Advanced Database Management System - Tutorials and Notes: EXCEPT or MINUS Set operator in SQL

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Monday, 15 June 2020

EXCEPT or MINUS Set operator in SQL





MINUS (EXCEPT) Operator
Let us use the following tables for explaining the concept of the set operators;
Regno
Name
Phone
10BS0123
Madhavan
9965235412
10BC0234
Jerry
8569326541
11BM0023
Malar
9658236542
11BC0003
Kumar
9653268954
 Table 2 - S_Cricket (Students registered for Cricket)
Regno
Name
Phone
10MS0434
Noel
9856452314
10MS0012
Kumar
9653268954
11MC0070
Ramkumar
9965235412
11BC0003
Kumar
9653268954
 Table 2 - S_Basketball (Students registered for Basketball)


MINUS is used to filter records that are unique to first expression only. That is, the system will find all the common records of expression 1 and 2, remove the common records, and display only records from the result of expression 1. For example, consider the query given below, which gives the students details who have registered only for cricket.

(SELECT Name, Phone FROM S_Cricket) MINUS (SELECT Name, Phone FROM S_Basketball);
----- Query 1

The result of this query will be;



Regno
Name
Phone
10BS0123
Madhavan
9965235412
10BC0234
Jerry
8569326541
11BM0023
Malar
9658236542
 
 Table 3 shows the result generated from Query 1. Here, except the common record, i.e, except ('11BC0003', 'Kumar', 9653268954), the result will contain all the other records of result of expression 1.


Support for SQL Set Operator MINUS (EXCEPT) in Various DBMSs:

MINUS (EXCEPT) operator in MySQL

MySQL does not support MINUS (EXCEPT). It can be achieved through other ways using the keywords NOT IN or NOT EXISTS. Query 1 is rewritten using the keyword NOT IN as follows to achieve exception in MySQL.

SELECT Name, Phone FROM S_Cricket WHERE (Name, Phone) NOT IN (SELECT Name, Phone FROM S_Basketball);

----- Query 2

 

MINUS (EXCEPT) operator in Oracle

Oracle supports MINUS operator as discussed above. The above example (Query 1) can be treated as example for Oracle MINUS operator.

MINUS (EXCEPT) operator in DB2

DB2 supports EXCEPT operator. Above examples can be treated as examples for DB2 with MINUS replaced as EXCEPT. An example is shown in Query 3;
(SELECT Name, Phone FROM S_Cricket) EXCEPT (SELECT Name, Phone FROM S_Basketball);
----- Query 3

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