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Module 9: Referential Integrity and Triggers

After completing this module, you will be able to:

Describe the concept and benefits of referential integrity.

Explain the concepts behind relationships that occur amongtables.

Use the INSERT and UPDATE statements to make changes to

a table that has references to other tables.

Describe the access rights you need to create and replacetriggers.

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Referential Integrity

Reasons to implement RI

Data integrity and consistency

Increases development productivityusers dont have to code SQL

statements to enforce referential constraints

Optimized performance Teradata chooses the most efficient method

to enforce the referential constraints

User applications may rely on Referential Integrity for their functionality

Relationships among tables based on the definition of:

A primary key - referenced column

A foreign key - referencing column

Referenced columns must be defined as:

Unique columns

Not Null columns

Prevents database corruption when performing INSERT, UPDATEs, and

DELETEs.

A row cannot exist with a non-null value for a referencing column if an equalvalue does not exist in a referenced column.

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Referential Model

Employee Dept Emp_Mgr Job Last First Salary

Number Number Number Code Name Name Amount

PK FK FK FK

100001 1001 ? 3000 DeBosse Ibee 200000.00

100797 1048 100791 3017 Myers Ruth 41000.00

100002 1001 100001 3001 Smith Steve 110000.00

100471 1028 100442 3017 Roberts Rich 40000.00

100389 1023 100381 3018 Ball Jason 64000.00

Employee

Job Job

Code Description

PK

3000 President

3001 Senior Mgmt

3017 Analyst L2

3018 Analyst L1

3045 Assembler L4

Job

Dept Dept Dept_Mgr Budget

Number Name Number Amount

PK FK

1048 Design SW 100791 1000000.00

1050 Design Services 100811 1000000.00

1028 Engineering SW 100441 3000000.00

1023 Engineering Disk 100381 2000000.00

1001 Leadership Team 10000

1 5000000.00

Department

Employee Area Phone

Number Code Number Extension

PK

FK

100001 937 5100001 1001

100001 937 4100001 1001

100389 858 4852815 815

100797 770 9082445 445

100797 310 5554512 ?

Employee_Phone

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Implementing Referential Integrity

Two different approaches to establishing RI and populating tables.

First Approach (recommended):

1. Create the tables and define the Primary Keys.

2. Populate the tables.

3. Create the Foreign Key references.

Second approach:

1. Create the tables and define the Primary Keys.

2. Create the Foreign Key references.

3. Populate the tables.

From previous example: The Department table has a nullable foreign key reference to the Employee table.

The Job table references no other table.

The Employee table has foreign key reference to the Department and Job tables.

Compress is not allowed on either the referencing or referenced columns. The

data types must be the same.

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Circular References

Employee DeptNumber Number

PK1 FK2

: :

100341 1022

Employee

Dept Dept Dept_MgrNumber Name Number

PK2 FK1

: : :

1022 Engineering CPU 100341

Department

INSERT INTO Employee (Employee_Number, Dept_Number, . . .)

VALUES (100341, NULL, . . .);

INSERT INTO Department (Dept_Number, Dept_Name, Dept_Mgr_Number)

VALUES (1022, 'Engineering CPU', 100341);

UPDATE Employee SET Dept_Number = 1022 WHERE Employee_Number = 100341;

To Insert

rows:

DELETE Employee WHERE Employee_Number= 100341; (error, referencing column)

UPDATE Department SET Dept_Mgr_Number = NULL WHERE Dept_Number = 1022 ;

DELETE Employee WHERE Employee_Number= 100341; (success)

To Delete

rows:

Note: FK1 and FK2 must allow NULLs for these operations to work.

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Referential Integrity Example

CREATE SET TABLE Employee

( employee_number INTEGER NOT NULL PRIMARY KEY,dept_number INTEGER

,emp_mgr_number INTEGER

,job_code INTEGER

,last_name CHAR(20)

,first_name VARCHAR(20)

,salary_amount DECIMAL(10,2) ) ;

CREATE SET TABLE Department

( dept_number INTEGER NOT NULL PRIMARY KEY

,dept_name CHAR(20) NOT NULL UNIQUE

,dept_mgr_number INTEGER

,budget_amount DECIMAL (10,2) ) ;

CREATE SET TABLE Job

( job_code INTEGER NOT NULL PRIMARY KEY,job_desc CHAR(20) NOT NULL UNIQUE ) ;

CREATE SET TABLE Emp_Phone

( employee_number INTEGER NOT NULL

,area_code SMALLINT NOT NULL

,phone_number INTEGER NOT NULL

,extension INTEGER

, PRIMARY KEY (employee_number, area_code, phone_number) )PRIMARY INDEX (employee_number);

Create the tablesspecifying the

Primary Keys.

Before creating the

References

constraints,

populate the tableswith user data.

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Referential Integrity Example (cont.)

ALTER TABLE EmployeeADD CONSTRAINT emp_dept_ref

FOREIGN KEY (dept_number) REFERENCES

Department (dept_number);

ALTER TABLE Employee

ADD CONSTRAINT emp_job_ref

FOREIGN KEY (job_code) REFERENCES

Job (job_code);

ALTER TABLE Employee

ADD CONSTRAINT emp_mgr_ref

FOREIGN KEY (emp_mgr_number) REFERENCES

Employee (employee_number);

ALTER TABLE DepartmentADD CONSTRAINT dept_mgr_ref

FOREIGN KEY (dept_mgr_number) REFERENCES


ALTER TABLE Emp_Phone

ADD CONSTRAINT phone_emp_ref

FOREIGN KEY (employee_number) REFERENCES


After populating the tableswith data, ALTER the tables

to create the References

constraints.

Notes:

The Employee table will have3 Reference Index subtables

created for it.

Error tables will be created

identifying rows where a FK

value does not exist in the

PK column(s).

Employee_0

Employee_4

Employee_8

Department_0

Emp_Phone_0

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Referential Integrity Example (cont.)

The tables (previous example) are shown below with the necessary indexesneeded to support this RI example.

EMPLOYEE

EMP

EMPLOYEE DEPT MGR JOB LAST

NUMBER NUMBER NUMBER CODE NAME

PK FK FK FKUPI

DEPARTMENT

DEPT

DEPT DEPT MGR BUDGETNUMBER NAME NUMBER AMOUNT

PK FK

UPI USI

JOB

JOB JOB

CODE DESC

PKUPI USI

EMP_PHONE

EMPLOYEE AREA PHONENUMBER CODE NUMBER EXTENSION

PK

FK

NUPI

USI

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Referential Integrity Views

View Description

DBC.All_RI_Children Information about all tables in child-parent order.

DBC.All_RI_Parents Information about all tables in parent-child order.

DBC.RI_Distinct_Children Reduces subset (eliminates duplicates) - information

about all tables in child-parent order.

DBC.RI_Distinct_Parents Reduces subset (eliminates duplicates) - information

about all tables in parent-child order.

DBC.RI_Child_Tables Provides internal table IDs of all tables in child-parentorder.

DBC.RI_Parent_Tables Provides internal table IDs of all tables in parent-child

order.

Examples are only provided of the first two views.

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DBC.All_RI_Children View

Provides information about all tables in child-parent order.

SELECT Indexid (FORMAT z9) AS ID

,IndexName

,ChildTable

,ChildKeyColumn

,ParentTable

,ParentKeyColumn

FROM DBC.ALL_RI_Children

WHERE ChildDB = USERORDER BY 3, 4 ;

Example Results:

Example:

List all of the referential

integrity constraints in

the child database.

DBC.All_RI_Children

IndexID IndexName ChildDB ChildTable

ChildKeyColumn ParentDB ParentTable ParentKeyColumn

InconsistencyFlag CreatorName CreateTimeStamp

ID IndexName ChildTable ChildKeyColumn ParentTable ParentKeyColumn

0 dept_mgr_ref Department dept_mgr_number Employee employee_number

0 emp_dept_ref Employee dept_number Department dept_number

8 emp_mgr_ref Employee emp_mgr_number Employee employee_number

4 emp_job_ref Employee job_code Job job_code0 phone_emp_ref Emp_Phone employee_number Employee employee_number

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DBC.All_RI_Parents View

Provides information about all tables in parent-child order.

SELECT Indexid (FORMAT 'z9') AS ID

,IndexName

,ParentTable

,ParentKeyColumn

,ChildTable

,ChildKeyColumn

FROM DBC.ALL_RI_Parents

WHERE ParentDB = USERORDER BY 3, 4 ;

Example Results:

Example:

List all of the referential

integrity constraints in

the parent database.

DBC.All_RI_Parents

IndexID IndexName ParentDB ParentTable

ParentKeyColumn ChildDB ChildTable ChildKeyColumn


ID IndexName ParentTable ParentKeyColumn ChildTable ChildKeyColumn

0 emp_dept_ref Department dept_number Employee dept_number

0 phone_emp_ref Employee employee_number Emp_Phone employee_number

0 dept_mgr_ref Employee employee_number Department dept_mgr_number

8 emp_mgr_ref Employee employee_number Employee emp_mgr_number4 emp_job_ref Job job_code Employee job_code

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Additional RI Views

These two additional views can be used to reduce duplicate rows for multi-column

foreign keys.

DBC.RI_DISTINCT_Children

IndexID IndexName ChildDB ChildTable ParentDB

ParentTable InconsistencyFlag CreatorName CreateTimeStamp

DBC.RI_DISTINCT_Parents

IndexID IndexName ParentDB ParentTable ChildDBChildTable InconsistencyFlag CreatorName CreateTimeStamp

These two additional views can be used if internal Table ID information is needed.

DBC.RI_Child_Tables

IndexID IndexName ChildDbID ChildTID ChildKeyFIDParentDbID ParentTID ParentKeyFID InconsistencyFlag CreatorName

CreateTimeStamp

DBC.RI_Parent_Tables

IndexID IndexName ParentDbID ParentTID ParentKeyFID

ChildDbID ChildTID ChildKeyFID InconsistencyFlag CreatorNameCreateTimeStamp

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Using the DBC.Tables View

SELECT TableName,TableKind

,ParentCount

,ChildCount

FROM DBC.Tables

WHERE DatabaseName = 'TFACT'

AND TableKind = 'T'ORDER BY 2, 1 ;

Example Results:

Example:List the tables objects

in the database TFACT

and identify parent

and child counts.

TableName TableKind ParentCount ChildCount

Department T 1 1

Employee T 3 3

Emp_Phone T 1 0

Job T 0 1Salary_Log T 0 0

The DBC.Tables view (shown previously) can be used to list parent and child

counts for tables. ParentCount how many foreign keys does a table have or how many parents does

the table reference?

ChildCount how many foreign keys reference this table or how many children does

the table have?

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Referential Integrity States

The status of a Referential integrity constraint is classified as follows:

Unresolved reference constraints-the FK exists, but the PK does not.

Creating a table with a Foreign Key before creating the table with Parent

Key (Primary Key).

Restoring a table with a Foreign Key and the Parent Key (Primary Key) table

does not exist or hasn't been restored.

Inconsistent reference constraint- both the FK and the PK exist, but the

constraint is marked as inconsistent.

When either the child or parent table is restored, the reference constraint

for the child table is marked as inconsistent. no inserts, updates, deletes or table changes allowed

Invalid Rows- both the FK and the PK exist and are considered

consistent, but specific foreign key values are identified as invalid.

Typically occurs when the reference constraints are created on already

populated tables or

Following a REVALIDATE REFERENCES command after a restore of eitherthe child or parent table.

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Unresolved Reference Constraints

The DBC.Databases2 view provides information about unresolved reference

constraints.

Unresolved reference constraints are caused by:

Creating a table with a Foreign Key before creating the table with Parent Key

(Primary Key).

Restoring a table with a Foreign Key and the Parent Key (Primary Key) table does not

exist or hasn't been restored.

DatabaseName DatabaseID UnresolvedRICountDBC.Databases2

Example: List all databases with

unresolved references.

DatabaseName DatabaseID UnresolvedRICount

PD 0000FE03 2

Results:

Restore the Parent Table to resolve the

references constraint, but the referencesconstraint is marked as inconsistent.

SELECT DatabaseName

,DatabaseId

,UnresolvedRICount

FROM DBC.Databases2

WHERE UnresolvedRICount > 0;

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Inconsistent Reference Constraints

When either the child or parent table is restored, the reference constraint is

marked as inconsistent.The DBC.All_RI_Children View can be used to identify tables with inconsistent

references following a restore operation.

IndexID IndexName ChildDB ChildTable

ChildKeyColumn ParentDB ParentTable ParentKeyColumn


ID IndexName ChildTable ChildKeyColumn ParentTable ParentKeyColumn ICF

0 dept_mgr_ref Department dept_mgr_number Employee employee_number Y

0 emp_dept_ref Employee dept_number Department dept_number Y

8 emp_mgr_ref Employee emp_mgr_number Employee employee_number Y

4 emp_job_ref Employee job_code Job job_code Y0 phone_emp_ref Emp_Phone employee_number Employee employee_number Y

DBC.All_RI_Children

Example: SELECT IndexID (FORMAT 'z9') AS ID,IndexName

,ChildTable ,ChildKeyColumn

,ParentTable ,ParentKeyColumn

,InconsistencyFlag AS ICF

FROM DBC.ALL_RI_ChildrenWHERE ChildDB = 'PD'

ORDER BY 3, 4 ;

Results:

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Handling Inconsistent References

When a table has an inconsistent reference, changes are not allowed to the

child key table (no inserts, updates, or deletes).

Options to handle inconsistent references.

DROP INCONSISTENT REFERENCES. The FK Constraints are now removed

from the table. Use the ALTER TABLE command to create new References

constraint(s).

Use the REVALIDATEREFERENCES command (ARC facility).

If a references constraint is created or revalidated, the foreign key values are

validated against PK values. FK values (missing from the PK) are marked as

invalid in the RI subtable and an error table is created (e.g., EMPLOYEE_0).

Warning: Proceed with caution!

ALTER TABLE child_table DROP INCONSISTENT REFERENCES;

FK Constraints are now removed from the table and the table may be updated withinconsistent foreign key values before the References constraint is created.

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What is a Trigger?

A Trigger may be defined as:

One or more stored SQL statementsassociated with a table

An event driven procedure attached

to a table

An object in a database, like tables,

views and macros

CREATE

DROP

SHOW

ALTER

RENAME

REPLACE

HELP

TRIGGERS

Triggers may not be used in conjunction

with:

The FastLoad utility

The MultiLoad utility

Updateable Cursors

DELETE DATABASE or DELETE USER cause all triggers to be dropped.

Privileges are required to create and drop triggers.

Any of the following SQL statements may be applied to triggers:

GRANT

REVOKE

CREATE

DROP TRIGGER

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Access Rights and Triggers

Example: CREATE TRIGGER trigger1

AFTER UPDATE OF (col1) ON table1 FOR EACH ROWWHEN NEW col1 > 100

INSERT INTO log_table VALUES .

Access Rights to Create Triggers

CREATE TRIGGER privilege on the subject table or the database.

SELECT privilege on any column referenced in a WHEN clause or a triggered SQL

statement subquery.

INSERT, UPDATE, or DELETE privileges on the triggered SQL statement target table,

depending on the triggered SQL statement.

Access Rights to Replace Triggers DROP TRIGGER privilege on the subject table or the database. The exception is

when you use the REPLACE TRIGGER statement when no target trigger exists and

you instead create a new trigger.

SELECT privilege on any column referenced in a WHEN clause or a triggered SQL

statement subquery.

INSERT, UPDATE, or DELETE privileges on the triggered SQL statement target table,depending on the triggered SQL statement.

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Trigger Example

CREATE SET TABLE Employee

(Name CHAR(15),Deptid INTEGER,

Salary DECIMAL(10,2),

Job_Title CHAR(15))

PRIMARY INDEX (Name);

CREATE SET TABLE Salarylog

(UserName CHAR(30),EmpName CHAR(30),

OldSalary DECIMAL(10,2),

NewSalary DECIMAL(10,2))

PRIMARY INDEX (UserName);

Create a trigger that places a new row into the Salarylog table whenever there is a salary

increase greater than 10%.

CREATE TRIGGER RaiseTrig

AFTER UPDATE OF (Salary) ON Employee

REFERENCING OLD AS OldRow NEW AS NewRow

FOR EACH ROW

WHEN ((NewRow.Salary - OldRow.Salary)/OldRow.Salary > 0.10)

( INSERT INTO SalaryLogVALUES (USER, NewRow.Name, OldRow.Salary, NewRow.Salary); );

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Trigger Example (cont.)

SELECT * FROM Employee; SELECT * FROM Salarylog;

Name Deptid Salary Job_Title *** Query completed. 0 row(s) found. 4

========= ====== ======= ========= field(s) returned.carol 3333 32000.00 directordebbie 4444 40000.00 presidentlarry 2222 22000.00 instructor

joe 2222 30000.00 instructorallan 1111 20000.00 consultant

UPDATE Employee SET salary = salary * 1.25 WHERE name = 'allan';UPDATE Employee SET salary = salary * 1.05 WHERE name = 'debbie';

UPDATE Employee SET salary = 50000 WHERE name = 'carol';

SELECT * FROM Employee;

Name Deptid Salary Job_Title

========= ====== ======= =========carol 3333 50000.00 director

debbie 4444 42000.00 presidentlarry 2222 22000.00 instructor

joe 2222 30000.00 instructorallan 1111 25000.00 consultant

SELECT * FROM Salarylog;

UserName EmpName OldSalary NewSalary

========= =========== ======== =========

PAYADMIN allan 20000.00 25000.00PAYADMIN carol 32000.00 50000.00

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Referential Integrity and Triggers Summary

Referential integrity is a concept of relationships between tables based on

the definition of a primary key and a foreign key in the tables.

Referential integrity prevents database corruption when application users

execute INSERT, UPDATE and DELETE statements.

When referential integrity is applied, columns within a referencing tableare foreign keys for columns in another referenced table. You must define

referenced columns as either:

Primary key columns, or UNIQUE columns

NOT NULL

To create or replace triggers, you need specific privileges.

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Review Questions

1. Number the following steps 1 to 3 based on the recommendations of this module.

___ Create references___ Create data tables

___ Populate the tables

2. Answer the following statements about Primary and Foreign Keys as true or false.

___ A PK value can be set to NULL as long as there are no FK values referencing

that PK value.

___ A PK value can be set to a different value as long as there are no FK values

referencing that PK value.

___ A FK value can be set to NULL.

___ A PK can be implemented as a NOT NULL NUPI.

___ A FK can only be implemented on indexed columns.

___ A PK is always implemented as a UNIQUE INDEX.

3. A trigger executes (fires) when either an ______, ______, or _______ statement modifies

a specified column or columns in a table.

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Lab Exercises

Lab Exercise 9-1

Purpose

In this lab, you will use BTEQ or (Teradata SQL Assistant) to establish References constraints between

4 populated tables and view the associated data dictionary entries.

What you need

Populated PD tables and empty tables in your database

Tasks1. Use INSERT/SELECT to place all rows from the populated PD tables into your empty tables. Verify the

number of rows in your tables.

PD.Employee to populate Employee Count = _______

PD.Department to populate Department Count = _______

PD.Job to populate Job Count = _______

PD.Emp_Phone to populate Emp_Phone Count = _______

2. Use the GRANT statement to GRANT yourself the REFERENCES access rights on the tables.

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Lab Exercises

Lab Exercise 9-1 (cont.)

Tasks3. Create a References constraint between the Employee.Dept_Number column and the

Department.Dept_Number column.

What is the name of the Employee RI error table? _______________

How many rows are in this table? ______

Which department is not represented in the department table? _______

4. Use the DBC.All_RI_Children view (qualify the ChildDB to your database) and verify this References

constraint.

What is the IndexID of this constraint? _______

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Lab Exercises


Tasks5. Create the References constraint between the Employee.Job_code column and the Job.Job_Code

column.



Which job code is not represented in the job table? _______


constraint.

What is the IndexID of this constraint? ________

7. Create the References constraint between the Employee.Emp_Mgr_Number column and the

Employee.Employee_Number column.



Which employee does not have a manager (Emp_Mgr_Number is 0 or NULL)? _______


constraint.


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Lab Exercises


Tasks9. Create a References constraint between the Department.Dept_Mgr_Number column and the


What is the name of the Department RI error table? _______________


10. Use the DBC.All_RI_Children view (qualify the ChildDB to your database) and verify this Referencesconstraint.


11. Create a References constraint between the Emp_Phone.Employee_Number column and the


What is the name of the Emp_Phone RI error table? _______________How many rows are in this table? ______


constraint.


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Lab Solutions for Lab 9-1

Lab Exercise 9-1

1. Use INSERT/SELECT to place all rows from the populated PD tables into your empty tables. Verify the number ofrows in your tables.

INSERT INTO Employee SELECT * FROM PD.Employee;

SELECT COUNT(*) FROM Employee; Count = 1000

INSERT INTO Department SELECT * FROM PD.Department;

SELECT COUNT(*) FROM Department; Count = 60

INSERT INTO Job SELECT * FROM PD.Job;

SELECT COUNT(*) FROM Job; Count = 66

INSERT INTO Emp_Phone SELECT * FROM PD.Emp_Phone

SELECT COUNT(*) FROM Emp_Phone; Count = 2000

2. Use the GRANT statement to GRANT yourself the REFERENCES access rights on the tables.

GRANT REFERENCES ON Employee TO tljc20;

GRANT REFERENCES ON Department TO tljc20;

GRANT REFERENCES ON Job TO tljc20;

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3. Create a References constraint between the Employee.Dept_Number column and the Department.Dept_Numbercolumn.

ALTER TABLE Employee ADD CONSTRAINT emp_dept_ref

FOREIGN KEY (dept_number) REFERENCES

Department (dept_number) ;

What is the name of the Employee RI error table? EMPLOYEE_0

How many rows are in this table? 1Which department is not represented in the department table? 1000

4. Use the DBC.All_RI_Children view (qualify the ChildDB to your database) and verify this References constraint.

What is the IndexID of this constraint? 0

SELECT Indexid (FORMAT 'z9') AS ID,IndexName

,ChildTable,ChildKeyColumn,ParentTable,ParentKeyColumn

FROM DBC.ALL_RI_ChildrenWHERE ChildDB = USERORDER BY 3, 4 ;

ID IndexName ChildTable ChildKeyColumn ParentTable ParentKeyColumn0 emp_dept_ref Employee dept_number Department dept_number

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5. Create a References constraint between the Employee.Job_code column and the Job.Job_Code column.

ALTER TABLE Employee ADD CONSTRAINT emp_job_ref

FOREIGN KEY (job_code) REFERENCES Job (job_code);


How many rows are in this table? 1

Which job code is not represented in the job table? 3000



SELECT Indexid (FORMAT 'z9') AS ID,IndexName,ChildTable

,ChildKeyColumn,ParentTable,ParentKeyColumn

FROM DBC.ALL_RI_ChildrenWHERE ChildDB = USERORDER BY 3, 4 ;



4 emp_job_ref Employee job_code Job job_code

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7. Create a References constraint between the Employee.Emp_Mgr_Number column and theEmployee.Employee_Number column.

ALTER TABLE Employee ADD CONSTRAINT emp_mgr_ref

FOREIGN KEY (emp_mgr_number) REFERENCES Employee (employee_number);



Which employee does not have a manager (Emp_Mgr_Number is 0 or NULL)? 100001

SELECT * FROM Employee WHERE emp_mgr_number = 0:



SELECT Indexid (FORMAT 'z9') AS ID ,IndexName

,ChildTable ,ChildKeyColumn,ParentTable ,ParentKeyColumn


WHERE ChildDB = USER

ORDER BY 3, 4 ;



8 emp_mgr_ref Employee emp_mgr_number Employee employee_number4 emp_job_ref Employee job_code Job job_code

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9. Create a References constraint between the Department.Dept_Mgr_Number column and theEmployee.Employee_Number column.

ALTER TABLE Department ADD CONSTRAINT dept_mgr_ref

FOREIGN KEY (dept_mgr_number) REFERENCES Employee (employee_number);

What is the name of the Department RI error table? DEPARTMENT_0








WHERE ChildDB = USERORDER BY 3, 4 ;




8 emp_mgr_ref Employee emp_mgr_number Employee employee_number4 emp_job_ref Employee job_code Job job_code

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11. Create a References constraint between the Emp_Phone.Employee_Number column and theEmployee.Employee_Number column.

ALTER TABLE Emp_Phone ADD CONSTRAINT phone_emp_ref

FOREIGN KEY (employee_number) REFERENCES Employee (employee_number);

What is the name of the Emp_Phone RI error table? EMP_PHONE_0







FROM DBC.ALL_RI_ChildrenWHERE ChildDB = USER

ORDER BY 3, 4 ;




8 emp_mgr_ref Employee emp_mgr_number Employee employee_number

4 emp job ref Employee job code Job job code


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