Download Introduction to DB2

Introduction to DB2
Course Objective
•
To illustrate DB2 Architecture
•
To explain DB2 Objects
– Database, Table space, Table, Index
•
Datatypes DB2 support
•
Integrity
– Foreign keys
•
Security
– Views
– Grant and Revoke
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Course Objective
•
Embedded SQL
•
Program Preparation
– Precompile, Bind
– DBRM's, Plans, and Packages
– Compile a Cobol-DB2 Program
•
Concurrency and utilities
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Course Plan
•
Day 1: Overview of DB2
•
Day 2: SPUFI, DCLGEN & Embedded SQL
•
Day 3: Program Preparation and Execution
•
Day 4: OLTP Issues
•
Day 5: Project Evaluation and Final Test
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Prerequisites
•
MVS and TSO
•
Programming in COBOL
•
RDBMS Concepts
•
Working knowledge of SQL
•
OLTP Concepts
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Session Plan
•
To illustrate DB2 Architecture
•
To explain DB2 Objects
– Database, Tablespace, Table, Index
•
Datatypes DB2 support
•
Integrity
– Foreign keys
•
Security
– Views
– Grant and Revoke
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RDBMS Review
•
Database
•
Database Management System
•
Database Models
•
Relational Database Management System
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Introduction to DB2
•
What is DB2?
– A subsystem of the MVS operating system
– An abbreviation for ‘IBM Database 2’
– Was announced in June 1983
– Supports SQL (Structured Query Language)
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System Architecture
•
Major Components of DB2
– SSAS (System Services Address Space)
• Thread creation, Program tracing, Logging
– DBAS (Database Services Address Space)
• Execution of SQLs, Database objects management, buffer
management, Data read/write, etc.
– IRLM (IMS Resource Lock Manager)
• Locking
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System Architecture
Major Components of DB2
– DDF (Distributed data facility component ) is optional
• Distributed Database functionality
– SPAS (Stored Procedure Address Space)
• For the execution of the stored procedures
•
Each of these components runs in a separate address space
and is made up of numerous sub-components.
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DB 2 System Architecture
DSNMSTR
DSNDBM1
IRLMPROC
DSNDDF
SSAS
DBAS
IRLM
DDF (Optional)
Database functions
Locking
Distributed
Requests
Logging
Attachment
co-ordination
Buffering
Free Space
Free Space
MVS Common Area
MVS Common Area
Free Space
MVS Common Area
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Free Space
MVS Common Area
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System services component- (Contd..)
•
Handles DB2 startup and shutdown.
•
Control and co-ordinate connections to other MVS subsystems such as
CICS, IMS and TSO.
•
Manages the System log. The system log is a set of datasets that
used to record information about every transaction.
•
Is responsible for establishing and maintaining all the threads for DB 2.
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System services component - (Contd..)
•
Has a sub-component called Instrumentation facility.
•
The instrumentation facility gathers statistical information about the work
done by DB 2 at user specified intervals of time.
•
This information is either
–
Written to a System Management facility (SMF) or Generalized Trace
Facility (GTF) dataset or
–
Passed to a performance monitor program provided some third party
vendor.
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Database services component
•
Is responsible for execution of SQL statements and management of Buffer
pools.
•
Comprises of 3 major sub-components Viz.
1.Relational Data System (RDS)
2.Data Manager (DM) and
3.Buffer Manager (BM)
•
The RDS manages Stage 2 predicates , does Auth check , SQL statement
checking , Sorting and Optimizer
•
The DM is responsible for managing the data at the physical level. Does Stage
1 predicates , Indexable predicates and DML
•
The DM invokes other system components for performing functions such as
locking, logging, etc.,
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Database services component - (Contd..)
•
The BM manages all the Buffer pools required by DB 2 for database
operations. It keeps the frequently used pages in the buffer.
•
The BM is responsible for opening and closing all the datasets used by
application data and work areas.
•
The BM instructs the Data Facility Product (DFP) to do a physical I/O as and
when required.
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STAGE 1 PREDICATES
COLUMN_NAME operator VALUE
COLUMN_NAME IS NULL
COLUMN_NAME BETWEEN val1 AND val2
COLUMN_NAME IN List
COLUMN_NAME LIKE pattern
COLUMN_NAME LIKE :Host-variable
A.COLUMN_NAME1 operator B.COLUMN_NAME2
COLUMN_NAME Operator (non correlated sub query)
COLUMN_NAME Operator (non column expression)
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STAGE 1 / 2 PREDICATES
CORRELATED
SELECT EMP,LASTNAME
FROM EMP A
WHERE EXISTS
(SELECT 1 FROM DEPT B
WHERE A.DEPTNO=B.DEPTNO
AND DEPTDESC=‘EDUCATION’)
NON CORRELATED
SELECT EMP,LASTNAME
FROM EMP A
WHERE DEPTNO IN
(SELECT DEPTNO FROM DEPT
WHERE DEPTDESC=‘EDUCATION’)
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FROM RDS to DM to BM and back
-- > SQL
Results
Relational
Data
System
Optimized
SQL
Read Buffer
Or Request
Data
Data
Manager
Apply Stage 2
Predicates & Sort
Data
Apply Stage 1
Predicates
Buffer
Manager
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VSAM Media
Manager
DATA
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Locking Services Component
•
The locking services are provided by a component called Integrated
Resource Lock Manager (IRLM).
•
The IRLM takes care of all the concurrency control issues.
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Distributed Data Facility Component
•
Provides distributed database functionality.
•
Is an optional component.
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Threads
•
Are memory structures used by DB 2 to communicate with an application
program.
•
Serves as links between DB 2 and application programs.
•
Application programs send all requests to DB 2 through threads.
•
DB 2 communicates the status of each SQL statement to the application
using threads through SQLCA.
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Threads
CICS
PGM
Call
Attach
pgm
IMS/DC
PGM
TSO
O/L
PGM
DB2
Utility
TSO
Batch
pgm
DB2
QMF
Or
DB2I
IMS
Batch
pgm
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DB2 Objects
DATABASE
TABLESPACE
TABLE
INDEX
SYNONYM
VIEW
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DB 2 Objects Hierarchy
STOGROUP
DATABASE
TABLESPACE
VIEW
ALIAS
SYNONYM
TABLE
INDEX
COLUMN
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Storage Groups
•
Are a collection of one or more (maximum of 133) DASD volumes of the
same type.
•
Provides space for storing all the datasets that DB 2 uses.
•
Are created by System administrator as shown below.
CREATE STOGROUP STOUDB6
VOLUMES (DAVP7C, DAVP8C, DAVP9E)
PASSWORD infosys;
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Storage Groups - (Contd..)
•
The number volumes in a storage group can be changed dynamically as
shown below.
ALTER STOGROUP STOUDB6
ADD VOLUMES (DAVP9F, DAVP8C, DAVP9E)
REMOVE VOLUMES (DAVP7C, DAVP8C)
PASSWORD infosys;
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Database
•
Is a collection of one or more Tablespaces and Index spaces.
•
Generally every application will have a unique database. This simplifies
administrative tasks and also improves application performance.
•
One DB 2 system can manage up to 65,279 databases.
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Creating a Database
•
To create a database use
CREATE DATABASE EMPDB;
Maximum 8 characters name
CREATE DATABASE DBENR
STOGROUP STOUDB6
BUFFERPOOL (BP0, BP32);
•
To remove a database use
DROP DATABASE DBENR;
•
To change the definition use
ALTER DATABASE EMPDB
ALTER DATABASE DBENR
ROSHARE {OWNER, NONE}
STOGROUP STOUDB6;
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Database Descriptor (DBD)
•
Is a DB 2 component that is created whenever a database is created.
•
Stores control and descriptive information about every object in the
corresponding database.
•
Whenever a database is in use, the associated DBD is buffered.
•
To maintain database integrity the DBD is locked whenever an object is being
created, updated or deleted in the corresponding database.
•
Instead of accessing DB2 catalog for object information , DBD which is housed
in DB2 directory is accessed which is more efficient.
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Tablespace
•
A Tablespace is one or more VSAM datasets
•
Three types
– Segmented TS (default)
– Simple TS
– Partitioned TS (for large databases)
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Creating a TS
•
Created under an existing DB using
CREATE TABLESPACE EMPTS
IN EMPDB
PRIQTY 10000
SECQTY 1000
PCTFREE 10
FREEPAGE 63
LOCKSIZE ANY
BUFFERPOOL BP0
SEGSIZE 64
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More on TS
•
To remove a tablespace use
DROP TABLESPACE EMPTS
•
To change the definition use
ALTER TABLESPACE EMPTS
ALTER TABLESPACE DBENR.ENR
PRIQTY
200
SECQTY
200
ERASE
YES
LOCKSIZE
ANY
BUFFERPOOL BP1;
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Simple TS
•
Can house one or more tables
•
There is no limit for number of tables
•
Rows from multiple tables can be interleaved on a page
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Segmented TS
•
Can house one or more tables
•
TS is divided into segments of 4 to 64 pages in increments of 4
•
One segment contains data from exactly one table
•
One table can occupy many segments
•
Good for performance and this is DB2 default
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Partitioned tablespace
•
allows a table to be divided by rows into partitions
•
Each partition can be placed on different storage devices
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Table
•
A tablespace within a database can have any number of tables
•
Create table using
CREATE TABLE EMPLOYEE
(EMP_NO
EMP_NAME
SMALLINT
NOT NULL,
CHAR(15),
EMP_ADDRESS VARCHAR(25) NOT NULL
WITH DEFAULT,
PRIMARY KEY (EMP_NO));
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More on Table
•
To remove a table
DROP TABLE EMPLOYEE
•
To change the definition use
ALTER TABLE EMPLOYEE
For example, to add a new field
ALTER TABLE EMPLOYEE
ADD EMP_SALARY INTEGER
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Data types
Data Type
String
Character
Datetime
Graphic
Date
Timestamp
Numeric
Time
Integer
Fixed
Length
Decimal
Floating
Point
Variable
Length
Small
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Double
Data types- (Contd..)
•
Integer
– 4 bytes (5 if nullable)
– PIC S9(9) COMP
•
Smallint
– 2 bytes (3 if nullable)
– PIC S9(4) COMP
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Data types- (Contd..)
•
Char(n)
– max. 254 bytes
– PIC X(n)
•
Varchar(n)
– max. 4046 bytes
– A structure containing
PIC S9(4) COMP for length and
PIC X(n) for the data
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Data types- (Contd..)
•
Time
– 3 bytes (4 if nullable)
– PIC X(8)
•
Date
– 4 bytes (5 if nullable)
– PIC X(10)
•
Timestamp
– 10 bytes (11 if nullable)
– PIC X(26)
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Nulls
•
DB2 adds an extra byte to all nullable columns
•
This extra byte has the information whether the field contains NULL or not
•
The NULL values do not participate while taking AVERAGE, SUM, etc.
•
Need to have special care while inserting, updating, or retrieving nullable
fields in the host language program
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WITH DEFAULT
•
DB2 puts the default value of the data type in that field while inserting a record
•
For character fields, spaces,
for numeric fields, zeros,
for date fields, current date
for time fields, current time
... and so on
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Index
•
Is a structure used for faster retrieval of data.
•
Can be unique or non-unique.
•
In DB 2, we need to explicitly create a unique index for the primary key.
•
Is stored in B - Tree format.
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Root Page
Level 0
Non-Leaf Page1
Level 1
100
200
300
400
L1
L2
L3
L4
1000
2000
3000
4000
Index
Leaf Page 1
Level 2
Leaf Page 2
Level 2
10
20
30
40
101 DP10.1
102 DP10.2
...........
151 DP20.1
DP1
DP2
DP3
DP4
Data Page 10
101 Roopa
19
102 Deeptha
20
..................
NL1
NL2
NL3
NL4
Infosys Technologies Ltd
1100
1200
1300
1400
L11
L12
L13
L14
Leaf Page 12
Level 2
1101 DP50.1
1102 DP50.2
............
............
Data Page 50
Data Page 20
151 Bhavana
20
. . . . .Copyright
. . . . . .©.2005,
......
Non-Leaf Page2
Level 1
45
1101 Vijay
22
1102 Harish
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. . . . No:2.0b
............
Index – (Contd…)
•
Root Page
Only one root page is available per Index.It should exist at the highest
level of the hierarchy.It can be structured as Leaf pages or Non leaf
pages.
•
Non Leaf pages
Non Leaf pages are intermediate-level Index pages in the b-tree
hierarchy. It need not exist.If they exist they contain the pointers to the
Leaf pages.
•
Leaf Pages
Leaf pages contain pointers to the data rows of a table.Leaf page must
always exist. In a single page Index, the root page is a Leaf page
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Index – (Contd…)
•
Columns that are good for indexing
1.
Primary key and Foreign key columns,
2.
Column having unique values,
3.
Columns that are frequently used in the WHERE clause and
4.
Columns that frequently used in an ORDER BY, GROUP BY and
DISTINCT clauses.
•
Columns that are not good for indexing
1.
Frequently updated,
2.
Longer than 30 characters and
3.
Containing redundant values.
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Creating Index 1 of 2
•
DB2 creates Index spaces for every index (one index space for one
index)
•
Is a page set used to store information about one index.
•
Only one index per index space.
•
Index space pages are 4k pages.
•
Contains value from indexed columns and an RID to the corresponding
row.
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Creating Index 2 of 2
•
An index and its associated table must be in the same database
•
Index pages can be locked by sub page increments (1/2, 1/4, 1/8 and
1/16). The default is 1/4.
•
Often the response time will be slow due to Indexspace lock contention
rather than Tablespace lock contention. In such cases the response time
can be improved by increasing the value of the SUBPAGE parameter.
•
Indexes are created using
CREATE [UNIQUE] INDEX EMPNOINDX
ON EMPLOYEE(EMP_NO ASC)
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More on Index
•
To remove an index
DROP INDEX EMPNOINDX
•
To change the definition use
ALTER INDEX EMPNOINDX
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Clustered index (1 of 2)
•
Data is physically ordered in the sequence of the index.
•
Only one clustering index per table.
•
Good for columns
–
used in BETWEEN , >, <, LIKE
–
used in GROUP BY, ORDER BY, DISTINCT
–
for PRIMARY and FOREIGN KEYS
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Clustered index – (Contd…)
CREATE INDEX CLUSTER_EMP_INX ON ENR.EMP
(EMPNO ASC)
PRIQTY 36
CLUSTER
(PART 1 VALUES('H99'),
PART 2 VALUES('P99'),
PART 3 VALUES('Z99'),
PART 4 VALUES('999'))
BUFFERPOOL BP1;
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Catalog Tables
•
When tables and other objects are created, DB2 records all these information
into a set of system tables called “catalog tables”
•
SYSDATABASE, SYSTABLESPACE, SYSTABLES, SYSCOLUMNS,
SYSINDEXES, SYSVIEWS, etc. are examples
•
If you have authority, you can query on these tables as any other table
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Synonyms and Aliases
•
Are used for creating alternate names for existing tables.
•
Synonyms can refer only to local tables.
•
Aliases can refer to both local as well as remote tables. In fact aliases were
designed for distributed environment to avoid references to the location
qualifier.
•
When a table is dropped all the synonyms get dropped automatically where as
aliases on that table remains.
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Synonyms and Aliases
• CREATE SYNONYM EMP FOR EMPDB.EMPLOYEE
• CREATE ALIAS EMP FOR BANGALORE.EMPDB.EMPLOYEE
•
Use DROP to drop these objects
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Integrity
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Referential Integrity
•
Suppose you want to make sure that all the employee numbers in
PROJ_ALLOCATION(PROJ_ID,EMP_NO) are valid employees and
valid projects (i.e., they belong to EMPLOYEE(EMP_NO,EMP_NAME)
and PROJECT(PROJ_ID,PROJ_NAME) master tables
•
You use referential integrity support DB2 provides to enforce this
(through definition of foreign keys)
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Referential Integrity - Keys
•
Unique Key

A unique key is defined as a column (or set of columns) where no two values
same.

The columns of a unique key cannot contain null values.

A table can have multiple unique keys.

Unique keys are optional and can be defined in CREATE TABLE or ALTER
TABLE statements.
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Referential Integrity - Keys
•
Primary Key

A primary key is a unique key that is a part of the definition of the table.

A table cannot have more than one primary key, and the columns of a primary
key cannot contain null values.

Primary keys are optional and can be defined in CREATE TABLE or ALTER
TABLE statements.
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Referential Integrity - Keys
•
Foreign Key
A foreign key is a column (or set of columns) which is a primary key in another
table.
•
Unique Constraint


A unique constraint ensures that values of a key are unique within a table.
Unique constraints are optional, and can be defined CREATE TABLE or ALTER
TABLE statements by specifying the PRIMARY KEY or UNIQUE clause.
For example, Unique constraint can be defined on the employee number
column of a table to ensure that every employee has a unique number.

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Creating a Foreign key
• CREATE TABLE
PROJ_ALLOCATION
(PROJ_ID
EMP_NO
CHAR(8) NOT NULL,
SMALLINT NOT NULL,
PRIMARY KEY(PROJ_ID,EMP_NO),
FOREIGN KEY PROJ_FK(PROJ_ID) REFERENCES PROJECT(PROJ_ID),
FOREIGN KEY EMP_FK(EMP_NO)
REFERENCES
EMPLOYEE(EMP_NO)
)
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Delete Rules
•
What happens if one employee is deleted from employee master table?
•
DB2 supports 3 delete rules
– DELETE RESTRICT
– DELETE CASCADE
– DELETE SET NULL
•
When defining foreign keys give these rules
FOREIGN KEY PROJ_FK(PROJ_ID) REFERENCES PROJECT(PROJ_ID)
DELETE CASCADE
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Referential Integrity
Employee Table
Dept No
1000
1001
1002
EmpName
Hari
Girish
Sunitha
Invalid Record
1005
Usha
Foreign key
Primary key
Dept No
1000
1001
1002
1004
Dept Name
Sales
Marketing
Training
Finance
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Department Table
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Foreign Key Rules – Delete on Cascade
Department Table
Dept No
Dept name
1000
2000
Training
Sales
When dept No : 1000 is deleted then..
Employee Table
Empname Dept No
Tim
1000
Jim
1000
Tom
2000
Mary
1000
The child records are also deleted automatically
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Foreign Key Rules – Delete on Restrict
Department Table
Dept No
Dept name
1000
2000
Training
Sales
When dept No : 1000 is deleted then..
It gives an error and cannot delete as there are
child records for the parent record.
Employee Table
Empname Dept No
Tim
1000
Jim
1000
Tom
2000
Mary
1000
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Foreign Key Rules – Delete on SET NULL
Department Table
Dept No
Dept name
1000
2000
Training
Sales
When dept No : 1000 is deleted then..
Employee Table
Empname Dept No
Tim
Jim
Tom
2000
Mary
The child records foreign key values are set to
Null
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Self Referencing Tables
•
Consider this table
EMPLOYEE(EMP_NO, PL_EMP_NO)
• PL_EMP_NO is a foreign key referencing to the EMP_NO field of the same table
•
DB2 does not allow creation of these foreign keys while creating tables
•
We need to use ALTER TABLE to add the foreign key constraint later
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Security
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Security
•
Security means the protection of the data in the data base against
unauthorized disclosure, alteration or destruction.
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Views
•
Unlike actual tables, views defined on a table are just definitions
•
DB2 keeps all view definitions in SYSVIEWS catalog table
•
All the views depend on one or more tables or views
•
We can have views created using other views
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Creating a View
CREATE VIEW RICH_EMP AS
SELECT EMP_NO, EMP_NAME
•
FROM
EMPLOYEE
WHERE
SALARY > 25000
Now we can use
SELECT EMP_NO, EMP_NAME
FROM RICH_EMP
in our program
•
Views provide
– security, independence from the base tables
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Updating using a View
•
DB2 allows updation of only “simple” views
•
You can issue update statement as if you are updating an actual table
•
DB2 does not allow you to update
– views using joins
– views using DISTINCT and aggregates
– views using GROUP BY
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More on View
•
Like any other object, use
DROP VIEW RICH_EMP to delete a view
•
When a table or a view is dropped all dependent views are automatically
dropped
•
DB2 does not allow you to create views with ORDER BY, FOR UPDATE OF, or
UNION
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GRANT
•
Use GRANT keyword to grant permissions on database objects
GRANT SELECT
ON EMPLOYEE TO PUBLIC;
GRANT UPDATE (EMP_ADDRESS)
ON EMPLOYEE TO SMITH;
GRANT INSERT, DELETE
ON EMPLOYEE TO TRAINEES;
•
A table creator has implicit authority to
– alter, drop, create a view/index, select/insert/update/delete
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REVOKE
•
Use REVOKE keyword to take away permissions on database objects
REVOKE SELECT
ON EMPLOYEE FROM PUBLIC;
REVOKE UPDATE (EMP_ADDRESS)
ON EMPLOYEE FROM SMITH;
REVOKE INSERT, DELETE
ON EMPLOYEE FROM TRAINEES;
REVOKE ALL
ON EMPLOYEE FROM PUBLIC;
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More on Permissions
•
You can GRANT a privilege to someone with GRANT option
GRANT ALL ON EMPLOYEE TO PUBLIC
WITH GRANT OPTION;
•
Suppose Jones grants select permission on view RICH_EMP to Smith with
grant option; Smith in turn grants select permission to Adams on the same
view; What happens if Jones revokes permission from Smith?
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BUNDLED PRIVILEGES
•
SYSDM
•
SYSCTRL
•
DBADM
•
DBCTRL
•
DBMAINT
•
SYSOPR
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Summary
•
DB2 Architecture
•
DB2 Objects
– Database, Tablespace, Table, Index
•
Datatypes DB2 support
•
Integrity
– Foreign keys
•
Security
– Views
– Grant and Revoke
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Thank You!
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