MySQL - built-in functions

1. Date function

•  get year month day

•  get hours

• get timestamp 

• add date to date

 

•  Subtract time from date

 

• Calculate the number of days between two dates

 

Create a table to record birthdays

 

 

 Create a table to record strings and record times

2. String functions

•  Get the character set of a column in the record table

•  As shown in the figure

•  Find the number of bytes occupied by the student's name in the student table

 

3. Mathematical functions

• absolute value

 

•  Improvement arrangement

•  adjust down

•  Two decimal places (rounding)

•  generate random numbers

 

4. Other functions

• user() query the current user

•  md5(str) performs md5 digest on a string, and gets a 32-bit string after digest

•  show the database we are using

•  ifnull(val1, val2) If val1 is null, return val2, otherwise return the value of val1