根据特定列值连接两个表

Question

I have two tables (Table 1 and Table 2) that I want to join them and create Table 3. The logic is the following:

Table 1

column1 | column2 | column3
user1 | ID1 | name1
user2 | ID2 | name2
user3 | ID3 | name3
user4 | ID4 | name4


Table 2

column1 | column2
user1 | ACT1
user1 | ACT1
user1 | ACT1
user1 | ACT1
user2 | ACT2
user3 | ACT3
user3 | ACT3
user3 | ACT3
user4 | ACT4

I want the joined table to be this way:

Table 3

column1 | column2 | column3
user1 | ACT1 | ID1
user1 | ACT1 | ID1
user1 | ACT1 | ID1
user1 | ACT1 | ID1
user2 | ACT2 | ID2
user3 | ACT3 | ID3
user3 | ACT3 | ID3
user3 | ACT3 | ID3
user4 | ACT4 | ID4

Basically, Table 3 is the same as Table 2. But, the corresponding ID for each user is fetched from Table1 and joined as a separate column. This process is repeated for all users.

Answer 1

You just need to use JOIN by column1 column from Table1 and Table2

select t2.*,t1.column2 as column3
from Table1 t1 
inner join Table2 t2 on t1.column1 = t2.column1  

[Results] :

| column1 | column2 | column3 |
|---------|---------|---------|
|   user1 |    ACT1 |     ID1 |
|   user1 |    ACT1 |     ID1 |
|   user1 |    ACT1 |     ID1 |
|   user1 |    ACT1 |     ID1 |
|   user2 |    ACT2 |     ID2 |
|   user3 |    ACT3 |     ID3 |
|   user3 |    ACT3 |     ID3 |
|   user3 |    ACT3 |     ID3 |
|   user4 |    ACT4 |     ID4 |

sqlfiddle

Answer 2

seems you need an inner join between table1 and table2 based on column1

select  t1.column1, t2.column2, t1.column2 as column3 
from table1 t1 
inner join table2 t2 on t1.column1 = t2.column1 

Answer 3

You can have that answer even more simple:

select  t1.column1, t2.column2, t1.column2 as column3 
from table1 as t1,  table2 as t2 
where t1.column1 = t2.column1