MySQL Tutorial/Cursor/Declare
Creating Cursors
DECLARE...CURSOR, OPEN, FETCH, and CLOSE statements, as well as the HANDLER declaration are the statements for using cursors.
The statement to create the cursor is shown here:
DECLARE <cursor name> CURSOR FOR <SELECT statement>;
Declare a cursor
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 (0.01 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 $$
mysql>
mysql> CREATE PROCEDURE myProc (in_customer_id INT)
-> BEGIN
->
-> DECLARE v_id INT;
-> DECLARE v_name VARCHAR(30);
->
-> DECLARE c1 CURSOR FOR
-> SELECT id,first_name
-> FROM employee
-> WHERE id=in_customer_id;
->
->
-> END$$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql> call myProc(1);
Query OK, 0 rows affected (0.00 sec)
mysql> drop procedure myProc;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
Nested cursors
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", "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 $$
mysql> CREATE PROCEDURE myProc()
-> READS SQL DATA
-> BEGIN
->
-> DECLARE l_department_id INT;
-> DECLARE l_employee_id INT;
-> DECLARE l_emp_count INT DEFAULT 0 ;
-> DECLARE l_done INT DEFAULT 0;
->
-> DECLARE dept_csr cursor FOR
-> SELECT id FROM employee;
->
-> DECLARE emp_csr cursor FOR
-> SELECT id+1 FROM employee;
->
-> DECLARE CONTINUE HANDLER FOR NOT FOUND SET l_done=1;
->
-> OPEN dept_csr;
-> dept_loop: LOOP -- Loop through departments
-> FETCH dept_csr into l_department_id;
->
-> IF l_done=1 THEN
-> LEAVE dept_loop;
-> END IF;
->
-> OPEN emp_csr;
-> SET l_emp_count=0;
-> emp_loop: LOOP -- Loop through employee in dept.
-> FETCH emp_csr INTO l_employee_id;
->
-> IF l_done=1 THEN
-> LEAVE emp_loop;
-> END IF;
-> SET l_emp_count=l_emp_count+1;
-> END LOOP;
-> CLOSE emp_csr;
-> SET l_done=0;
->
-> SELECT CONCAT("Department ",l_department_id," has ",
-> l_emp_count," employees");
->
-> END LOOP dept_loop;
-> CLOSE dept_csr;
->
-> END$$
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> call myProc();
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 1 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 2 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 3 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 4 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 5 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 6 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 7 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
+------------------------------------------------------------------------------------+
| CONCAT("Department ",l_department_id," has ",
l_emp_count," employees") |
+------------------------------------------------------------------------------------+
| Department 8 has 8 employees |
+------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
Query OK, 0 rows affected (0.27 sec)
mysql> drop procedure myProc;
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>