如果两个现有列匹配，则SQL查询添加新列，并从另一列添加值

Question

表1列是（当前状态）

=======================================================
record_id |  ad_id | gender | gender_view | time_entry
=======================================================
1         |   1    |  male  |     45      | 1557072000
2         |   1    | female |     88      | 1557072000

表2列是（当前状态）

=====================
ad_id | submitted_by
=====================
1     |   1

在匹配表1和表2的ad_id之后，表1将具有新列的submitted_by 。 表1中提交的新列将从表2中获取submitted_by值。

表1列（预期状态）

====================================================================
record_id |  ad_id | gender | gender_view | time_entry | submitted_by 
====================================================================
1         |   1    |  male  |     45      | 1557072000 |   1
2         |   1    | female |     88      | 1557072000 |   1

Answer 1

ON T2.ad_id = T1.ad_id简单LEFT JOIN将返回您的预期结果：

SELECT T1.record_id,
       T1.ad_id,
       T1.gender,
       T1.gender_view,
       T1.time_entry
       COALESCE(T2.submitted_by, 0) submitted_by
FROM Table1 T1
LEFT JOIN Table2 T2 ON T2.ad_id = T1.ad_id

Answer 2

select t1.*,t2.submitted_by 
from table1 t1 
inner join table2 t2 on t1.ad_id = t2.ad_id