带有 ID 不匹配表的连接的 SQL 查询

Question

I have two tables.

Table 1
Id 
UpdateId
Name

Table 2
Table1ID
UpdateID
Address

Each time user update, system will insert record to table1 . But for table2 , system only insert record when there is update in address.

Sample data

Table 1
1,1,name1
1,2,name1
1,3,name1update
1,4,name1update
1,5,name1
1,6,name2

Table 2

1,1,address
1,4,addressupdate

I want to get the result as following

1,1,name1,address
1,2,name1,address
1,3,name1update,address
1,4,name1update,addressupdate
1,5,name1,addressupdate
1,6,name2,addressupdate 

How to make use of join condition to achieve as above?

Answer 1

you can use left join when you want to take all columns from left table t1 even though it doesn't match with the other table with column updateid on t2 table.

select t1.id,t1.updateid,t1.name,t2.address from table1 t1
left join table2 t2
on t2.updateid= t1.updateid

you can read more about joins here

Answer 2

You can use a correlated subquery. Here is standard syntax, but it can be easily adapted to any database:

select t1.*,
       (select t2.addressid
        from table2 t2
        where t2.table1id = t1.id and
              t2.updateid <= t1.updateid
        order by t2.updateid desc
        fetch first 1 row only
       ) as addressid
from table1 t1;