----------------------------------Example
CREATE TABLE t1 (f1 varchar(1), f2 varchar(1), f3 varchar(1));
INSERT INTO t1 (f1, f2, f3) VALUES 
('a', 'b', 'c'), ('d', 'e', 'f'), ('g', 'h', 'i'), ('j', 'k', 'l');

DROP PROCEDURE IF EXISTS p_tst;

DELIMITER //

CREATE PROCEDURE p_tst(in_f1 varchar(1), in_f2 varchar(1), in_f3 varchar(1))
BEGIN
     DECLARE done INT DEFAULT 0;
     DECLARE v_ustat_criteria_lu_id MEDIUMINT UNSIGNED;
     DECLARE v_criteria_short_desc VARCHAR(30);
     DECLARE cur_ustat CURSOR FOR 
        SELECT * FROM t1;
     DECLARE continue handler for sqlstate '02000' set done = 1;

     DROP TABLE IF EXISTS t2;

     SET @s = 'CREATE  TABLE t2 AS
        SELECT ';

     IF in_f1 = 'Y' THEN
        SET @s = CONCAT(@s, 'f1, ');         
     END IF;

     IF in_f2 = 'Y' THEN
        SET @s = CONCAT(@s, 'f2, ');         
     END IF;
 
     IF in_f3 = 'Y' THEN
        SET @s = CONCAT(@s, 'f3, ');         
     END IF;
 
     SET @s = SUBSTRING(@s, 1, length(@s) -2);
     SET @s = CONCAT(@s, ' FROM t1');

     SELECT @s; 
     
     PREPARE stmt FROM @s;
     EXECUTE stmt;
     DEALLOCATE PREPARE stmt;
     SELECT @s;

     SELECT * FROM t2;
END
//

DELIMITER ;


-- After creating procedure, the first call to it always work correctly.
-- 1a) This call specifies that the table will be created with just the f1 column.

mysql> CALL p_tst('Y', 'N', 'N');
+-----------------------------------------------+
| @s                                            |
+-----------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1 FROM t1 |
+-----------------------------------------------+
1 row in set (0.00 sec)

+-----------------------------------------------+
| @s                                            |
+-----------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1 FROM t1 |
+-----------------------------------------------+
1 row in set (0.05 sec)

+------+
| f1   |
+------+
| a    |
| d    |
| g    |
| j    |
+------+
4 rows in set (0.05 sec)

Query OK, 0 rows affected (0.05 sec)


-- 1b) This call specifies that table t2 will contain same f1 column as above
-- plus additional columns f2 and f3.  This will return incorrect results.

mysql> CALL p_tst('Y', 'Y', 'Y');
+-------------------------------------------------------+
| @s                                                    |
+-------------------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1, f2, f3 FROM t1 |
+-------------------------------------------------------+
1 row in set (0.00 sec)

+-------------------------------------------------------+
| @s                                                    |
+-------------------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1, f2, f3 FROM t1 |
+-------------------------------------------------------+
1 row in set (0.02 sec)

+------+
| f1   |
+------+
| a    |
| d    |
| g    |
| j    |
+------+
4 rows in set (0.02 sec)

Query OK, 0 rows affected (0.02 sec)

-- Although the CREATE statement for t2 showed 3 columns, only 1 column 
-- was returned from SELECT * FROM t2, which is incorrect.

-- If I run the same SELECT statement at the command line, it works correctly.

mysql> SELECT * FROM t2;
+------+------+------+
| f1   | f2   | f3   |
+------+------+------+
| a    | b    | c    |
| d    | e    | f    |
| g    | h    | i    |
| j    | k    | l    |
+------+------+------+
4 rows in set (0.00 sec)

-- DROP:  Now I drop and recreate the procedure and start again. This is the only
-- way I've found to get the procedure to "reset" and return the correct results.

--  2a) This time I start with a call that specifies that the new table will have
--       all 3 columns.  This works correctly.  Note that this didn't work above.

mysql> CALL p_tst('Y', 'Y', 'Y');
+-------------------------------------------------------+
| @s                                                    |
+-------------------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1, f2, f3 FROM t1 |
+-------------------------------------------------------+
1 row in set (0.00 sec)

+-------------------------------------------------------+
| @s                                                    |
+-------------------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1, f2, f3 FROM t1 |
+-------------------------------------------------------+
1 row in set (0.03 sec)

+------+------+------+
| f1   | f2   | f3   |
+------+------+------+
| a    | b    | c    |
| d    | e    | f    |
| g    | h    | i    |
| j    | k    | l    |
+------+------+------+
4 rows in set (0.03 sec)

Query OK, 0 rows affected (0.03 sec)

-- 2b) But if I now specify that table t2 should have just one of these
--     columns, I get an error.

mysql> CALL p_tst('Y', 'N', 'N');
+-----------------------------------------------+
| @s                                            |
+-----------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1 FROM t1 |
+-----------------------------------------------+
1 row in set (0.00 sec)

+-----------------------------------------------+
| @s                                            |
+-----------------------------------------------+
| CREATE  TABLE t2 AS
        SELECT f1 FROM t1 |
+-----------------------------------------------+
1 row in set (0.03 sec)

ERROR 1054 (42S22): Unknown column '[db name].t2.f2' in 'field list'

-- But again, if I run the same query at the command line, I get
-- the correct results and no error.

mysql> SELECT * FROM t2;
+------+
| f1   |
+------+
| a    |
| d    |
| g    |
| j    |
+------+
4 rows in set (0.01 sec)

mysql> desc t2;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| f1    | varchar(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
1 row in set (0.01 sec)