MySQL Tutorial/Procedure Function/IF statement

Check version with if statement

   <source lang="sql">

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></source>

IF

   <source lang="sql">

IF search_condition THEN statement_list

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

END IF</source>

IF statement in a LOOP statement

   <source lang="sql">

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></source>

If statement with ELSEIF and ELSE

   <source lang="sql">

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></source>

Using OR in an IF statement

   <source lang="sql">

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></source>