MySQL左连接并有特定条件

Question

我有下表管理收入

收入表

+------------+--------+--------+
| revenue_id | amount | status |
+------------+--------+--------+
|          1 |  45000 |      1 |
|          2 |  25000 |      1 |
|          3 |  67000 |      1 |
|          4 |  22000 |      1 |
|          5 |  32000 |      0 |
+------------+--------+--------+

银行桌

+---------+--------+-------------+-------------+
| bank_id | ref_no | bank_amount | bank_status |
+---------+--------+-------------+-------------+
|       1 |      2 |       23000 | Pending     |
|       2 |      3 |       67000 | Confirmed   |
|       3 |      4 |       22000 | Confirmed   |
+---------+--------+-------------+-------------+

02）如果收入表中提到的收入已经存入银行，则将其记录在银行表中。之后，两个表中的金额相等，银行状态可能会变成“已确认”。

03）因此，我需要通过连接上面的两个表来获取确认记录，如下所示：

所需的输出

+------------+--------+-------------+-------------+
| revenue_id | amount | bank_amount | bank_status |
+------------+--------+-------------+-------------+
|          3 |  67000 |       67000 | Confirmed   |
|          4 |  22000 |       22000 | Confirmed   |
+------------+--------+-------------+-------------+ 

所需的输出-02

+------------+--------+-------------+-------------+
| revenue_id | amount | bank_amount | bank_status |
+------------+--------+-------------+-------------+
|          1 |  45000 |             |             |
|          2 |  25000 |       23000 | Pending     |
|          3 |  67000 |       67000 | Confirmed   |
|          4 |  22000 |       22000 | Confirmed   |
+------------+--------+-------------+-------------+

所需的输出03

+------------+--------+-------------+-------------+
| revenue_id | amount | bank_amount | bank_status |
+------------+--------+-------------+-------------+
|          1 |  45000 |             |             |
|          2 |  25000 |       23000 | Pending     |
+------------+--------+-------------+-------------+

04）为了获得所需的输出，我使用了以下查询

select revenue.revenue_id, revenue.amount, bank.bank_amount, bank.bank_status 
from revenue
left join bank on bank.ref_no = revenue.revenue_id
where revenue.status = 1 and bank.bank_status = "Confirmed"

05）但是没有得到预期的结果。它仅生成空结果。我不明白我要怎么做。有人可以帮我吗？

Answer 1

您必须使用内部联接而不是左联接来获得预期的输出。

SELECT revenue.revenue_id,
       revenue.amount,
       bank.bank_amount,
       bank.bank_status
FROM revenue
INNER JOIN bank ON bank.ref_no = revenue.revenue_id
WHERE revenue.status = 1
  AND bank.bank_status = "Confirmed"

DEMO

Answer 2

select revenue.revenue_id, revenue.amount, bank.bank_amount, bank.bank_status 
from revenue
Inner join (select * 
              From bank
              Where bank_status = "Confirmed") bank
on bank.ref_no = revenue.revenue_id

Answer 3

对于左联接，必须使用第一个银行表，然后使用收入表。 因为在左连接中，即使没有匹配项，也将返回所有行。

因此，使用这样的查询。 选择Revenue.revenue_id，report.amount，bank.bank_amount，bank.bank_status 从银行 bank.ref_no =收入.revenue_id上​​的左加入收入 其中Revenue.status = 1，bank.bank_status =“已确认”