Creating a Function to deal with business rules : Function « Function Procedure Packages « Oracle PL/SQL Tutorial

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Oracle PL/SQL Tutorial » Function Procedure Packages » Function 
27. 1. 6. Creating a Function to deal with business rules
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /

Table created.

SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ('01','Jason',    'Martin',  to_date('19960725','YYYYMMDD'), to_date('20060725','YYYYMMDD'), 1234.56'Toronto',  'Programmer')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('02','Alison',   'Mathews', to_date('19760321','YYYYMMDD'), to_date('19860221','YYYYMMDD'), 6661.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('03','James',    'Smith',   to_date('19781212','YYYYMMDD'), to_date('19900315','YYYYMMDD'), 6544.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('04','Celia',    'Rice',    to_date('19821024','YYYYMMDD'), to_date('19990421','YYYYMMDD'), 2344.78'Vancouver','Manager')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('05','Robert',   'Black',   to_date('19840115','YYYYMMDD'), to_date('19980808','YYYYMMDD'), 2334.78'Vancouver','Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('06','Linda',    'Green',   to_date('19870730','YYYYMMDD'), to_date('19960104','YYYYMMDD'), 4322.78,'New York',  'Tester')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('07','David',    'Larry',   to_date('19901231','YYYYMMDD'), to_date('19980212','YYYYMMDD'), 7897.78,'New York',  'Manager')
  3  /

row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('08','James',    'Cat',     to_date('19960917','YYYYMMDD'), to_date('20020415','YYYYMMDD'), 1232.78,'Vancouver', 'Tester')
  3  /

row created.

SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select from Employee
  2  /

ID   FIRST_NAME           LAST_NAME            START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- -------------------- -------------------- --------- --------- ---------- ---------- ---------------
01   Jason                Martin               25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison               Mathews              21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James                Smith                12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia                Rice                 24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert               Black                15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda                Green                30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David                Larry                31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James                Cat                  17-SEP-96 15-APR-02    1232.78 Vancouver  Tester

rows selected.

SQL>
SQL>
SQL>
SQL> CREATE OR REPLACE FUNCTION AlmostFull (
  2    p_first_name employee.first_name%TYPE,
  3    p_last_name  employee.last_name%TYPE)
  4    RETURN BOOLEAN IS
  5
  6    v_CurrentEmployees NUMBER;
  7    v_MaxEmployees     NUMBER;
  8    v_ReturnValue     BOOLEAN;
  9    v_FullPercent     CONSTANT NUMBER := 90;
 10  BEGIN
 11    SELECT salary
 12      INTO v_CurrentEmployees
 13      FROM employee
 14      WHERE first_name = p_first_name
 15      AND last_name = p_last_name;
 16
 17    SELECT max(salary)
 18      INTO v_MaxEmployees
 19      FROM employee;
 20
 21
 22    IF (v_CurrentEmployees / v_MaxEmployees * 100> v_FullPercent THEN
 23      v_ReturnValue := TRUE;
 24    ELSE
 25      v_ReturnValue := FALSE;
 26    END IF;
 27
 28    RETURN v_ReturnValue;
 29  END AlmostFull;
 30  /

SP2-0806: Function created with compilation warnings

SQL>
SQL>
SQL> DECLARE
  2    CURSOR c_employee IS
  3      SELECT first_name, last_name
  4        FROM employee;
  5  BEGIN
  6    FOR v_employee IN c_employee LOOP
  7      IF AlmostFull(v_employee.first_name, v_employee.last_nameTHEN
  8        DBMS_OUTPUT.put_line(v_employee.first_name || ' ' || v_employee.last_name || ' is almost full!');
  9      END IF;
 10    END LOOP;
 11  END;
 12  /
David Larry is almost full!

PL/SQL procedure successfully completed.

SQL>
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /

Table dropped.

SQL>
27. 1. Function
27. 1. 1. Functions
27. 1. 2. Describe a user-defined function
27. 1. 3. create or replace FUNCTION iifn(boolean_expression in BOOLEAN,true_number IN NUMBER,false_number IN NUMBER)
27. 1. 4. Storing PL/SQL function in the Database
27. 1. 5. Create a simple function
27. 1. 6. Creating a Function to deal with business rules
27. 1. 7. CREATE OR REPLACE a function
27. 1. 8. Calling a Function
27. 1. 9. Calling a Function for a table
27. 1. 10. Function without parameters
27. 1. 11. Exit a function
27. 1. 12. How to Call a Function from PL/SQL With or Without Parameters
27. 1. 13. Local Subprograms
27. 1. 14. Dependency Example
27. 1. 15. The FullName Function
27. 1. 16. PLW-05005: function NO_RETURN returns without value at line 21
27. 1. 17. Use function to check passwords
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