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

I have two tables containing the following columns (subset of columns relative to this question)

Name: ORDERS
order_id
order_number
grand_total

Name: PURCHASE_ORDERS
purchase_order_id
order_number
supplier

Basically I am creating a search function that can filter out rows in a DataGridView based on input and I was wondering how I get a query which would return the following:

pseudocode example -

select * from orders WHERE order_number = (select order_number from purchase_orders where supplier = 'test')

sometimes more than one order number can be returned from the purchase_orders table so will that influence the above query?

Answer 1

You should use

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

See: 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')

Or Better

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