SQL触发器检查行是否已经存在

Question

所以我有两个表（orders和fabric_order）。在另一个表上完成插入后，将触发此sql。我不希望重复的行，所以我想检查表（fabric_orders）是否已包含一行代码，该行的代码等于其他表（订单）中的代码，并且仅当不存在该行时才插入表（fabric_order）中。相同的代码

IF NOT EXISTS
(
    select code 
    from orders
    WHERE code=fabric_order.code
)
INSERT INTO fabric_order (order_id, code, start_date)
SELECT(id, code, deliver_date)
FROM orders

Answer 1

您不需要触发它，INSERT ... SELECT ... LEFT JOIN ..也应具有相同的结果。

INSERT INTO fabric_order AS fabric_order_outer (
     fabric_order_outer.order_id
   , fabric_order_outer.code
   , fabric_order_outer.start_date
)
SELECT(
     orders.id
   , orders.code
   , orders.deliver_date
)
FROM orders
LEFT JOIN 
  fabric_order AS fabric_order_inner
ON
 orders.code = fabric_order_inner.code
WHERE
 fabric_order_inner.order_id IS NULL