What does! in mysql mean?

The ! symbol in MySQL represents the negation operator, which can be used to: negate Boolean expressions, turning TRUE into FALSE and FALSE into TRUE. Negates a number, but does not change the sign of the number, but negates its boolean value.

The meaning of ! in MySQL

In the MySQL database, ! The symbol represents the negation operator, which can be used to negate Boolean expressions.

Specific usage

• Negative Boolean expression: ! Operator can be used to evaluate a Boolean expression Negate the formula. For example, if x is TRUE, then !x is FALSE.
• Negate numbers: The - symbol can also be used to negate numbers, but this is different from the ! operator. The - operator inverts a number and produces a negative value, while the ! operator simply inverts the Boolean value of a number.

Examples

Here are some examples of using the ! operator:

• SELECT * FROM table WHERE name != 'John';: Select all rows in the table where the name column is not equal to "John".
• SET x = !x;: Negate the value of variable x.
• IF (!x) { ... };: If x is FALSE, the statements in the block are executed.

Note

• ! operators have higher precedence than relational operators, so you need to be careful when using them.
• ! The operator cannot be used alone, it must be used with a Boolean expression or number.

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