mysql 经典题目

题目1:实现如下效果

mysql 经典题目

mysql 经典题目
 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`;
mysql 经典题目

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mysql 经典题目

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