Distributed Database
Applications
COSC 5050
Week Three
Outline
Cursors and data retrieval
Procedures
Functions
Parameters
Sequences
Distributed Database Applications
Jiangping Wang
Cursors and Data Retrieval
PL/SQL integrates with the Oracle database
System Global Area (SGA)
Private working area for SQL statement
Cursor
To query data from the database and make
that data available within PL/SQL programs
Implicit cursor
Explicit cursor
Cursor variable
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Jiangping Wang
Cursor
Cursor is a pointer into a virtual table in
the database
CURSOR employee_cur IS
SELECT fname, lname FROM employee;
OPEN employee_cur;
FETCH employee_cur INTO employee_rec;
CLOSE employee_cur;
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Jiangping Wang
Cursor Fetch Operation
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Cursor
create or replace procedure cursor_employee
is
CURSOR employee_cur IS
SELECT fname, lname
FROM employee
WHERE ssn = '600000001';
employee_rec employee_cur%rowtype;
begin
OPEN employee_cur;
FETCH employee_cur INTO employee_rec;
dbms_output.put_line(
employee_rec.fname || ' ' ||employee_rec.lname);
CLOSE employee_cur;
end;
/
Distributed Database Applications
Jiangping Wang
Cursor Attributes
Page 468
cursor_name%attribute_name
%FOUND
Status of fetch operation
True if fetch succeeded
%NOTFOUND
Opposite of %FOUND
%ROWCOUNT
Number of records fetched
%ISOPEN
True if the cursor is open
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Referencing Variables in Cursor
Identifier precedence in a cursor
Qualifying variable with proc name
Using standard naming conventions
create or replace PROCEDURE adjust
IS
l_code NUMBER := 1000;
CURSOR double_code_cur
IS
SELECT code + l_code as adjusted
FROM employee
WHERE dept_num = 2;
employee_rec double_code_cur%rowtype;
begin
OPEN double_code_cur;
FETCH double_code_cur INTO employee_rec;
dbms_output.put_line(employee_rec.adjusted);
CLOSE double_code_cur;
END;
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Jiangping Wang
Implicit Cursor
Use SELECT INTO
DECLARE
l_department department.dept_name%TYPE;
BEGIN
SELECT dept_name INTO l_department
FROM department
WHERE dept_num = 1;
DBMS_OUTPUT.PUT_LINE(l_department);
END;
DECLARE
l_department department%ROWTYPE;
BEGIN
SELECT * INTO l_department
FROM department
WHERE dept_num = 1;
DBMS_OUTPUT.PUT_LINE(l_department.dept_name);
END;
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Jiangping Wang
Implicit Cursor
Error handling
With exception
Implicit SQL cursor attributes
SQL%FOUND
SQL%NOTFOUND
SQL%ROWCOUNT
SQL%ISOPEN
DECLARE
l_department department%ROWTYPE;
BEGIN
SELECT * INTO l_department
FROM department
WHERE dept_num = 3;
DBMS_OUTPUT.PUT_LINE(l_department.dept_name);
EXCEPTION
WHEN NO_DATA_FOUND
THEN
DBMS_OUTPUT.PUT_LINE('No data!');
WHEN TOO_MANY_ROWS
THEN
DBMS_OUTPUT.PUT_LINE('Too many rows');
END;
/
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Jiangping Wang
Explicit Cursor
Explicitly defined in declaration section
Complete control over open, fetch, close
CURSOR company_cur IS
SELECT company_id FROM company;
CURSOR name_cur (company_id_in IN NUMBER)
IS
SELECT name FROM company
WHERE company_id = company_id_in;
CURSOR emp_cur RETURN employee%ROWTYPE
IS
SELECT * FROM employee
WHERE department_id = 10;
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Explicit Cursor
Open
Fetch
Close
Explicit cursor attributes
cursor%FOUND
cursor%NOTFOUND
cursor%ROWCOUNT
cursor%ISOPEN
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Explicit Cursor
DECLARE
CURSOR c1 IS
SELECT fname, lname, code, code*1.1 new_code
FROM employee;
rec c1%ROWTYPE;
BEGIN
OPEN c1;
LOOP
FETCH c1 INTO rec;
EXIT WHEN c1%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(
rec.fname || ' ' || rec.lname || ' ' ||
rec.code || ' ' || rec.new_code);
END LOOP;
CLOSE c1;
END;
/
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Jiangping Wang
Explicit Cursor
DECLARE
l_dept_id NUMBER := 1;
CURSOR name_cur (dept_id_in IN NUMBER)
IS
SELECT dept_name, lname
FROM department inner join employee
on department.dept_mgr_ssn = employee.ssn
WHERE department.dept_num = dept_id_in;
name_rec name_cur%ROWTYPE;
BEGIN
OPEN name_cur(l_dept_id);
LOOP
FETCH name_cur INTO name_rec;
EXIT WHEN name_cur%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(
name_rec.dept_name || ' ' || name_rec.lname);
END LOOP;
CLOSE name_cur;
END;
/
Jiangping Wang
Distributed Database Applications
Explicit Cursor
DECLARE
CURSOR emp_cur RETURN employee%rowtype
IS
SELECT * FROM employee WHERE dept_num = 15;
emp_rec emp_cur%ROWTYPE;
BEGIN
OPEN emp_cur;
LOOP
FETCH emp_cur INTO emp_rec;
EXIT WHEN emp_cur%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(emp_cur%rowcount || ': ' ||
emp_rec.fname || ' ' || emp_rec.lname);
END LOOP;
CLOSE emp_cur;
END;
/
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Jiangping Wang
Cursor Variable
Cursor variable points to or references
an underlying cursor
DECLARE
TYPE employee_curtype IS REF CURSOR
RETURN employee%ROWTYPE;
employee_curvar employee_curtype;
employee_rec employee%ROWTYPE;
BEGIN
OPEN employee_curvar FOR
SELECT * FROM employee;
FETCH employee_curvar INTO employee_rec;
CLOSE employee_curvar;
dbms_output.put_line(employee_rec.fname);
END;
/
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Jiangping Wang
Cursor Loop
Cursor with simple loop
DECLARE
CURSOR name_cur IS
SELECT lname, fname
FROM employee WHERE ssn like '8%';
name_rec name_cur%ROWTYPE;
BEGIN
OPEN name_cur;
LOOP
FETCH name_cur INTO name_rec;
EXIT WHEN name_cur%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(
name_rec.fname || ' ' || name_rec.lname);
END LOOP;
CLOSE name_cur;
END;
/
Distributed Database Applications
Jiangping Wang
Cursor Loop
Cursor with simple loop
DECLARE
CURSOR occupancy_cur IS
SELECT pet_id, room_number
FROM occupancy
WHERE occupied_dt = TRUNC(SYSDATE);
occupancy_rec occupancy_cur%ROWTYPE;
BEGIN
OPEN occupancy_cur;
LOOP
FETCH occupancy_cur INTO occupancy_rec;
EXIT WHEN occupancy_cur%NOTFOUND;
update_bill
(occupancy_rec.pet_id, occupancy_rec.room_number);
END LOOP;
CLOSE occupancy_cur;
END;
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Cursor FOR Loop
Cursor For loop
DECLARE
CURSOR occupancy_cur IS
SELECT pet_id, room_number
FROM occupancy
WHERE occupied_dt = TRUNC(SYSDATE);
BEGIN
FOR occupancy_rec IN occupancy_cur
LOOP
update_bill
(occupancy_rec.pet_id, occupancy_rec.room_number);
END LOOP;
END;
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Jiangping Wang
Cursor FOR Loop
Cursor FOR loop
DECLARE
CURSOR name_cur IS
SELECT lname, fname
FROM employee WHERE ssn like '8%';
BEGIN
FOR name_rec IN name_cur
LOOP
DBMS_OUTPUT.PUT_LINE(
name_rec.fname || ' ' || name_rec.lname);
END LOOP;
END;
/
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Jiangping Wang
Modular Code
PL/SQL offers the following structures
that modularize your code in different
ways
Procedure
Function
Trigger
Package
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Procedure
Procedure is a module that performs
one or more actions
Can be a standalone call, executable
statement
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Procedure
CREATE OR REPLACE
PROCEDURE get_happy (ename_in IN VARCHAR2)
 Header
IS
 Declarations
hiredate DATE;
BEGIN
hiredate:= SYSDATE – 2;
INSERT INTO employee (emp_name, hiredate)
VALUES (ename_in, hiredate);
EXCEPTION
 Code Body
* optional *
WHEN DUP_VAL_IN_INDEX THEN
DBMS_OUTPUT.PUT_LINE (‘Cannot insert.’);
 Exception block
* optional *
END get_happy;
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Jiangping Wang
Procedure
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Jiangping Wang
Procedure
procedure Add_employee
(ssn
in
varchar2
, fname
in
varchar2
, lname
in
varchar2
, dept_num
in
number
, code
in
number
, sup_ssn
in
varchar2)
is
begin
insert into employee values
(ssn, fname, lname, dept_num, code, sup_ssn);
end;
Distributed Database Applications
Jiangping Wang
Procedure
procedure delete_employee (tgt_ssn in varchar2)
is
cursor dept_mgr_cur (tst_ssn varchar2)
is
select dept_mgr_ssn
from department
where dept_mgr_ssn = tst_ssn;
dept_mgr_cur_ssn varchar2(9);
begin
open dept_mgr_cur(tgt_ssn);
fetch dept_mgr_cur into dept_mgr_cur_ssn;
if (dept_mgr_cur%found) then
update department set dept_mgr_ssn = NULL
where dept_mgr_ssn = tgt_ssn;
end if;
delete from employee where ssn = tgt_ssn;
close dept_mgr_cur;
end;
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Jiangping Wang
Procedure
Calling a procedure
Procedure is called as an executable
PL/SQL statement
Called in a block
Must end with (;)
begin
apply_discount( new_company_id, 0.15 );
display_store_summary;
display_store_summary();
end;
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Function
Function is a module that returns a
value
Function can exist only as part of an
executable statement
Function has a datatype
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Jiangping Wang
Function
CREATE OR REPLACE
FUNCTION soft_pillow (type_in IN VARCHAR2)
RETURN BOOLEAN
 Header
IS
CURSOR pillow_cur (type_in pillow.pillow_type%TYPE) IS
SELECT softness
FROM pillow
WHERE pillow_type = type-in;
Pillow_rec pillow_cur%ROWTYPE;
 Declarations
BEGIN
 Code Body
OPEN pillow_cur(type_in);
FETCH pillow_cur INTO Pillow_rec;
CLOSE pillow_cur;
RETURN Pillow_rec.softness;
EXCEPTION
* optional *
 Exception block
* optional *
END soft_pillow;
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Jiangping Wang
Function
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Jiangping Wang
Function
Defining function
create or replace function favorite_nickname(
name_in in varchar2) return varchar2
is
begin
End;
Calling function
declare
nickname varchar2(100) :=
favorite_nickname(‘Nic’);
Distributed Database Applications
Jiangping Wang
Function
create or replace function get_department(
ssn_in in employee.ssn%type)
return department.dept_name%type
is
l_dept_name department.dept_name%type;
begin
select dept_name into l_dept_name
from department inner join employee
on employee.dept_num = department.dept_num
where ssn = ssn_in;
dbms_output.put_line('department name: ' || l_dept_name);
return l_dept_name;
exception
when no_data_found then
dbms_output.put_line(
'no such employee or not in any department!');
return null;
end;
/
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Jiangping Wang
Parameter
Be used to pass information back and
forth
Parameter declaration must be
unconstrained
DECLARE
company_name varchar2(60);
PROCEDURE display_company(
company_name IN varchar2)
IS …
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Jiangping Wang
Parameter Mode
IN mode: Read-only
Is the default mode
Value cannot be changed
Can have default value
Passed by reference
OUT mode: Write-only
Has no value until the end
No default value
Actual parameter must be a variable
Passed by value
IN OUT mode: Read-write
Cannot have default value
Must be a variable
Passed by value
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Jiangping Wang
Parameter
create or replace procedure delete_employee (
tgt_ssn_in in varchar2, removed_name_out out varchar2)
is
cursor dept_mgr_cur (tst_ssn varchar2)
is
select dept_mgr_ssn from department
where dept_mgr_ssn = tst_ssn;
dept_mgr_cur_ssn varchar2(9);
begin
open dept_mgr_cur(tgt_ssn_in);
fetch dept_mgr_cur into dept_mgr_cur_ssn;
if (dept_mgr_cur%found) then
update department set dept_mgr_ssn = NULL
where dept_mgr_ssn = tgt_ssn_in;
end if;
select lname into removed_name_out from employee
where ssn = tgt_ssn_in;
delete from employee where ssn = tgt_ssn_in;
close dept_mgr_cur;
end;
/
Distributed Database Applications
Jiangping Wang
Parameter
create or replace PROCEDURE combine_and_format_names
(first_name_inout IN OUT VARCHAR2,
last_name_inout IN OUT VARCHAR2,
full_name_out OUT VARCHAR2,
name_format_in IN VARCHAR2 := 'LAST, FIRST')
IS
BEGIN
first_name_inout := UPPER (first_name_inout);
last_name_inout := UPPER (last_name_inout);
IF name_format_in = 'LAST, FIRST'
THEN
full_name_out := last_name_inout || ', ' || first_name_inout;
ELSIF name_format_in = 'FIRST LAST'
THEN
full_name_out := first_name_inout || ' ' || last_name_inout;
END IF;
END;
/
Distributed Database Applications
Jiangping Wang
Oracle Sequences
Independent object in the database
Not a data type
Not tied to a table or a column
Can be used anywhere a value is expected
Generate a numeric value that can be
assigned to any column in any table
The table attribute to which you assigned a
value based on a sequence can be edited and
modified
Can be created and deleted anytime
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Jiangping Wang
Oracle Sequences
CREATE SEQUENCE NAME [START WITH N] [INCREMENT
BY N] [CACHE | NOCACHE]
CREATE SEQUENCE CUS_CODE_SEQ START WITH 20010
NOCACHE;
CREATE SEQUENCE INV_NUMBER_SEQ START WITH 4010
NOCACHE;
SELECT * FROM USER_SEQUENCES;
DROP SEQUENCE CUS_CODE_SEQ;
DROP SEQUENCE INV_NUMBER_SEQ;
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Oracle Sequences
INSERT INTO CUSTOMER VALUES
(CUS_CODE_SEQ.NEXTVAL, ‘CONNERY’, ‘SEAN’, NULL,
‘615’, ‘898-2007’, 0.00);
INSERT INTO INVOICE VALUES
(INV_NUMBER_SEQ.NEXTVAL, 20010, SYSDATE);
INSERT INTO LINE VALUES
(INV_NUMBER_SEQ.CURRVAL, 1, ‘13-Q2/P2’, 1,
14.99);
INSERT INTO LINE VALUES
(INV_NUMBER_SEQ.CURRVAL, 2, ‘23109-HB’, 1,
9.95);
Distributed Database Applications
Jiangping Wang
Oracle Sequences
Once a sequence value is used (through
NEXTVAL), it cannot be used again
If SQL statement rolls back, the sequence
value does not roll back
A sequence is not associated with a table
A sequence can be used to generate unique
values for more than one tables
Dropping a sequence does not delete the
values generated
A sequence has one purpose: assign unique
numbers to stuff
Do not expect a sequence to return gap free
values
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Homework
Create a function that returns the next
available customer ID.
Create a stored procedure that accepts
customer data as input arguments, adds a
new customer record to the customer table.
Create a stored procedure that accepts a
numeric amount as an input argument that
will be used as a filter threshold and prints
a listing of customer information.
Lab activities
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