Question

我正在处理需要比较两个值的存储过程。这是我的sql代码

SELECT customer_id, max_rentals
FROM accounting inner join rental_plans
ON accounting.rental_plan_id = rental_plans.rental_plan_id
WHERE customer_id = 0

返回：

customer_id max_rentals
----------- -----------
0           3

我想写一份声明，说明如果客户0的最大租金价值是3，那么就做点什么。如何在条件语句中引用该值？

提前致谢。

Answer 1

这会按预期工作吗？

UPDATE <table>
SET <update field>=<value>
WHERE <table>.Customer_id IN (
    SELECT customer_id
    FROM accounting inner join rental_plans
    ON accounting.rental_plan_id = rental_plans.rental_plan_id
    WHERE max_rentals=3
)

Answer 2

我认为你正在努力实现这样的目标。

使用case语句，您可以检查max_rentals = 3然后执行某些操作。

SELECT customer_id, max_rentals,
case   when max_rentals=3 then 'do something' else max_rentals end
FROM   accounting inner join rental_plans
ON     accounting.rental_plan_id = rental_plans.rental_plan_id
WHERE  customer_id = 0;

引用select语句的结果

2 个答案: