My MYSQL Study Notes (3) -- operators, mysql Study Notes

My MYSQL Study Notes (3) -- operators, mysql Study Notes

1. Security equals operator (<=>)

Select null <=> nullunion allselect null <=> 1 union ALLSELECT 1 <=> 0 UNION allSELECT NULL = NULL

Note that the difference between this operator and equal to (=) is that when both values are null, the execution result is as follows:

2. LEAST Operator
Purpose: obtain the minimum value among multiple parameter values.
Note: Do not use hybrid Data Types

SELECT least (2, 0), LEAST ('A', 'B', 'C', 'D'), least (10, 20, NULL)

Mixed use error

3. GREATEST Operator
Purpose: obtain the maximum value among multiple parameters.
Note: null Value

4. REGEXP Operator
Role: Regular Expression

SELECT 'ssky 'regexp '^ s', 'ssky 'regexp' y $ ', 'ssky 'regexp'. sky', 'ssky 'regexp '[s] *';