SQL查詢以從一個表中獲取數據，其中特定列等於另一表中的值

Question

我有兩個包含以下列的表（相對於此問題的列子集）

Name: ORDERS
order_id
order_number
grand_total

Name: PURCHASE_ORDERS
purchase_order_id
order_number
supplier

基本上，我正在創建一個搜索函數，該函數可以根據輸入過濾掉DataGridView的行，我想知道如何獲取查詢，該查詢將返回以下內容：

偽代碼示例-

從訂單中選擇* WHERE訂單編號=（從采購訂單中選擇訂單編號，其中供應商=“測試”）

有時，可以從purchase_orders表中返回多個訂單號，這會影響上述查詢嗎？

Answer 1

你應該用

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

參見： 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'