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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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Configuration Assistant - Search the Network (2)
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Configuration Assistant - Search the Network (3)
Click
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Configuration Assistant - Search the Network (4)
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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Configuration Assistant Manually (3)
Enter Database name
Click
Enter : Alias of database
which don't exist on client
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Configuration Assistant Manually (4)
Click
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Configuration Assistant - Manually (5)
Click
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Configuration Assistant Manually (6)
Click
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Configuration Assistant - Manually (7)
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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