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SQL NOT EQUAL Operator - GeeksforGeeks

The SQL NOT EQUAL operator is a comparison operator used to check if two expressions are not equal to each other. It helps filter out records that match certain conditions, making it a valuable tool in SQL queries.

In this article, We will explore the SQL NOT EQUAL operator, including its syntax, use cases, and examples for both beginners and advanced users.

NOT EQUAL Operator in SQL is used to compare two values and return if they are not equal. This operator returns boolean values. If given expressions are equal, the operator returns false otherwise true. If any one expression is NULL, it will return NULL.

It performs type conversion when expressions are of different data types, for example, 5!= "Five".

We use the NOT EQUAL operator to display our table without some exceptional values. For example, Let's, consider a table 'Students'. For this table, we have, "id", "name", and "marks" as its columns. Now we want to display all those rows that have marks not equal to "100". In this kind of situation, the NOT EQUAL operator can be used.

Note: <> and != perform the same operation i.e. check inequality. The only difference between <> and != is that <> follows 
the ISO standard but != does not. So it is recommended to use <> for NOT EQUAL Operator.

Syntax:

The SQL NOT EQUAL Operator syntax is:

SELECT * FROM table_name
WHERE column_name != value;

Let's look at some examples of the NOT EQUAL Operator in SQL, and understand its working.

First, we will create a demo SQL database and table on which we will use the NOT EQUAL operator.

Query:

CREATE TABLE geeksforgeeks(
  user_id varchar(100) PRIMARY KEY,
  name varchar(100),
  contest_score int,
  rank int,
  coding_streak int
 );
INSERT INTO geeksforgeeks(user_id,name,contest_score,rank,coding_streak)
VALUES('vish3001','Vishu',100,01,150);
INSERT INTO geeksforgeeks(user_id,name,contest_score,rank,coding_streak)
VALUES('neeraj119','Neeraj',99,02,125);
INSERT INTO geeksforgeeks(user_id,name,contest_score,rank,coding_streak)
VALUES('ayush105','Aayush',98,03,110);
INSERT INTO geeksforgeeks(user_id,name,contest_score,rank,coding_streak)
VALUES('sumit85','Sumit',99,02,100);
INSERT INTO geeksforgeeks(user_id,name,contest_score,rank,coding_streak)
VALUES('harsh05','Harsh',98,03,95);

Output:

In this example, we will display all those rows which do not have a name equal to 'Harsh'. We will use NOT EQUAL with WHERE clause in this case.

Query:

SELECT * 
FROM students
WHERE name != 'Harsh';

In the above image, we can see we have all those rows displayed which do not have their name equal to 'Harsh'.

Note: The NOT EQUAL comparison is case-sensitive for strings. Meaning "geeks" and "GEEKS" are two different strings for NOT EQUAL operator.

In this example, we will display all those rows which do not have their contest score as 98 and rank as 3 and the coding streak should be greater than or equal to 100. Using AND or OR operator you can use the SQL NOT operator for multiple values.

Query:

SELECT * FROM geeksforgeeks
WHERE contest_score != 98 AND rank != 3
AND coding_streak >= 100;

In the above image, we can observe that all those rows are displayed which have followed all three conditions.

In this example, we will display all those ranks with their count that do not have their contest score as 100 using GROUP BY clause. 

Query:

SELECT rank, COUNT(*) as count_score
FROM geeksforgeeks
WHERE contest_score <> 100
GROUP BY rank;

In the above image, we can see ranks 2, and 3 have a count of 2 and, 2 respectively.

Also Read: EQUAL Operators in SQL

• SQL NOT EQUAL Operator is a comparison operator denoted as != or <>. It returns boolean values i.e. True or False.
• It returns False when the compared expressions are equal otherwise it returns True.
• We use this operator with the WHERE clause.
• We can use this operator for integers and strings-based logical reasoning. It is case-sensitive for string comparisons.
• We can put multiple conditions using the AND or OR operator.

The SQL NOT EQUAL operator is a powerful comparison operator that helps filter records where values do not match a given condition. It can be used with various data types (strings, numbers, dates) and combined with other logical operators for complex querying. By understanding and implementing the NOT EQUAL operator in SQL, we can write more efficient and accurate queries to exclude specific data from your result set.

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