SQLite Union All Operator

The SQLite UNION ALL operator is used to combine the result of two or more SELECT statement without ignoring the duplicate rows.

In SQLite UNION ALL, the resultant table also includes the duplicate values. Otherwise, the same rule applies as Union.

Syntax:

snippet

SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions]
UNION ALL
SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions];

Example:

We have two tables "STUDENT" and "DEPARTMENT".

The "STUDENT" table is having the following data:

The "DEPARTMENT" table is having the following data:

Example1: Return Single Field

This simple example returns only one field from multiple SELECT statements where the both fields have same data type.

Let's take the above two tables "STUDENT" and "DEPARTMENT" and select id from both table to make UNION ALL.

snippet

SELECT ID FROM STUDENT
UNION ALL 
SELECT ID FROM DEPARTMENT;

Output:

Example2: UNION ALL with Inner and Outer Join

Let's take the above two tables "STUDENT" and "DEPARTMENT" and make an inner join and outer join according to the below conditions along with UNION ALL Clause:

snippet

SELECT EMP_ID, NAME, DEPT FROM STUDENT INNER JOIN DEPARTMENT
ON STUDENT.ID = DEPARTMENT.EMP_ID
UNION ALL
SELECT EMP_ID, NAME, DEPT FROM STUDENT LEFT OUTER JOIN DEPARTMENT
ON STUDENT.ID = DEPARTMENT.EMP_ID;

Output: