Question

I forget put delimiter directive, some semicolon and was using tsl syntax like [select variable = field] that is not valid in mysql.
Mysql error when you use tsl syntax is [not allowed to return a result set from a function] and dont help much.
@AndreKR point all of it to me, thanks.
Im using mysqlworkbench 5.2.30 CE.
The work function become:

delimiter //
CREATE FUNCTION nextval (seq_name varchar(100))  
  RETURNS bigint(20)  
    READS SQL DATA  
  NOT DETERMINISTIC  
    BEGIN  
     DECLARE workval bigint(20);  
     SELECT count(1) into workval  
        FROM tip_sequence  
        WHERE sequencename = seq_name;  
     IF workval <> 1 THEN  
        DELETE  
            FROM tip_sequence  
            WHERE sequencename = seq_name;  
        INSERT  
            INTO tip_sequence (sequencename, sequenceval, sequencestep)  
            VALUES (seq_name, 1, 1);  
     END IF;
     SELECT sequenceval into workval  
        FROM tip_sequence  
        WHERE sequencename = seq_name;  
     UPDATE tip_sequence  
        SET sequenceval = sequenceval + sequencestep  
        WHERE sequencename = seq_name;  
     RETURN workval;
    END//
delimiter ;

Answer 1

I don’t think the SELECT workval = count(1) FROM ... syntax is valid. I think what you mean is: SELECT count(1) INTO workval FROM ....