MySQL advanced development

Built in functions

Concept

In development, it is called ‘ Method ’ Put a set of logical statements in the method body Method name of external exposure

effect

1 Hidden code implementation details

2 Increase the weight of the code

Calling method

select  Function name 
 To operate on a table, you need to add a table 
select  Function name ( Parameters ) from  surface 

concerns

Function name

The functionality

classification

One line function for example concat() length() etc.

Group function for example sum() count()

Other functions now()

One line function

Each data row in the table can be processed ,

length() You can see how many bytes a character takes

select length('abc');
select length(' Ah ah ');