SQL/MySQL/Procedure Function/Introduction
Содержание
Recursion
mysql>
Functions and procedures can call themselves.
mysql>
mysql> delimiter $$
mysql> CREATE FUNCTION factorial(n BIGINT) RETURNS BIGINT
-> BEGIN
-> IF n>=2 THEN
-> RETURN n * factorial(n-1);
-> ELSE
-> RETURN n;
-> END IF;
-> END$$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql>
mysql> SELECT factorial(3);
ERROR 1424 (HY000): Recursive stored functions and triggers are not allowed.
mysql>
mysql> drop function factorial;
Query OK, 0 rows affected (0.00 sec)
Use user-defined function in a select statement to deal with data in a table
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 (0.03 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", "O");
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","O");
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","U");
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","U");
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", "N");
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", "N");
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(8,"James", "Cat", "19960917", "20020415", 1232.78,"Vancouver", "N");
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 | O |
| 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | O |
| 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | U |
| 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | U |
| 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 | N |
| 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | N |
| 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | N |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.02 sec)
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql>
mysql> CREATE FUNCTION cust_status(in_status CHAR(1))
-> RETURNS VARCHAR(20)
-> BEGIN
-> DECLARE long_status VARCHAR(20);
->
-> IF in_status = "O" THEN
-> SET long_status="Overdue";
-> ELSEIF in_status = "U" THEN
-> SET long_status="Up to date";
-> ELSEIF in_status = "N" THEN
-> SET long_status="New";
-> END IF;
->
-> RETURN(long_status);
-> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> SELECT cust_status(description) as Status, count(*) as Count
-> FROM employee
-> GROUP BY description
-> ORDER BY cust_status(description);
+------------+-------+
| Status | Count |
+------------+-------+
| NULL | 1 |
| New | 3 |
| Overdue | 2 |
| Up to date | 2 |
+------------+-------+
4 rows in set, 1 warning (0.00 sec)
mysql>
mysql> drop function cust_status;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
Use user-defined function in order by clause
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 (0.03 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", "O");
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","O");
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","U");
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","U");
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", "N");
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", "N");
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", "N");
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 | O |
| 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | O |
| 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | U |
| 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | U |
| 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 | N |
| 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | N |
| 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | N |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql>
mysql> CREATE FUNCTION cust_status(in_status CHAR(1))
-> RETURNS VARCHAR(20)
-> BEGIN
-> DECLARE long_status VARCHAR(20);
->
-> IF in_status = "O" THEN
-> SET long_status="Overdue";
-> ELSEIF in_status = "U" THEN
-> SET long_status="Up to date";
-> ELSEIF in_status = "N" THEN
-> SET long_status="New";
-> END IF;
->
-> RETURN(long_status);
-> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> SELECT cust_status(description) as Status, count(*) as Count
-> FROM employee
-> GROUP BY description
-> ORDER BY cust_status(description);
+------------+-------+
| Status | Count |
+------------+-------+
| NULL | 1 |
| New | 3 |
| Overdue | 2 |
| Up to date | 2 |
+------------+-------+
4 rows in set, 1 warning (0.00 sec)
mysql>
mysql> drop function cust_status;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
Use user-defined function in where clause
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 (0.01 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 $$
mysql>
mysql> CREATE FUNCTION myFunction(in_rep_id INT)
-> RETURNS INT
-> READS SQL DATA
-> BEGIN
-> DECLARE customer_count INT;
->
-> SELECT COUNT(*)
-> INTO customer_count
-> FROM employee
-> WHERE id=in_rep_id;
->
-> RETURN(customer_count);
->
-> END$$
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 (0.01 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 (0.02 sec)
mysql>
Using user-defined function in a select statement
mysql> delimiter $$
mysql>
mysql> CREATE FUNCTION myFunction(
-> in_title VARCHAR(4),
-> in_gender CHAR(1),
-> in_firstname VARCHAR(20),
-> in_middle_initial CHAR(1),
-> in_surname VARCHAR(20))
->
-> RETURNS VARCHAR(60)
-> BEGIN
-> DECLARE l_title VARCHAR(4);
-> DECLARE l_name_string VARCHAR(60);
->
-> IF ISNULL(in_title) THEN
-> IF in_gender="M" THEN
-> SET l_title="Mr";
-> ELSE
-> SET l_title="Ms";
-> END IF;
-> END IF;
->
-> IF ISNULL(in_middle_initial) THEN
-> SET l_name_string=l_title||" "||in_firstname||" "||in_surname;
-> ELSE
-> SET l_name_string=l_title||" "||in_firstname||" "||
-> in_middle_initial||" "||in_surname;
-> END IF;
->
-> RETURN(l_name_string);
-> END$$
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, 2 warnings (0.00 sec)
mysql>
mysql>
mysql> select myFunction(null,"M","First","Middle","Last");
+----------------------------------------------+
| myFunction(null,"M","First","Middle","Last") |
+----------------------------------------------+
| 0 |
+----------------------------------------------+
1 row in set, 2 warnings (0.02 sec)
mysql>
mysql> drop function myFunction;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>