MINUSPLSQL

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:

Employee_Id	Employee_Name	Salary	Department	Commission
101	Emp A	10000	Sales	10
102	Emp B	20000	IT	20
103	Emp C	28000	IT	20
104	Emp D	30000	Support
105	Emp E	32000	Sales	10

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

Emp_Id	Commission_Percent
102	20
103	20
104
105	10
106	15
107	25

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:

Employee_Id

101

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:

Emp_Id

106

107

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.