MySQL中实现行列转换的操作示例

CREATE TABLE t_sales (  
    id int primary key auto_increment,
    col_year INT,  
    product VARCHAR(255),  
    amount DECIMAL(10, 2)  
);  
  
INSERT INTO t_sales (col_year, product, amount) VALUES  
(2020, 'A001', 100),  
(2020, 'B001', 120),  
(2021, 'A001', 150),  
(2021, 'B001', 150),
(2022, 'A001', 260),  
(2022, 'B001', 240),
(2023, 'B001', 330),
(2024, 'A001', 440);

(root@localhost:mysql.sock)[superdb 10:49:26]>select * from t_sales;
+----+----------+---------+--------+
| id | col_year | product | amount |
+----+----------+---------+--------+
|  1 |     2020 | A001    | 100.00 |
|  2 |     2020 | B001    | 120.00 |
|  3 |     2021 | A001    | 150.00 |
|  4 |     2021 | B001    | 150.00 |
|  5 |     2022 | A001    | 260.00 |
|  6 |     2022 | B001    | 240.00 |
|  7 |     2023 | B001    | 330.00 |
|  8 |     2024 | A001    | 440.00 |
+----+----------+---------+--------+
8 rows in set (0.00 sec)

SELECT   
    col_year,  
    SUM(CASE WHEN product = 'A001' THEN amount ELSE 0 END) AS 'A_product',  
    SUM(CASE WHEN product = 'B001' THEN amount ELSE 0 END) AS 'B_product'  
FROM t_sales
GROUP BY col_year;

(root@localhost:mysql.sock)[superdb 10:50:29]>SELECT   
    ->     col_year,  
    ->     SUM(CASE WHEN product = 'A001' THEN amount ELSE 0 END) AS 'A_product',  
    ->     SUM(CASE WHEN product = 'B001' THEN amount ELSE 0 END) AS 'B_product'  
    -> FROM t_sales
    -> GROUP BY col_year;
    
-- 这将返回以下结果
+----------+-----------+-----------+
| col_year | A_product | B_product |
+----------+-----------+-----------+
|     2020 |    100.00 |    120.00 |
|     2021 |    150.00 |    150.00 |
|     2022 |    260.00 |    240.00 |
|     2023 |      0.00 |    330.00 |
|     2024 |    440.00 |      0.00 |
+----------+-----------+-----------+
5 rows in set (0.00 sec)

CREATE TABLE t_pivoted_sales (  
    id int primary key auto_increment,
    col_year INT,  
    A_product DECIMAL(18, 2),  
    B_product DECIMAL(18, 2)  
);  
  
INSERT INTO t_pivoted_sales (col_year, A_product, B_product) VALUES  
(2020, 100.00, 120.0),  
(2021, 150.00, 150.00),
(2022, 260.00, 240.00),
(2023, 0.00, 330.00),
(2024, 440.00, 0.00);

(root@localhost:mysql.sock)[superdb 11:02:54]>select * from t_pivoted_sales;
+----+----------+-----------+-----------+
| id | col_year | A_product | B_product |
+----+----------+-----------+-----------+
|  1 |     2020 |    100.00 |    120.00 |
|  2 |     2021 |    150.00 |    150.00 |
|  3 |     2022 |    260.00 |    240.00 |
|  4 |     2023 |      0.00 |    330.00 |
|  5 |     2024 |    440.00 |      0.00 |
+----+----------+-----------+-----------+
5 rows in set (0.00 sec)

SELECT col_year, 'A_product' AS product, A_product AS amount FROM t_pivoted_sales
union all
SELECT col_year, 'B_product' AS product, B_product AS amount FROM t_pivoted_sales
order by col_year;