MySQL Tutorial/Procedure Function/Function Returning
Содержание
Check function parameter and return value
<source lang="sql">
mysql> mysql> delimiter $$ mysql> mysql> CREATE FUNCTION myFunction(in_status CHAR(1))
-> RETURNS VARCHAR(20) -> BEGIN -> IF in_status = "O" THEN -> RETURN("Overdue"); -> ELSEIF in_status = "U" THEN -> RETURN("Up to date"); -> ELSEIF in_status = "N" THEN -> RETURN("New"); -> END IF; -> END$$
Query OK, 0 rows affected (0.00 sec) mysql> mysql> delimiter ; mysql> mysql> select myFunction("O"); +-----------------+ | myFunction("O") | +-----------------+ | Overdue | +-----------------+ 1 row in set (0.00 sec) mysql> mysql> select myFunction("U"); +-----------------+ | myFunction("U") | +-----------------+ | Up to date | +-----------------+ 1 row in set (0.00 sec) mysql> mysql> select myFunction("N"); +-----------------+ | myFunction("N") | +-----------------+ | New | +-----------------+ 1 row in set (0.00 sec) mysql> mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.00 sec) mysql> mysql></source>
Returning Decimal from the function
<source lang="sql">
mysql> mysql> DELIMITER // mysql> mysql> CREATE FUNCTION myFunction (rush_ship INT(10)) RETURNS DECIMAL(10,2)
-> BEGIN -> -> DECLARE rush_shipping_cost DECIMAL(10,2); -> -> CASE rush_ship -> WHEN 1 THEN -> SET rush_shipping_cost = 20.00; -> WHEN 2 THEN -> SET rush_shipping_cost = 15.00; -> WHEN 3 THEN -> SET rush_shipping_cost = 10.00; -> ELSE -> SET rush_shipping_cost = 0.00; -> END CASE; -> -> RETURN rush_shipping_cost; -> -> END -> //
Query OK, 0 rows affected (0.00 sec) mysql> DELIMITER ; mysql> mysql> select myFunction(1); +---------------+ | myFunction(1) | +---------------+ | 20.00 | +---------------+ 1 row in set (0.00 sec) mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.02 sec)</source>
Return integer value from a function
<source lang="sql">
mysql> mysql> 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 (0.00 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 (0.00 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 (0.02 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 $$ mysql> CREATE FUNCTION myFunction (in_dob datetime) returns int
-> NO SQL -> BEGIN -> DECLARE l_age INT; -> IF DATE_FORMAT(NOW(),"00-%m-%d") >= DATE_FORMAT(in_dob,"00-%m-%d") THEN -> SET l_age=DATE_FORMAT(NOW(),"%Y")-DATE_FORMAT(in_dob,"%Y"); -> ELSE -> SET l_age=DATE_FORMAT(NOW(),"%Y")-DATE_FORMAT(in_dob,"%Y")-1; -> END IF; -> RETURN(l_age); -> -> END$$
Query OK, 0 rows affected (0.00 sec) mysql> delimiter ; mysql> mysql> select myFunction(start_date) from employee; +------------------------+ | myFunction(start_date) | +------------------------+ | 10 | | 31 | | 28 | | 24 | | 23 | | 19 | | 16 | | 10 | +------------------------+ 8 rows in set (0.00 sec) mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.00 sec) mysql> mysql> mysql> mysql> mysql> drop table Employee; Query OK, 0 rows affected (0.00 sec) mysql> mysql></source>
Return NUMERIC(8,2) from a function
<source lang="sql">
mysql> mysql> mysql> delimiter $$ mysql> CREATE FUNCTION myFunction(normal_price NUMERIC(8,2))
-> RETURNS NUMERIC(8,2) -> BEGIN -> -> DECLARE discount_price NUMERIC(8,2); -> -> IF (normal_price>500) THEN -> SET discount_price=normal_price*.8; -> ELSEIF (normal_price>100) THEN -> SET discount_price=normal_price*.9; -> ELSE -> SET discount_price=normal_price; -> END IF; -> RETURN(discount_price); -> END$$
Query OK, 0 rows affected (0.00 sec) mysql> delimiter ; mysql> mysql> select myFunction(123.123); +---------------------+ | myFunction(123.123) | +---------------------+ | 110.81 | +---------------------+ 1 row in set, 2 warnings (0.02 sec) mysql> mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.00 sec) mysql> mysql></source>
Return value from a function
<source lang="sql">
mysql> mysql> delimiter $$ mysql> mysql> CREATE FUNCTION myFunction(
-> in_title VARCHAR(4), -> in_gender CHAR(1), -> in_firstname VARCHAR(20), -> in_middle_initial CHAR(1), -> in_surname VARCHAR(20)) -> -> RETURNS VARCHAR(60) -> BEGIN -> DECLARE l_title VARCHAR(4); -> DECLARE l_name_string VARCHAR(60); -> -> IF ISNULL(in_title) THEN -> IF in_gender="M" THEN -> SET l_title="Mr"; -> ELSE -> SET l_title="Ms"; -> END IF; -> END IF; -> -> IF ISNULL(in_middle_initial) THEN -> SET l_name_string=CONCAT(l_title," ",in_firstname," ",in_surname); -> ELSE -> SET l_name_string=CONCAT(l_title," ",in_firstname," ", -> in_middle_initial," ",in_surname); -> END IF; -> -> RETURN(l_name_string); -> END$$
Query OK, 0 rows affected (0.00 sec) mysql> mysql> delimiter ; mysql> mysql> select myFunction("Mrs","M","First","Middle","Last"); +-----------------------------------------------+ | myFunction("Mrs","M","First","Middle","Last") | +-----------------------------------------------+ | NULL | +-----------------------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> mysql> mysql> select myFunction(null,"M","First","Middle","Last"); +----------------------------------------------+ | myFunction(null,"M","First","Middle","Last") | +----------------------------------------------+ | Mr First M Last | +----------------------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.00 sec) mysql> mysql></source>
Using the returning value from a user-defined function in order by clause
<source lang="sql">
mysql> 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 (0.02 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 (0.00 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 (0.00 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 $$ mysql> mysql> CREATE FUNCTION myFunction(in_rep_id INT)
-> RETURNS INT -> READS SQL DATA -> BEGIN -> DECLARE customer_count INT; -> -> SELECT COUNT(*) -> INTO customer_count -> FROM employee -> WHERE id=in_rep_id; -> -> RETURN(customer_count); -> -> END$$
Query OK, 0 rows affected (0.00 sec) mysql> mysql> delimiter ; mysql> mysql> SELECT id,myFunction(id)
-> FROM employee -> WHERE myFunction(id)>0 -> ORDER BY myFunction(id) desc;
+------+----------------+ | id | myFunction(id) | +------+----------------+ | 1 | 1 | | 2 | 1 | | 3 | 1 | | 4 | 1 | | 5 | 1 | | 6 | 1 | | 7 | 1 | | 8 | 1 | +------+----------------+ 8 rows in set (0.02 sec) mysql> mysql> drop function myFunction; Query OK, 0 rows affected (0.01 sec) mysql> mysql> mysql> mysql> mysql> drop table Employee; Query OK, 0 rows affected (0.00 sec) mysql> mysql></source>