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".

Sqlite Union all operator 1

The "STUDENT" table is having the following data:

Sqlite Union all operator 2

The "DEPARTMENT" table is having the following data:

Sqlite Union all operator 3

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:

Sqlite Union all operator 4

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:

Sqlite Union all operator 5
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