MySQL functions and stored procedures

function

/ * 
Function: The function will only return a value, not allowed to return a result set. It stressed that the return value of the function, it does not allow the situation to return multiple values, even query. Separated by commas into a plurality of parameters. 
Note: In the function, if the same query table field with the parameter name, you need to prefix the field name with an alias, or when there are problems in identifying the program does not complain, but a problem with the query results. 
* / 
Drop  function  IF  EXISTS Myf;
 Create  function Myf (REGION_CODE VARCHAR ( 10 )) Returns  int 
the begin  
    DECLARE C int ; - definition of variables, requires the query into a variable C INTO XXX SELECT; 
    SELECT PM10 from data_region_month T WHERE T. REGION_CODE = REGION_CODE limit . 1  INTO C;
     return c;
end;
select myf('411025');
select myf(region_code) from data_region_month;

 

Stored Procedures