MySQL Tutorial/Procedure Function/IF statement

Check version with if statement

mysql>
mysql> delimiter $$
mysql>
mysql> CREATE PROCEDURE myProc()
    -> BEGIN
    ->
    ->     IF (INSTR(version(),"alpha")>0) THEN
    ->               SELECT "Alpha release of MySQL";
    ->     ELSEIF (INSTR(version(),"beta")>0) THEN
    ->               SELECT "Beta release of MySQL";
    ->     ELSE
    ->               SELECT "Production release of MySQL";
    ->     END IF;
    ->
    ->
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> call myProc();
+-----------------------------+
| Production release of MySQL |
+-----------------------------+
| Production release of MySQL |
+-----------------------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop procedure myProc;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>

IF

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

IF statement in a LOOP statement

mysql>
mysql> delimiter $$
mysql>
mysql> CREATE PROCEDURE myProc()
    -> BEGIN
    ->
    ->     DECLARE i int;
    ->     SET i=0;
    ->     loop1: REPEAT
    ->          SET i=i+1;
    ->          IF MOD(i,2)<>0 THEN /*Even number - try again*/
    ->             SELECT CONCAT(i," is an odd number");
    ->          END IF;
    ->     UNTIL i >= 10
    ->     END REPEAT;
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql> call myProc();
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 1 is an odd number            |
+-------------------------------+
1 row in set (0.00 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 3 is an odd number            |
+-------------------------------+
1 row in set (0.33 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 5 is an odd number            |
+-------------------------------+
1 row in set (0.33 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 7 is an odd number            |
+-------------------------------+
1 row in set (0.34 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 9 is an odd number            |
+-------------------------------+
1 row in set (0.34 sec)
Query OK, 0 rows affected (0.34 sec)
mysql> drop procedure myProc;
Query OK, 0 rows affected (0.00 sec)
mysql>

If statement with ELSEIF and ELSE

mysql>
mysql> delimiter $$
mysql> CREATE PROCEDURE myProc(normal_price NUMERIC(8,2),OUT discount_price NUMERIC(8,2))
    -> NO SQL
    -> BEGIN
    ->     IF (normal_price>500) THEN
    ->        SET discount_price=normal_price*.8;
    ->     ELSEIF (normal_price>100) THEN
    ->        SET discount_price=normal_price*.9;
    ->
    ->     ELSE
    ->        SET discount_price=normal_price;
    ->     END IF;
    ->     select discount_price;
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql> set @p = 600;
Query OK, 0 rows affected (0.00 sec)
mysql> set @dp = 0;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> call myProc(@p, @dp);
+----------------+
| discount_price |
+----------------+
|         480.00 |
+----------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> select @dp;
+--------+
| @dp    |
+--------+
| 480.00 |
+--------+
1 row in set (0.00 sec)
mysql> drop procedure myProc;
Query OK, 0 rows affected (0.00 sec)
mysql>

Using OR in an IF statement

mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->              values (1,"Jason",    "Martin",  "19960725",  "20060725", 1234.56, "Toronto",  "Programmer");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(2,"Alison",   "Mathews",  "19760321", "19860221", 6661.78, "Vancouver","Tester");
Query OK, 1 row affected (0.01 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(3,"James",    "Smith",    "19781212", "19900315", 6544.78, "Vancouver","Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(4,"Celia",    "Rice",     "19821024", "19990421", 2344.78, "Vancouver","Manager");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(5,"Robert",   "Black",    "19840115", "19980808", 2334.78, "Vancouver","Tester");
Query OK, 1 row affected (0.02 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(6,"Linda",    "Green",    "19870730", "19960104", 4322.78,"New York",  "Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(7,"David",    "Larry",    "19901231", "19980212", 7897.78,"New York",  "Manager");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
    ->               values(8,"James",    "Cat",     "19960917",  "20020415", 1232.78,"Vancouver", "Tester");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql> CREATE PROCEDURE myProc(in_employee_id INT, in_new_salary NUMERIC(8,2))
    -> DETERMINISTIC
    -> BEGIN
    ->      IF in_new_salary <5000 OR in_new_salary > 500000 THEN
    ->           SELECT "Illegal salary; salary must be between $5,000 and $500,000";
    ->      ELSE
    ->           UPDATE employee SET salary=in_new_salary
    ->                  WHERE id=in_employee_id;
    ->      END IF;
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql> call myProc(1, 6000);
Query OK, 1 row affected (0.02 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 6000.00 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql> call myProc(1,4000);
+------------------------------------------------------------+
| Illegal salary; salary must be between $5,000 and $500,000 |
+------------------------------------------------------------+
| Illegal salary; salary must be between $5,000 and $500,000 |
+------------------------------------------------------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> DROP PROCEDURE myProc;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql>
mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>