SQL查询如果两个现有列匹配，则添加新列，并从另一列添加值

Question

table 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

table 2 列是(当前状态(

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

匹配表1和表2的 AD_ID ，表1将具有新的列提交。表1中的新列提交的_BY将从表2中获取提交的_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

带有ON T2.ad_id = T1.ad_id的简单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