MySQL Tutorial/Procedure Function/Introduction — различия между версиями

Текущая версия на 09:53, 26 мая 2010

Содержание

1 Recursion
2 Use user-defined function in a select statement to deal with data in a table
3 Use user-defined function in order by clause
4 Use user-defined function in where clause
5 Using user-defined function in a select statement

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

A function can be used directly from within a SELECT, INSERT, or UPDATE statement.

The result of that function is either saved in the table or returned with the output.

Stored procedures may not return any results.

A stored function always returns a single value.

A stored procedure is executed with an explicit statement: the CALL command.

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>

MySQL Tutorial/Procedure Function/Introduction — различия между версиями

Текущая версия на 09:53, 26 мая 2010

Содержание

Recursion

Use user-defined function in a select statement to deal with data in a table

Use user-defined function in order by clause

Use user-defined function in where clause

Using user-defined function in a select statement

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Версия 13:44, 26 мая 2010 (просмотреть исходный код) (обсуждение) ← Предыдущая правка	Текущая версия на 09:53, 26 мая 2010 (просмотреть исходный код) Admin (обсуждение \| вклад) м (1 версия)
(нет различий)