Question

我这里有2个SQL连接，一个返回好结果，另一个返回0结果集。 为什么会这样？除了连接/列/表顺序之外，它们非常相似。（顺便说一句，我在这里使用MySQL）

工作加入（返回超过240,000行良好数据）

SELECT 
   t1.email AS "email", 
   t1.record_id AS "record_id", 
   t2.status AS "status",
   t3.item_record_id AS "item_record_id",
   t1.ordered_at AS "started_at"

FROM `rs_orders` t1 

INNER JOIN `cb_all_transactions` t2 
ON t1.record_id = CONCAT('cb_sl_', t2.receipt) 

INNER JOIN `rs_order_items` t3
ON t1.record_id = t3.order_record_id

WHERE t2.recurring = 'true' 

ORDER BY t1.ordered_at ASC

非工作加入（返回0行）

SELECT 
   t1.email AS "email", 
   t1.record_id AS "record_id",
   t1.ordered_at AS "started_at",
   t2.item_record_id AS "item_record_id",
   t3.status AS "status"

FROM rs_orders t1

INNER JOIN rs_order_items t2
ON t1.record_id = t2.order_record_id

INNER JOIN cb_all_transactions t3
ON t2.order_record_id = CONCAT('cb_sl_' + t3.receipt)

WHERE t3.recurring = 'true'

Answer 1

他们不一样。第二个是CONCAT('cb_sl_' + t3.receipt)。将+替换为,。

为什么这个SQL连接按顺序工作而不是另一个？

1 个答案: