE `Month`=2   AND m.`Year`=tb_amount.`Year`) AS m2,
    21 (SELECT Amount FROM   tb_amount m WHERE `Month`=3   AND m.`Year`=tb_amount.`Year`) AS m3,
    22 (SELECT Amount FROM   tb_amount m WHERE `Month`=4   AND m.`Year`=tb_amount.`Year`) AS m4
    23 FROM tb_amount  GROUP BY `Year`;
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  • 原文地址:https://www.cnblogs.com/h07061108/p/mysql_questions.html
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