db2 working with databases and database objects

8/6/2019 DB2 Working With Databases and Database Objects

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IBM DB2 9

2008 IBM Corporation

Section -3) Working withWorking withDatabases and Database ObjectsDatabases and Database Objects

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Section 3Section 3 -- Working with Databases andWorking with Databases and

Database Objects (17%)Database Objects (17%)

Ability to identify and connect to DB2 serversAbility to identify and connect to DB2 servers

and databasesand databases

Ability to identify DB2 objectsAbility to identify DB2 objects

Knowledge of basic characteristics andKnowledge of basic characteristics and

properties of DB2 objectsproperties of DB2 objects

Given a DDL SQL statement, ability to identifyGiven a DDL SQL statement, ability to identify

results (ability to create DB2 objects)results (ability to create DB2 objects)

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Servers, Instances, and Databases

During the installation process, program files for a background

process known as the DB2 Database Manager are physically

copied to a specific location on the server.

A DB2 instance is a logical database server environment.

There can be multiple DB2 instances on a server. Multiple

Databases can be created within a DB2 instance.

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More on instances

The default instance for a particular system is defined by the

DB2INSTANCE environment variable. Initially for Windows

default is DB2 and for Linux/Unix it is db2inst1.

DB2 9 Instance Management Commands:

Command Purpose

db2icrt [InstanceName] Creates a new instance

db2idrop [InstanceName] Deletes (drops) an existing instance

db2ilist Lists all instances that have been defined

db2start Starts the DB2 Database Manager background

processes for the current instance

db2stop Stops the DB2 Database Manager background

processes for the current instance


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DB2 Storage Model

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DB2 Storage Model

A database is created within an instance.- There may be multiple databases managed by a DB2

instance

Logical storage model:- Tables are made up of columns and rows

- Tables are placed into table spaces

- Table spaces can contain more than one table

Physical storage model:- Containeris a physical storage device

- Can be a directory, a device, or a file

- Container is assigned to a table space

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Tablespaces

A tablespace is a logical layer between data and storagedevices.

- Consists of one or more containers.

- Tables, regular data, indexes, and long data reside in

tablespacesSQL: CREATE / DROP / ALTER TABLESPACE

To display Table space info:

- LIST TABLESPACES [SHOW DETAIL]

Details about containers can be obtained with followingcommand.

- LIST TABLESPACE CONTAINERS FOR tablespace_id[SHOW DETAIL]

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Types of Tablespaces

System-Managed Space (SMS):

- OSs file system manager allocates and manages the space.

Database-Managed Space (DMS):

- Here, the database manager controls the storage space.

Automatic Storage With DMS:- Databases that are enabled for automatic storage have a set

of one or more storage paths associated with them.

- A table space can be defined as "managed by automaticstorage" and its containers assigned and allocated by DB2based on those storage paths.

- You cannot enable/disable automatic storage once it isdefined for database.

- Default type in DB2 9.


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Database

The database contains following objects:-Tables, views, indexes, schemas, Locks, triggers, stored

procedures, packages, Buffer pools, log files, table spaces

Tools, which can help you create DB2 9 database are FirstSteps, Control Center [ Using GUI Wizard ] and CommandLine Processor (CLP).

Some database commands -

CREATE DATABASE

To create a database. (Database name

can not begin with "SYS", "DBM", or "IBM)

CONNECT TO To connect to a database

CONNECT RESET To terminate connection

DROP DATABASE To drop database

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With database, DB2 automatically creates

Three table spaces are created.

- SYSCATSPACE - This is where the DB2 system

catalog is kept that tracks all of the metadata

associated with DB2 objects.

- TEMPSPACE1 A temporary work area where

DB2 can place intermediate results.

- USERSPACE1 A place where all user objects

(tables, indexes) reside by default.

Configuration information (DB CFG)

Log files, History files etc.

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Cataloging

DB2 automatically catalogs databases when they arecreated. It catalogs an entry for the DB in the local databasedirectory and another entry in the system database directory.

Without catalog information, an application cannot connect to a

DB. DB2 has multiple directories that are used to access DBs.- The database directory contains a list and pointer to where

all the known databases can be found. (list db directory)

- The node directory contains information relating to how andwhere remote instances can be found. (list node directory)

- The Database Connection Services (DCS) Directorycontains information relating to how and where databases onDRDA systems can be found. (list dcs directory)


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3 ways of cataloging a database at a client

Automated configuration using discovery. This method isnormally used to configure small numbers of clients.

- Search discovery- Client searches for servers on the network

- Known discovery- one particular server is queried forinformation about the instances and their databases

Automated configuration using access profiles. Thismethod is used to configure a large number of clients.

- Server profiles- created from DB2 servers, containsinformation about all the instances and databases of server

-Client profiles- used to duplicat the cataloged databasesand/or the client settings from one client to another

Manual configuration used to exploit some advanced optionsnot available using automation

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Get connected using Configuration Assistant

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Configuration Assistant - Search the Network (1)

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Click

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Click

Enter User ID andPassword throughwhich you want toconnect and clickTest Connection

Result tab will showconnection results.

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Configuration Assistant Manually (1)

Enter IP address or

Machine NameDefault port on

Windows : 50000

Click

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Configuration Assistant - Manually (2)

Click

Choose protocol

(e.g. TCP/IP)


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Enter Database name

Click

Enter : Alias of database

which don't exist on client

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Click

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Click

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Click


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Click

Enter User ID andPassword throughwhich you want toconnect and clickTest Connection

Result tab will showconnection results.

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Client/Server Connectivity using CLP

To illustrate connectivity ,we will use a scenario:- INSTANCE is DB2

- DATABASE is SAMPLE

- IP ADDRESS is 9.186.128.141

Settings on the server:

- Value of DB2COMM is tcpip

- Services file contains valid TCP/IP port number , in our case

default is 50000

Windows client machine:

- Catalog the server

- Catalog the database

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CLP - Cataloging the Server and Database

Cataloging a server:

- CATALOG TCPIP NODE db2server

REMOTE 9.186.128.141 SERVER 50000

Cataloging a database:

-CATALOG DATABASE sample AS srv_samp

AT NODE db2server

- UNCATALOG DATABASE sample

Cataloging a DCS database (DRDA Server)

- CATALOG DCS DATABASE test_db AS dsn_db

WITH "DB2 z/OS database"

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Database Objects - Schemas

Schemas are objects that are used to logically classify and

group other objects in the database. Schemas have privileges

associated with them that allow the schema owner to control

which users can create, alter, and drop objects within them.

When an object is created without specifying a schema, object

will be associated with an implicit schema using the

authorization ID.

Most database objects are named using a two-part naming

convention (SCHEMA_NAME.OBJECT_NAME).

The CURRENT SCHEMA special register contains the default

qualifier to be used for unqualified objects.

CREATE SCHEMA inventory


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Database Objects - Tables

A Table is an unordered set of rows. Rows consist of columns.Each column is based on a data type. Types of tables can be:

Base tables: User-defined tables designed to hold persistentuser data, created with the CREATE TABLE SQL statement.

Temporary (Derived) tables: Tables populated with rowsretrieved from one or more base tables in response to a query.

Temporary (Declared) tables: User-defined tables used tohold non-persistent data temporarily, on behalf of a single

application. These tables are explicitly created by anapplication when they are needed and implicitly destroyedwhen the application terminates its last database connection.Declared temporary table is created with the DECLAREGLOBAL TEMPORARY TABLE statement.

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Database Objects - Views

Views can be seen as virtual tables derived from oneor more tables or views and

- Created to limit access to sensitive data while allowingmore general access to other data.

- Views do not contain real data.

- Can be deletable, updatable, insertable, and read-only.

- When changes are made to data through a view, the datais changed in underlying table itself.

-Can be used interchangeably with tables when retrievingdata.

CREATE VIEW dept_view AS

SELECT * FROM department

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Database Objects - Indexes

An index is an object that contains an ordered set of

pointers that refer to rows in a base table, based upon

one or more columns but stored as a separate entity.

Indexes are used to enforce uniqueness in a table

(that is, to make sure that there are no duplicatevalues) and to improve performance when retrieving

information.

Indexes are maintained automatically by DB2 as

data is inserted, updated, and deleted.

CREATE UNIQUE INDEX empno_indx ON

employees(empno)

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Database Objects Aliases & Nicknames

An alias is simply an alternate name for a table or

view.

Like tables and views, an alias can be created,

dropped, and have comments associated with it.

Aliases can also be created for nicknames that refer

to tables or views found on federated systems.

Aliases are publicly referenced names, so no special

authority or privilege is required to use them.

CREATE ALIAS empinfo FOR employees


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Database Objects Sequences

A sequence is an object that is used to generate data valuesautomatically. Unlike an identity column, a sequence is not tied

to any specific column or any specific table.

Values generated can be any exact numeric data type that

has a scale of zero (SMALLINT, BIGINT, INTEGER, or

DECIMAL).The default increment value is 1.

The PREVIOUS VALUE expression returns the most recently

generated value for the specified sequence, while the NEXT

VALUE expression returns the next sequence value.

CREATE SEQUENCE emp_id START WITH 100

INCREMENT BY 10 CACHE 5

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Database Objects Triggers

A trigger is used to define a set of actions that are to beexecuted whenever an insert, update, or delete operation isperformed against a table or updatable view.

Like constraints, triggers are often used to enforce dataintegrity and business rules.

Unlike constraints, triggers can also be used to update othertables, automatically generate or transform values for insertedor updated rows, and invoke functions to perform tasks suchas issuing errors or alerts.

Ex. CREATE TRIGGER pay_raiseBEFORE UPDATE ON employees

FOR EACH ROW

SET new.salary = salary * 1.1

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Database Objects Stored Procedures

An SQL stored procedure is composed entirely of SQL

statements. It is created by executing one form of the CREATE

PROCEDURE SQL statement.

When an SQL stored procedure is used to implement a

business rule, the logic can be incorporated into any

application simply by invoking the stored procedure.

An external stored procedure is a stored procedure that is

written using a high-level programming language such as C,

C++, Java, or COBOL.

External stored procedures can be more powerful than SQL

stored procedures because they can take advantage of system

calls and administrative APIs along with SQL statements.

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Calling a Stored Procedure

CREATE PROCEDURE get_sales(IN quota INTEGER, OUT retcode CHAR(5))DYNAMIC RESULT SETS 1 LANGUAGE SQL

BEGIN

DECLARE sqlstate CHAR(5);

DECLARE sales_results CURSOR WITH RETURN FORSELECT sales_person, SUM(sales) AS total_sales

FROM sales GROUP BY sales_personHAVING SUM(sales) > quota;

DECLARE EXIT HANDLER FOR SQLEXCEPTIONSET retcode = sqlstate; OPEN sales_results;SET retcode = sqlstate;

END

CALL get_sales (25, ?)


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Database Objects Packages

A package is an object that contains information needed to process SQL

statements associated with a source code file of an application program.

During the pre-compile process,

- a source code file containing embedded SQL statements is converted

into a source code file that is made up entirely of high-level programming

language statements.

- At the same time, a corresponding package that contains the access

plans that will be used to process each SQL statement embedded in the

source code file is also produced.

- This package must reside in a DB2 database that contains the data

objects referenced by the package before the corresponding applicationcan be executed against that database.

The process of creating and storing a package in a DB2 database is known

as binding, and by default, packages are automatically bound to a

database during the precompile process.

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Database Objects UDFs

User-defined functions (UDFs) are special objects that areused to extend and enhance the support provided by the built-

in functions available with DB2 9.

Unlike DB2's built-in functions, user-defined functions can take

advantage of system calls and DB2's administrative APIs.

User-defined functions are created (or registered) by executing

the CREATE FUNCTION SQL statement.

SQL Scalar, Table, or Row. constructed using only SQL

statements and can return a value, row or table.External Scalar/Table written using a high-level programming

language such as C, C++, or Java and returns a single value

or table.

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Invoking User-Defined Functions

CREATE FUNCTION jobemployees (job VARCHAR(8))

RETURNS TABLE (empno CHAR(6),

firstname VARCHAR(12), lastname VARCHAR(15))

LANGUAGE SQL READS SQL DATA

NO EXTERNAL ACTION DETERMINISTIC

RETURN SELECT empno, firstnme, lastname

FROM employee

WHERE employee.job = jobemployees.job;

Calling function -

SELECT * FROM TABLE (jobemployees('CLERK'))

SELECT temp AS tempf, convert_temp(temp, 'F') AS tempcFROM climate_info

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5) An alias can be an alternate name for which

two of the following DB2 objects?

-A. Sequence

-B. Trigger

-C. View

-D. Schema

-E. Table

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6) Which of the following DB2 objects can be

referenced by an INSERT statement togenerate values for a column?

A. Sequence

B. Identity column

C. Trigger

D. Table function

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7) Which of the following is NOT an attribute of

Declared Global Temporary Tables (DGTTs)?

A. Each application that defines a DGTT has its own

instance of the DGTT

B. Two different applications cannot create DGTTs

that have the same name

C. DGTTs can only be used by the application that

creates them, and only for the life of the application

D. Data stored in a DGTT can exist across transaction

boundaries

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8) Which of the following is an accurate statement

about packages?

A. Packages provide a logical grouping of database

objects.

B. Packages contain control structures that are

considered the bound form for SQL statements

C. Packages describe the objects in a DB2 database

and their relationship to each other

D. Packages may be used during query optimization

to improve the performance for a subset of SELECT

queries


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9) Which of the following events will NOT cause

a trigger to be activated?

A. A select operation

B. An insert operation

C. An update operation

D. A delete operation

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10) Which of the following DB2 objects is NOT

considered executable using SQL?

A. Routine

B. Function

C. Procedure

D. Trigger

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11) Which of the following is NOT an accurate

statement about views?

A. Views are publicly referenced names and no

special authority or privilege is needed to use them.

B. Views can be used to restrict access to columns in

a base table that contain sensitive data

C. Views can be used to store queries that multiple

applications execute on a regular basis in a database

D. Views support INSTEAD OF triggers

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12) Which of the following SQL statements can be

used to create a DB2 object to store numerical data

as EURO data?

A. CREATE NICKNAME euro FOR DECIMAL (9,3)

B. CREATE ALIAS euro FOR DECIMAL (9,3)

C. CREATE DISTINCT TYPE euro AS DECIMAL

(9,3)

D. CREATE DATA TYPE euro AS DECIMAL (9,3)


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