SQL查询以从一个表中获取数据，其中特定列等于另一表中的值

Question

我有两个包含以下列的表（相对于此问题的列子集）

Name: ORDERS
order_id
order_number
grand_total

Name: PURCHASE_ORDERS
purchase_order_id
order_number
supplier

基本上，我正在创建一个搜索函数，该函数可以根据输入过滤掉DataGridView的行，我想知道如何获取查询，该查询将返回以下内容：

伪代码示例-

从订单中选择* WHERE订单编号=（从采购订单中选择订单编号，其中供应商=“测试”）

有时，可以从purchase_orders表中返回多个订单号，这会影响上述查询吗？

Answer 1

你应该用

SELECT* 
   from orders 
WHERE 
   order_number 
IN (SELECT 
       order_number 
    FROM
       purchase_orders 
    WHERE supplier = 'test')

参见： http : //www.tutorialspoint.com/mysql/mysql-in-clause.htm

Answer 2

SELECT
    *
FROM
    orders
WHERE order_number IN (SELECT order_number FROM purchase_orders WHERE supplier = 'test')

或更好

SELECT
    *
FROM
    orders
    LEFT OUTER JOIN purchase_orders ON purchase_orders.order_number = orders.order_number
WHERE
    purchase_orders.supplier = 'test'