Update a table based on if two column values appear in another table on SQL Server 2008 R2

Question

I need to update a table column in SQL Server 2008 R2. The update depends on the two columns in another table.

Table1:

id1 (varchar(20)) id2 (varchar(20)) value (bit)  name_without_this_id1_id2
--------------------------------------------------------------------------
58                  669                null          null
188                 875                null          null
87                  30                 null          null

Table 2:

id0 (int) id1 (varchar(20)) id2 (varchar(20)) name(varchar(10))
---------------------------------------------------------------
1           58                  669                 ab
2           87                  30                  ac
3           58                  669                 ab

After update table 1, I can get:

id1 (varchar(20)) id2 (varchar(20)) value (bit)  name_without_this_id1_id2
--------------------------------------------------------------------------
58                  669                1          ac
188                 875                0          ab,ac
87                  30                 1          ab

About "name_without_this_id1_id2", if the combination of id1 and id2 are not available in table2's id1 and id2, the column "name"'s value in table2 needs to be added to the column "name_without_this_id1_id2" in table1. It means that id1 and id2 combination is not available for column "name" = "ac" in table2.

Answer 1

One way to check if a matching column exists in another table is to use EXISTS() function.

Below code should work

update table1 set value = 1
where exists( select 1 from table2 where table1.id1 = table2.id1 );

This function returns TRUE if subquery returns any rows.

Answer 2

You can use a join within update command to update all ids which exists in table2 (you can also use exists instead of join):

update table1
set value= 1
from table1 join table2 on table1.id1=table2.id1 and table1.id2=table2.id2

and finally set the null values to 0 (ids they are not in table2):

update table1
set value=0
where value is null