Mega Code Archive
Solution for the Mutating Tables Problem
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SQL>
SQL> -- create demo table
SQL> create table Employee(
2 ID VARCHAR2(4 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 /
1 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 /
1 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 /
1 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 /
1 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 /
1 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 /
1 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 /
1 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 /
1 row created.
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
8 rows selected.
SQL>
SQL> CREATE OR REPLACE PACKAGE EmployeeData AS
2 TYPE t_Salary IS TABLE OF employee.salary%TYPE INDEX BY BINARY_INTEGER;
3 TYPE t_IDs IS TABLE OF employee.ID%TYPE INDEX BY BINARY_INTEGER;
4
5 v_EmployeeSalary t_Salary;
6 v_EmployeeIDs t_IDs;
7 v_NumEntries BINARY_INTEGER := 0;
8 END EmployeeData;
9 /
Package created.
SQL>
SQL> CREATE OR REPLACE TRIGGER RLimitSalary
2 BEFORE INSERT OR UPDATE OF salary ON employee
3 FOR EACH ROW
4 BEGIN
5 /* Record the new data in EmployeeData. We don't make any
6 changes to employee, to avoid the ORA-4091 error. */
7 EmployeeData.v_NumEntries := EmployeeData.v_NumEntries + 1;
8 EmployeeData.v_EmployeeSalary(EmployeeData.v_NumEntries) := :new.salary;
9 EmployeeData.v_EmployeeIDs(EmployeeData.v_NumEntries) := :new.id;
10 END RLimitSalary;
11 /
Trigger created.
SQL>
SQL> CREATE OR REPLACE TRIGGER SLimitSalary
2 AFTER INSERT OR UPDATE OF salary ON employee
3 DECLARE
4 v_MaxEmployees CONSTANT NUMBER := 5;
5 v_CurrentEmployees NUMBER;
6 v_EmployeeID employee.ID%TYPE;
7 v_Salary employee.salary%TYPE;
8 BEGIN
9 /* Loop through each student inserted or updated, and verify
10 that we are still within the limit. */
11 FOR v_LoopIndex IN 1..EmployeeData.v_NumEntries LOOP
12 v_EmployeeID := EmployeeData.v_EmployeeIDs(v_LoopIndex);
13 v_Salary := EmployeeData.v_EmployeeSalary(v_LoopIndex);
14
15
16 SELECT COUNT(*)
17 INTO v_CurrentEmployees
18 FROM employee
19 WHERE salary = v_Salary;
20
21 -- If there isn't room, raise an error.
22 IF v_CurrentEmployees > v_MaxEmployees THEN
23 RAISE_APPLICATION_ERROR(-20000,
24 'Too much salary ' || v_Salary ||
25 ' because of employee ' || v_EmployeeID);
26 END IF;
27 END LOOP;
28
29 -- Reset the counter so the next execution will use new data.
30 EmployeeData.v_NumEntries := 0;
31 END SLimitSalary;
32 /
Trigger created.
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL>
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