Combining output of two or more select statement

Question

How to combine output of two or more SELECT statements, I have multiple tables which are having some data that I need to fetch them so I write multiple SELECT query. Now I want to combine result of the queries so what do I need to do ? I want the output to be:

t1.qty,t2.qty,t3.qty 

Answer 1

One option would be:

SELECT (SELECT SUM(qty) FROM Table1 WHERE ...),
       (SELECT SUM(qty) FROM Table2 WHERE ...),
       (SELECT SUM(qty) FROM Table3 WHERE ...)

Another would be joining, provided that there is a link:

SELECT * 
FROM   (SELECT ID,SUM(qty) FROM Table1 GROUP BY ID) T1
       JOIN (SELECT ID,SUM(qty) FROM Table2 GROUP BY ID) T2
           ON T1.ID = T2.ID
       JOIN (SELECT ID,SUM(qty) FROM Table3 GROUP BY ID) T3
           ON T1.ID = T3.ID

The above options would be to display results in one row.

You may need union to combine rows:

SELECT qty FROM Table1
UNION
SELECT qty FROM Table2
UNION
SELECT qty FROM Table3

Much more options if you define more specific needs

Answer 2

Why not create a statement that will fetch them all at once?

SELECT tableA.data1, tableB.data2 FROM tableA, tableB WHERE <condition here>