循环结构 while
create procedure name()
  begin
    while 条件 do
      SQL语句
    end while;
  end$


create procedure aa6()
    begin
      declare number int default 0;
      while number < 5 do
        select number;
        set number = number + 1;
        end while;
    end$


mysql> create procedure aa6()
    ->     begin
    ->       declare number int default 0;
    ->       while number < 5 do
    ->         select number;
    ->         set number = number + 1;
    ->         end while;
    ->     end$
Query OK, 0 rows affected (0.00 sec)

mysql> call aa6$
+--------+
| number |
+--------+
|      0 |
+--------+
1 row in set (0.00 sec)

+--------+
| number |
+--------+
|      1 |
+--------+
1 row in set (0.01 sec)

+--------+
| number |
+--------+
|      2 |
+--------+
1 row in set (0.01 sec)

+--------+
| number |
+--------+
|      3 |
+--------+
1 row in set (0.01 sec)

+--------+
| number |
+--------+
|      4 |
+--------+
1 row in set (0.02 sec)

Query OK, 0 rows affected (0.02 sec)