mysql 创建function

drop FUNCTION  IF EXISTS WORKNO;
create function WORKNO(projectno VARCHAR(5),workno VARCHAR(10) )
returns VARCHAR(100)

begin
declare seq integer;
declare timestr integer;
declare temp_seq integer;
declare number_return VARCHAR(100);

set timestr = DATE_FORMAT(now(),'%Y');

select sequence+1 INTO temp_seq from pe_number where  work_no = workno AND project_no=projectno;
UPDATE pe_number SET sequence = temp_seq WHERE work_no = workno AND project_no=projectno;

IF ROW_COUNT() = 0 THEN
SET seq = 1;
INSERT INTO pe_number(project_no,work_no,timestr,sequence) values(projectno,workno,timestr,seq);
end IF;

select CONCAT(project_no,work_no,timestr,LPAD(sequence,6,0)) INTO number_return from pe_number WHERE work_no = workno AND project_no=projectno;

return number_return;
end;