Download Oracle Database 10g: Administration Workshop I

Managing Schema Objects
Copyright © 2005, Oracle. All rights reserved.
Objectives
After completing this lesson, you should be able to do
the following:
• Define schema objects and data types
• Create and modify tables
• Define constraints
• View the columns and contents of a table
• Create indexes
• Create views
• Create sequences
• Delete the data in a table
• Explain the use of temporary tables
6-2
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What Is a Schema?
owns
HR schema
HR user
6-3
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Schemas
Schemas that created as part of the database creation
process are:
• SYS
• SYSTEM
•
6-4
Sample schemas, optionally
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Accessing Schema Objects
6-6
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Naming Database Objects
•
The length of names must be from 1 to 30 bytes,
with these exceptions:
– Names of databases are limited to 8 bytes.
– Names of database links can be as long as 128
bytes.
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•
•
6-7
Nonquoted names cannot be Oracle-reserved
words.
Nonquoted names must begin with an alphabetic
character from your database character set.
Quoted names are not recommended.
Copyright © 2005, Oracle. All rights reserved.
Naming Database Objects
•
Nonquoted names can contain only:
– Alphanumeric characters from your database
character set
– The underscore (_)
– Dollar sign ($)
– Pound sign (#)
•
6-8
No two objects can have the same name within the
same namespace.
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Schema Object Namespaces
The following are in the same
namespace:
Tables
Views
Sequences
Private synonyms
Stand-alone procedures
Stand-alone stored
functions
Packages
Materialized views
User-defined types
6-9
Each of the following have
their own namespace:
Indexes
Constraints
Clusters
Database triggers
Private database links
Dimensions
Copyright © 2005, Oracle. All rights reserved.
Specifying Data Types in Tables
Common data types:
• CHAR(size [BYTE|CHAR]): Fixed-length
character data of size bytes or characters
• VARCHAR2(size [BYTE|CHAR]): Variable-length
character string having a maximum length of size
bytes or characters
• DATE: Valid date range from January 1, 4712 B.C.
through A.D. December 31, 9999
• NUMBER(p,s): Number with precision p and scale
s
6-10
Copyright © 2005, Oracle. All rights reserved.
Other Data Types
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•
6-11
BINARY_FLOAT
BINARY_DOUBLE
FLOAT
INTEGER
NCHAR
NVARCHAR2
LONG
LONG RAW
•
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•
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•
RAW
ROWID
UROWID
BLOB
CLOB
NCLOB
BFILE
TIMESTAMP
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Creating and Modifying Tables
Specify the table
name and schema.
Specify the column names,
data types, and lengths.
6-13
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Understanding Data Integrity
JOB_HISTORY
DEPARTMENTS
LOCATIONS
EMPLOYEE_ID
(PK,FK)
START_DATE (PK)
END_DATE
JOB_ID (FK)
DEPARTMENT_ID (FK)
DEPARTMENT_ID (PK)
DEPARTMENT_NAME
MANAGER_ID
LOCATION_ID (FK)
LOCATION_ID (PK)
STREET_ADDRESS
POSTAL_CODE
CITY
STATE_PROVINCE
COUNTRY_ID (FK)
EMPLOYEES
EMPLOYEE_ID (PK)
FIRST_NAME
LAST_NAME
EMAIL
PHONE_NUMBER
HIRE_DATE
JOB_ID (FK)
SALARY
COMMISION_PCT
MANAGER_ID (FK)
DEPARTMENT_ID (FK)
JOBS
JOB_ID (PK)
JOB_TITLE
MIN_SALARY
MAX_SALARY
COUNTRIES
COUNTRY_ID (PK)
COUNTRY_NAME
REGION_ID (FK)
REGIONS
REGION_ID (PK)
REGION_NAME
6-15
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Constraint States
DISABLE
NOVALIDATE
DISABLE
VALIDATE
ENABLE
NOVALIDATE
ENABLE
VALIDATE
No DML
New data
6-17
Existing data
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Defining Constraints
6-19
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Constraint Checking
Constraints are checked at the time of:
• Statement execution, for non-deferred constraints
• COMMIT, for deferred constraints
Case: DML statement, followed by COMMIT
6-20
1
Nondeferred constraints
checked
2
COMMIT issued
3
Deferred constraints checked
4
COMMIT complete
Copyright © 2005, Oracle. All rights reserved.
Creating Constraints with SQL: Examples
a
ALTER TABLE countries
ADD (UNIQUE(country_name) ENABLE NOVALIDATE);
b
ALTER TABLE employees ADD CONSTRAINT pk PRIMARY KEY
(employee_id)
c
6-21
CREATE TABLE t1 (pk NUMBER PRIMARY KEY, fk NUMBER, c1 NUMBER,
c2 NUMBER,
CONSTRAINT ri FOREIGN KEY (fk) REFERENCES t1,CONSTRAINT ck1
CHECK (pk > 0 and c1 > 0));
Copyright © 2005, Oracle. All rights reserved.
Viewing the Columns in a Table
6-22
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Viewing the Contents of a Table
6-23
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Actions with Tables
6-24
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Dropping a Table
Dropping a table removes:
• Data
DROP TABLE hr.employees PURGE;
• Table structure
• Database triggers
• Corresponding indexes
• Associated object privileges
Optional clauses for the DROP TABLE statement:
• CASCADE CONSTRAINTS: Dependent referential
integrity constraints
• PURGE: No flashback possible
6-25
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Truncating a Table
TRUNCATE TABLE hr.employees;
•
•
6-26
Truncating a table makes its row data unavailable,
and optionally releases used space.
Corresponding indexes are truncated.
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Indexes
… WHERE key = 22
Key
Row
pointer
22
22
Index
6-27
Table
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Types of Indexes
These are several types of index structures available
to you, depending on the need:
• A B-tree index is in the form of a binary tree and is
the default index type.
• A bitmap index has a bitmap for each distinct
value indexed, and each bit position represents a
row that may or may not contain the indexed
value. This is best for low-cardinality columns.
6-28
Copyright © 2005, Oracle. All rights reserved.
B-Tree Index
Index entry
Root
Branch
Index entry header
Leaf
Key column length
Key column value
ROWID
6-29
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Bitmap Indexes
Table
File 3
Block 10
Block 11
Block 12
Index
start
end
key ROWID ROWID
bitmap
<Blue, 10.0.3, 12.8.3, 1000100100010010100>
<Green, 10.0.3, 12.8.3, 0001010000100100000>
<Red, 10.0.3, 12.8.3, 0100000011000001001>
<Yellow, 10.0.3, 12.8.3, 0010001000001000010>
6-31
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Index Options
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6-33
A unique index ensures that every indexed value
is unique.
An index can have its key values stored in
ascending or descending order.
A reverse key index has its key value bytes stored
in reverse order.
A function-based index is an index based on a
function’s return value.
A compressed index has repeated key values
removed.
Copyright © 2005, Oracle. All rights reserved.
Creating Indexes
CREATE INDEX my_index ON
employees(last_name, first_name);
6-34
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What Is a View?
LOCATION table
COUNTRY table
View
CREATE VIEW v AS SELECT location_id, country_name FROM
locations l, countries c
WHERE l.country_id = c.country_id AND c.country_id in
('AU','BR');
6-35
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Creating Views
6-36
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Sequences
A sequence is a mechanism for automatically
generating integers that are guaranteed to be unique.
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
6-37
1000000
999995
999990
999985
999980
999975
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1
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3
4
5
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Sequences
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6-38
A sequence has a name, which is how it is
referenced when the next value is requested.
A sequence is not associated with any particular
table or column.
The order of progression can be ascending or
descending.
The interval between numbers can be of any size.
Sequence values can be cached to improve
performance.
A sequence can cycle when a limit is reached.
Copyright © 2005, Oracle. All rights reserved.
Creating a Sequence
6-39
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Using a Sequence
6-41
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Temporary Tables
A temporary table:
• Provides storage of data that is automatically
cleaned up when the session or transaction ends
• Provides private storage of data for each session
• Is available to all sessions for use without
affecting each other’s private data
6-42
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Temporary Tables
(Notes only slide)
6-43
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Temporary Tables: Considerations
•
Use the GLOBAL TEMPORARY clause to create
temporary tables:
CREATE GLOBAL TEMPORARY TABLE employees_temp
ON COMMIT PRESERVE ROWS
AS SELECT * FROM employees;
•
•
Use the TRUNCATE TABLE command to delete the
contents of the table.
You can create the following on temporary tables:
– Indexes
– Views
– Triggers
6-44
Copyright © 2005, Oracle. All rights reserved.
Summary
In this lesson, you should have learned how to:
• Define schema objects and data types
• Create and modify tables
• Define constraints
• View the columns and contents of a table
• Explain the usage of types of indexes
• Create views
• Create and use sequences
• Delete the data in a table in the most efficient
manner
• Explain the use of temporary tables
6-45
Copyright © 2005, Oracle. All rights reserved.
Practice Overview:
Administering Schema Objects
This practice covers the following topics:
• Creating tables with columns
• Creating constraints:
– Primary key
– Check
– Foreign key
•
6-46
Creating indexes
Copyright © 2005, Oracle. All rights reserved.