Question

as title states. here’s the function

DELIMITER //
CREATE FUNCTION GetCreateValue( table_name CHAR(64), id_field CHAR(64), name_field CHAR(64), name_value CHAR(64) )
RETURNS INTEGER
BEGIN
    DECLARE ret INTEGER;
    SELECT count(*) INTO ret FROM table_name WHERE name_field = name_value;
    IF ret < 1 THEN
        INSERT INTO table_name SET name_field = name_value;
        SELECT id_field INTO ret FROM table_name WHERE name_field = name_value;
    ELSE    
        SELECT id_field INTO ret FROM table_name WHERE name_field = name_value;
    END IF;
    RETURN ret;
END//
DELIMITER ;

when I run something like

SELECT GetCreateValue('table1', 'ID', 'name', '123456');

I get an error that the table “table_name” does’t exist. Clearly the parameter wasnt passed. Why?

Answer 1

SET @qry = 
   CONCAT(
     'SELECT count(*) INTO ret FROM ', table_name, 
      ' WHERE ', name_field, 
      ' = ?');

PREPARE stmt1 FROM @qry;
SET @v = name_value;
EXECUTE stmt1 USING @v;
DEALLOCATE PREPARE stmt1;