delimiter // CREATE FUNCTION DBROAM.GET_FORMVALUE ( str in varchar2 ) return number is cursor_name integer; ret integer; val number(12,4); begin val := -1; begin cursor_name := dbms_sql.open_cursor; dbms_sql.parse(cursor_name, 'select '||str||' from dual', dbms_sql.v7); dbms_sql.define_column (cursor_name, 1, val); ret := dbms_sql.execute(cursor_name); if dbms_sql.fetch_rows (cursor_name)<>0 then dbms_sql.column_value (cursor_name, 1, val); end if; dbms_sql.close_cursor(cursor_name); exception when others then dbms_sql.close_cursor(cursor_name); end; return val; end; // delimiter ;改写成mysql可以运行的

好的，根据你提供的Oracle函数代码，我将其转换为MySQL函数代码如下：

delimiter //
CREATE FUNCTION GET_FORMVALUE (str VARCHAR(100)) RETURNS DECIMAL(12,4)
BEGIN
    DECLARE cursor_name INTEGER;
    DECLARE ret INTEGER;
    DECLARE val DECIMAL(12,4);
    
    SET val = -1;
    SET cursor_name = 0;
    SET ret = 0;
    
    BEGIN
        SET cursor_name = (SELECT @@session.pseudo_thread_id);
        PREPARE my_query FROM CONCAT('SELECT ', str, ' FROM dual');
        EXECUTE my_query;
        DEALLOCATE PREPARE my_query;
        
        IF cursor_name > 0 THEN
            SET ret = 1;
        END IF;
        
        IF ret = 1 THEN
            FETCH cursor_name INTO val;
        END IF;
        
        CLOSE cursor_name;
    END;
    
    RETURN val;
END;//
delimiter ;

请注意，MySQL中不存在`dbms_sql`包，所以我使用了动态SQL来编写查询语句。此外，由于MySQL不支持`%TYPE`语法，因此我将返回值类型设置为DECIMAL(12,4)。如果你需要返回不同的数据类型，可以根据需要进行更改。