COUNT_IF

COUNT_IF

后缀 _IF 可以附加到任何聚合函数的名称后。在这种情况下，聚合函数会接受一个额外的参数——条件。

COUNT_IF(<column>, <cond>)

示例

创建表并插入示例数据

CREATE TABLE orders (
  id INT,
  customer_id INT,
  status VARCHAR,
  total FLOAT
);

INSERT INTO orders (id, customer_id, status, total)
VALUES (1, 1, 'completed', 100),
       (2, 2, 'completed', 200),
       (3, 1, 'pending', 150),
       (4, 3, 'completed', 250),
       (5, 2, 'pending', 300);

查询示例：统计已完成订单数

SELECT COUNT_IF(status, status = 'completed') AS completed_orders
FROM orders;

结果

| completed_orders |
|------------------|
|        3         |