MySQL 行列相互转换

行列相互转换

/*创建表*/
CREATE TABLE ic (
    NAME VARCHAR (20),
    Product VARCHAR (20),
    amount INT
);
INSERT INTO ic
VALUES
    ('王一', 'A1', 20),
    ('王一', 'A3', 150),
    ('王一', 'A2', 10),
    ('赵二', 'A1', 52),
    ('赵二', 'A2',46),
    ('赵二', 'A3',78),
    ('刘六', 'A1',55),
    ('刘六', 'A2',20),
    ('刘六', 'A3',86);

SELECT * FROM ic;

想要用product列的值做列，列名变为 name，A1，A2，A3。

CREATE TABLE ic_1
SELECT name ,
SUM(IF(Product='A1',amount,0)) AS A1,
SUM(IF(Product='A2',amount,0)) AS A2,
SUM(IF(Product='A3',amount,0)) AS A3
FROM ic
GROUP BY name;

 如果将ic_1表再变回到原来的样子

SELECT name, 'A1' AS Product, A1 AS amount from ic_1
UNION
SELECT name, 'A2' AS Product, A2 AS amount from ic_1
UNION
SELECT name, 'A3' AS Product, A3 AS amount from ic_1
ORDER BY name;