SQL function-a statement error is always prompted when you create a function in mysql.

I saved a tree structure in the department table of the database and looked up all parent departments when the sub-departments are known. the written function is as follows & quot; CREATEFUNCTIONqueryAllDept (@ currdeptidvarchar (50 )) returnsvarchar (200) BEGINdeclare @ allnamevarchar (200) DEFAULT & #39; & #39; declare @ tempnamevarchar (200) DEFAULT & #39; & #39 ;; declare @ tempparidvar mysqlsql function loop query

I have a tree structure in the department table of the database. when we know the sub-department, we can look up all parent departments. the written functions are as follows:

CREATE FUNCTION queryAllDept(@currdeptid varchar(50))returns varchar(200)BEGIN    declare @allname varchar(200) DEFAULT '';    declare @tempname varchar(200) DEFAULT '';    declare @tempparid varchar(200) DEFAULT '';    select @allname=`name`,@tempparid=parid from ym_dept where id=@currdeptid;    while(@tempparid <> '0') do        select @tempname=`name`,@tempparid=parid from ym_dept where id=@tempparid;        set @allname=CONCAT(@tempname,',',@allname);    end while;    RETURN @allname;END

Error message:
[Err] 1064-You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@ currdeptid varchar (50 ))
Returns varchar (200)
BEGIN
Declare @ allname varchar 'at line 1

Where is the problem?