MySQL NOT operator

NOT operator

MySQL NOT operator reverses or negates the input.

This function is useful in -

• If you want to retrieve all records except those that meet a specific condition, NOT is invaluable.
• It allows you to negate the result of a condition.
• NOT makes queries more explicit. It clearly states that you want the opposite of a certain condition, which can help prevent misunderstandings or misinterpretations of your query.
• When you have complex conditions involving multiple logical operators like AND and OR, NOT can be crucial for achieving the desired outcome.
• NOT can be used to invert the logical meaning of a condition.
• In some scenarios, NOT can be used to conditionally insert or update records based on the absence of a specific condition.
• By using NOT judiciously, you can optimize your queries to efficiently retrieve the desired data.

Syntax:

NOT, !

The operator returns 1 if the operand is 0 and returns 0 if the operand is nonzero. It returns NULL if the operand is NOT NULL.

MySQL Version: 8.0

Example: MySQL NOT operator

In the following MySQL statement, NOT operator negates the input 10, it returns 0.

Code:

-- This SQL statement performs a logical NOT operation on the number 10
-- Explanation: The query evaluates a logical NOT operation on the number 10, returning the result of the operation.
SELECT !10;  -- The SELECT statement is used to evaluate the expression '!10' and return the result

Explanation:

• The SELECT statement is used to evaluate expressions and return the result.


• The ! operator is a logical NOT operator in MySQL.


• In the context of the expression !10:


• Any non-zero number is considered as TRUE.


• The logical NOT operation returns TRUE if the operand is FALSE, and FALSE if the operand is TRUE.


• Since 10 is a non-zero number, it is considered TRUE.


• !TRUE evaluates to FALSE, which is represented as 0 in MySQL.


• Therefore, the result of SELECT !10 is 0.

Output:

MySQL> SELECT ! 0;
+------+
| ! 10 |
+------+
|    0 | 
+------+
1 row in set (0.00 sec)

Example of MySQL NOT operator with zero input

In the following MySQL statement, NOT operator negates the input 0, it returns 1.

Code:

-- This SQL statement performs a logical NOT operation on the number 0
-- Explanation: The query evaluates a logical NOT operation on the number 0, returning the result of the operation.
SELECT ! 0;  -- The SELECT statement is used to evaluate the expression '!0' and return the result

Explanation:

• The SELECT statement is used to evaluate expressions and return the result.


• The ! operator is a logical NOT operator in MySQL.


• In the context of the expression !0:


• Zero (0) is considered as FALSE.


• The logical NOT operation returns TRUE if the operand is FALSE, and FALSE if the operand is TRUE.


• Since 0 is FALSE, !FALSE evaluates to TRUE, which is represented as 1 in MySQL.


• Therefore, the result of SELECT !0 is 1.

Example of MySQL NOT operator with zero input

In the following MySQL statement, NOT operator negates the input 0, it returns 1.

Output:

MySQL> SELECT ! 0;
+-----+
| ! 0 |
+-----+
|   1 | 
+-----+
1 row in set (0.00 sec)

Example of MySQL NOT operator with NULL

In the following MySQL statement, NOT operator negates the input NULL, it returns NULL.

Code:

-- This SQL statement performs a logical NOT operation on the value NULL
-- Explanation: The query evaluates a logical NOT operation on the value NULL, returning the result of the operation.
SELECT !NULL;  -- The SELECT statement is used to evaluate the expression '!NULL' and return the result

Explanation:

• The SELECT statement is used to evaluate expressions and return the result.


• The ! operator is a logical NOT operator in MySQL.


• In the context of the expression !NULL:


• NULL represents an unknown or undefined value in SQL.


• The logical NOT operation returns TRUE if the operand is FALSE, and FALSE if the operand is TRUE.


• However, if the operand is NULL, the result of the logical NOT operation is also NULL because the truth value is unknown.


• Therefore, the result of SELECT !NULL is NULL.

Output:

 MySQL> SELECT ! NULL;
+--------+
| ! NULL |
+--------+
|   NULL | 
+--------+
1 row in set (0.00 sec)
 

Example of MySQL NOT operator with non-zero input

In the following MySQL statement, NOT operator negates the input (10+10), it returns 0.

Code:

-- This SQL statement performs a logical NOT operation on the result of the expression (10 + 10)
-- Explanation: The query first evaluates the arithmetic expression (10 + 10), then performs a logical NOT operation on the result, returning the final result of the operation.
SELECT ! (10 + 10);  -- The SELECT statement is used to evaluate the expression '!(10 + 10)' and return the result

Explanation:

• The SELECT statement is used to evaluate expressions and return the result.


• The expression (10 + 10) is evaluated first.


• The arithmetic operation 10 + 10 results in 20.


• The ! operator is a logical NOT operator in MySQL.


• The result of (10 + 10) is 20.


• Any non-zero number is considered as TRUE.


• The logical NOT operation returns TRUE if the operand is FALSE, and FALSE if the operand is TRUE.


• Since 20 is a non-zero number, it is considered TRUE.


• !TRUE evaluates to FALSE, which is represented as 0 in MySQL.


• Therefore, the result of SELECT ! (10 + 10) is 0.

Output:

 MySQL> SELECT ! (10+10);
+-----------+
| ! (10+10) |
+-----------+
|         0 | 
+-----------+
1 row in set (0.00 sec)
 

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