relate tables to make a list (SQL)

Question

I have 3 tables with different columns except for one called "FileKey". I need a query that returns that field of the 3 tables as a list I think here is more easy to see

Please be patient, i'm new here :(

Answer 1

You can do this with a simple JOIN of the three tables ON the FileKey value.

SQL Inner-join with 3 tables?

Answer 2

you can use union like this:

Select FieldKey from TableA 
union 
Select FieldKey from TableB 
union
Select FieldKey from TableC

Using union it will not duplicate data if you have the same FieldKey in diferents tables.

if you want to duplicate data use union all like this:

Select FieldKey from TableA 
union all
Select FieldKey from TableB 
union all
Select FieldKey from TableC

check this link below to understand it better https://www.w3schools.com/sql/sql_union.asp

Answer 3

The best possible way to do this is by using UNION Operator. but if you don't want to use the UNION what you can do is to insert your all three table data to a temporary table and later on view it using a Select Statement.

DECLARE @TableA TABLE (ID INT);
DECLARE @TableB TABLE (ID INT);
DECLARE @TableC TABLE (ID INT);
DECLARE @Needed TABLE (ID INT);

INSERT INTO @TableA VALUES(53)
INSERT INTO @TableB VALUES(49)
INSERT INTO @TableC VALUES(34)

INSERT INTO @Needed (Id)
SELECT ID FROM @TableA

INSERT INTO @Needed (Id)
SELECT ID FROM @TableB

INSERT INTO @Needed (Id)
SELECT ID FROM @TableC


SELECT * FROM @Needed