MINUS in Oracle SQL – PLSQL

A MINUS in Oracle SQL / PLSQL query is used to join or combine results from 2 or more SELECT statements, a MINUS returns only those rows which are found in the first SELECT statement but are not found in the second SELECT statement.

Also, each SELECT statement must have the same number of column(s)/field(s) with similar data-types for the MINUS to work.

Syntax for MINUS in Oracle SQL / PLSQL is:

SELECT column_name1
,column_name2
.
.
,column_nameN
FROM table_name(s)
MINUS
SELECT column_name1
,column_name2
.
.
,column_nameN
FROM table_name(s);

Suppose have a table named ‘employee’ in the database as shown below:

Also we have one more table ‘comm’ as shown below:

Let’s take an example to understand MINUS, suppose we write our SQL query using MINUS as:

SELECT employee_id
FROM employee
MINUS
SELECT emp_id
FROM comm;

The result of the above query will be:

Here we can see that the records for ‘employee_id’ = ‘102’,’103,’104’ and ‘105’ do not appear in the result set because they are present in both (‘employee’ and ‘comm’) tables.

The record for ‘employee_id’ = ‘101’ is present in employee table but is not present in ‘comm’ table and hence is placed in the result.

Suppose we change our SQL query for MINUS as:

SELECT emp_id
FROM comm
MINUS
SELECT employee_id
FROM employee;

The result of the above query will be:

Here we can see that the records for ‘employee_id’ = ‘102’,’103,’104’ and ‘105’ do not appear in the result set because they are present in both (‘employee’ and ‘comm’) tables.
The record for ‘employee_id’ = ‘101’ is present in employee table(second table) but is not present in ‘comm’ table (first table)and hence is not placed in the result.