MySQL Development basic Series 7 process functions and other functions

I. Process functions

--Create a table to describeCREATE TABLESalary (UserIDINT, salaryDECIMAL(9,2));INSERT  intoSalaryVALUES(1, +),(2, -), (3, the),(4,4000),(5, the), (1,NULL);SELECT *  fromSalary

1. if (value,t,f) more than 2000 of the use of high, otherwise with low

SELECT IF (Salary> ,'high','low'   from Salary

2. Ifnull (VALUE1,VALUE2) The following statement replaces the null value 0

SELECT Ifnull (Salary,0 from salary;

3.case when ... To achieve high and low pay

SELECT  Case  whenSalary<= -  Then ' Low'  whenSalary>=2001  andSalary<=4000  Then'Middle' ELSE ' High'  END  fromSalary

Two. Other common functions

SELECT DATABASE() as 'Database name', VERSION () as 'Database Version',USER() as 'Current user name', Inet_aton ('192.168.1.1') as 'IP bytes', Inet_ntoa (3232235777) as 'IP byte to IP'

2. PASSWORD returns the encrypted character, typically used to set the password of the system user

SELECT PASSWORD ('123456')

3. MD5 (STR) encryption for general application data

SELECT MD5 ('123456');

MySQL Development basic Series 7 process functions and other functions