A tutorial on how MySQL uses loop loop statements to implement storage

There are three standard loops in the statements of the MySQL stored procedure: The while loop, the loop loop, and the repeat loop. There is also a non-standard way of cycling: GOTO, but this cycle is best not to use, it is easy to cause confusion in the program, here is a good introduction.

Today we'll take a look at the loop loop.

Mysql>
mysql> delimiter $$
Mysql>
mysql> CREATE PROCEDURE myProc ()
   -& Gt BEGIN
   
   ->     DECLARE i int;
    ->     SET i=0;
   ->     loop1:loop
   ->           SET i=i+1;
   ->          IF i>=10 then          /*last number-exit loop*/
   ->                LEAVE Loop1;
   ->          ELSEIF MOD (i,2) =0 THEN/*even Number-try again*/
   ->                Iterate Loop1;
   ->          End IF;
   
   ->          SELECT CONCAT (i, "is a odd number");
   
   ->     end LOOP LOOP1
    
   
   -> end$$
Query OK, 0 rows affected (0.02 sec)

Mysql>
Mysql> delimiter;
Mysql> call MyProc ();
+-------------------------------+
| CONCAT (i, "is a odd number") |
+-------------------------------+
| 1 is a odd number |
+-------------------------------+
1 row in Set (0.00 sec)

+-------------------------------+
| CONCAT (i, "is a odd number") |
+-------------------------------+
| 3 is a odd number |
+-------------------------------+
1 row in Set (0.00 sec)

+-------------------------------+
| CONCAT (i, "is a odd number") |
+-------------------------------+
| 5 is a odd number |
+-------------------------------+
1 row in Set (0.00 sec)

+-------------------------------+
| CONCAT (i, "is a odd number") |
+-------------------------------+
| 7 is a odd number |
+-------------------------------+
1 row in Set (0.01 sec)

+-------------------------------+
| CONCAT (i, "is a odd number") |
+-------------------------------+
| 9 is a odd number |
+-------------------------------+
1 row in Set (0.01 sec)

Query OK, 0 rows affected (0.01 sec)

Mysql> drop procedure MyProc;
Query OK, 0 rows Affected (0.00 sec)

Mysql>