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后缀 _IF 可以附加到任何聚合函数的名称之后。此时,聚合函数会接受一个额外的参数,即条件。

func.max_if(<column>, <cond>)
func.max_if(table.revenue, table.salesperson_id==1).alias('max_revenue_salesperson_1')
| max_revenue_salesperson_1 |
|---------------------------|
| 3000 |
MAX_IF(<column>, <cond>)

创建表并插入示例数据

CREATE TABLE sales (
id INT,
salesperson_id INT,
product_id INT,
revenue FLOAT
);
INSERT INTO sales (id, salesperson_id, product_id, revenue)
VALUES (1, 1, 1, 1000),
(2, 1, 2, 2000),
(3, 1, 3, 3000),
(4, 2, 1, 1500),
(5, 2, 2, 2500);

查询演示:查找 ID 为 1 的销售人员的最大收入

SELECT MAX_IF(revenue, salesperson_id = 1) AS max_revenue_salesperson_1
FROM sales;

结果

| max_revenue_salesperson_1 |
|---------------------------|
| 3000 |