Project Implementation for COSC 5050 Distributed Database Applications Lab3.
Distributed Database Applications COSC 5050 Week Three.
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Transcript of Distributed Database Applications COSC 5050 Week Three.
Jiangping WangDistributed Database Applications
Outline
Cursors and data retrieval
Procedures
Functions
Parameters
Sequences
Jiangping WangDistributed Database Applications
Cursors and Data Retrieval
PL/SQL integrates with the Oracle databaseSystem 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 cursorExplicit cursorCursor variable
Jiangping WangDistributed Database Applications
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;
Jiangping WangDistributed Database Applications
Cursorcreate 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;/
Jiangping WangDistributed Database Applications
Cursor Attributes
Page 468%FOUND
Status of fetch operationTrue if fetch succeeded
%NOTFOUNDOpposite of %FOUND
%ROWCOUNTNumber of records fetched
%ISOPENTrue if the cursor is open
cursor_name%attribute_name
Jiangping WangDistributed Database Applications
Referencing Variables in Cursor
Identifier precedence in a cursorQualifying variable with proc nameUsing standard naming conventions
create or replace PROCEDURE adjustIS 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;
Jiangping WangDistributed Database Applications
Implicit CursorUse 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;
Jiangping WangDistributed Database Applications
Implicit Cursor
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;/
Implicit SQL cursor attributes SQL%FOUNDSQL%NOTFOUNDSQL%ROWCOUNTSQL%ISOPEN
Error handlingWith exception
Jiangping WangDistributed Database Applications
Explicit CursorExplicitly defined in declaration sectionComplete 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%ROWTYPEIS SELECT * FROM employee WHERE department_id = 10;
Jiangping WangDistributed Database Applications
Explicit Cursor
OpenFetchCloseExplicit cursor attributes
cursor%FOUNDcursor%NOTFOUNDcursor%ROWCOUNTcursor%ISOPEN
Jiangping WangDistributed Database Applications
Explicit CursorDECLARE 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;/
Jiangping WangDistributed Database Applications
Explicit CursorDECLARE 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 WangDistributed Database Applications
Explicit CursorDECLARE 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;/
Jiangping WangDistributed Database Applications
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;/
Jiangping WangDistributed Database Applications
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;/
Jiangping WangDistributed Database Applications
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;
Jiangping WangDistributed Database Applications
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;
Jiangping WangDistributed Database Applications
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;
/
Jiangping WangDistributed Database Applications
Modular Code
PL/SQL offers the following structures that modularize your code in different ways
ProcedureFunctionTriggerPackage
Jiangping WangDistributed Database Applications
Procedure
Procedure is a module that performs one or more actionsCan be a standalone call, executable statement
Jiangping WangDistributed Database Applications
ProcedureCREATE OR REPLACEPROCEDURE get_happy (ename_in IN VARCHAR2)
Header
IS
hiredate DATE; Declarations
BEGIN
hiredate:= SYSDATE – 2; INSERT INTO employee (emp_name, hiredate)
VALUES (ename_in, hiredate);
Code Body
EXCEPTION * optional *
WHEN DUP_VAL_IN_INDEX THEN DBMS_OUTPUT.PUT_LINE (‘Cannot insert.’);
Exception block* optional *
END get_happy;
Jiangping WangDistributed Database Applications
Procedureprocedure 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;
Jiangping WangDistributed Database Applications
Procedureprocedure 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;
Jiangping WangDistributed Database Applications
Procedure
Calling a procedureProcedure is called as an executable PL/SQL statementCalled in a blockMust end with (;)
beginapply_discount( new_company_id, 0.15 );display_store_summary;display_store_summary();
end;
Jiangping WangDistributed Database Applications
Function
Function is a module that returns a valueFunction can exist only as part of an executable statementFunction has a datatype
Jiangping WangDistributed Database Applications
FunctionCREATE OR REPLACEFUNCTION soft_pillow (type_in IN VARCHAR2)
RETURN BOOLEAN
Header
IS
CURSOR pillow_cur (type_in pillow.pillow_type%TYPE) ISSELECT softnessFROM pillowWHERE pillow_type = type-in;
Pillow_rec pillow_cur%ROWTYPE;
Declarations
BEGIN
OPEN pillow_cur(type_in);FETCH pillow_cur INTO Pillow_rec;CLOSE pillow_cur;RETURN Pillow_rec.softness;
Code Body
EXCEPTION * optional *
Exception block* optional *
END soft_pillow;
Jiangping WangDistributed Database Applications
Function
Defining function
create or replace function favorite_nickname( name_in in varchar2) return varchar2isbeginEnd;
Calling function
declarenickname varchar2(100) := favorite_nickname(‘Nic’);
Jiangping WangDistributed Database Applications
Functioncreate or replace function get_department( ssn_in in employee.ssn%type) return department.dept_name%typeis 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;/
Jiangping WangDistributed Database Applications
Parameter
Be used to pass information back and forthParameter declaration must be unconstrained
DECLARE company_name varchar2(60);
PROCEDURE display_company( company_name IN varchar2) IS …
Jiangping WangDistributed Database Applications
Parameter ModeIN mode: Read-only
Is the default modeValue cannot be changedCan have default valuePassed by reference
OUT mode: Write-onlyHas no value until the endNo default valueActual parameter must be a variablePassed by value
IN OUT mode: Read-writeCannot have default valueMust be a variablePassed by value
Jiangping WangDistributed Database Applications
Parametercreate 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;/
Jiangping Wang
Parameter
Distributed Database Applications
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')ISBEGIN 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;/
Jiangping WangDistributed Database Applications
Oracle SequencesIndependent object in the database
Not a data typeNot tied to a table or a columnCan be used anywhere a value is expected
Generate a numeric value that can be assigned to any column in any tableThe table attribute to which you assigned a value based on a sequence can be edited and modifiedCan be created and deleted anytime
Jiangping WangDistributed Database Applications
Oracle SequencesCREATE 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;
Jiangping WangDistributed Database Applications
Oracle SequencesINSERT 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);
Jiangping WangDistributed Database Applications
Oracle SequencesOnce a sequence value is used (through NEXTVAL), it cannot be used againIf SQL statement rolls back, the sequence value does not roll backA 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 generatedA sequence has one purpose: assign unique numbers to stuff
Do not expect a sequence to return gap free values
Jiangping WangDistributed Database Applications
HomeworkCreate 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