1. Oracle Database Administration
Schema objects 1

2. Schema objects The following types of schema objects exist: Tables
Indexes
Views
Clusters
Synonyms
Sequences
Database links
Materialized views
PL/SQL objects: procedures, functions, packages, object types
Java objects 2

3. Tables Tables are used to store data
Tables can be permanent and temporary
Temporary tables – two types:
data is only stored for a duration of a session
data is only stored for a duration of a transaction
Table data is stored in a data segment in a single tablespace
Table can be a part of a cluster
when using clusters, several tables can be stored together in a single cluster segment 3

4. Tables - examples Permanent table: Temporary table:
CREATE TABLE perm (ID NUMBER);
Temporary table:
CREATE GLOBAL TEMPORARY TABLE temp1
(ID NUMBER) ON COMMIT DELETE ROWS;
CREATE GLOBAL TEMPORARY TABLE temp2 4

5. Tables cont. Tables can be organized: as heap – default
CREATE TABLE as_heap (ID NUMBER);
as index – table data stored together with primary key data
CREATE TABLE as_index
(ID NUMBER PRIMARY KEY,
NAME VARCHAR2(100))
ORGANIZATION INDEX; 5

6. Table columns Oracle supports the following data types:
CHAR – fixed length character data, maximum size: 2000 bytes or characters
VARCHAR2 – variable length character data, maximum length: 4000 bytes or characters, size must be specified
NCHAR – fixed length Unicode data
NVARCHAR2 – variable length Unicode data, size must be specified (max bytes)
NUMBER – number, can include precision and scale 6

7. Table columns
DATE – stores date and time, time is stored with a precision up to a second
TIMESTAMP – contains date and time, time is stored with a precision up to fraction of a second
TIMESTAMP WITH TIME ZONE – same as TIMESTAMP, but time zone information is stored
TIMESTAMP WITH LOCAL TIME ZONE – data is normalized to the database time zone, clients see data in their time zone
INTERVAL DAY TO SECOND – stores time interval 7

8. Table columns
RAW – raw binary data, size is up to 2000 bytes, size is required
LONG RAW – deprecated, BLOB type is recommended instead
ROWID, UROWID – types that store Oracle row identifiers
CLOB – large character data, maximum size over 4GB
BLOB – large binary data
NCLOB – large character data stored as Unicode
BFILE – contains locator to large binary file stored outside of the database 8

9. Table columns
BINARY_FLOAT – 32 bit floating point number, occupies 5 bytes
BINARY_DOUBLE – 64 bit floating point number, occupies 9 bytes 9

10. Character columns Difference between CHAR and VARCHAR2:
CREATE TABLE test (
c CHAR(10),
c VARCHAR2(10));
INSERT INTO test VALUES ('text', 'text');
-- the same as:
INSERT INTO test VALUES ('text ', 'text');
CHAR texts are padded with spaces to the maximum length
VARCHAR2 texts are stored unchanged 10

11. Character column length
Character column length can be specified in bytes or characters:
CREATE TABLE test (
c CHAR(10 CHAR),
c VARCHAR2(10 CHAR),
c CHAR(10 BYTE),
c VARCHAR2(10 BYTE),
c CHAR); -- default to 1 BYTE
Difference between CHAR and BYTE is important when using UTF8 encoding 11

12. Number column Number column can include:
precision – number of significant digits
scale – number of digits after decimal point (can be negative)
if value exceeds precision – error
if values exceeds scale – value is rounded
CREATE TABLE test (
n NUMBER, -- maximum range and precision
n NUMBER(10,2),
n NUMBER(3)) -- same as NUMBER(3,0) 12

13. Number column Value inserted Column specification Stored as
NUMBER(4,2) error
NUMBER(4,-2) 13

14. Date, timestamp
Date columns use client date and time formatting, e.g.:
INSERT INTO test VALUES (' ',
' :30:05');
-- converted by the client before sending to the server
To use date in client independent format, use TO_DATE, TO_CHAR functions:
INSERT INTO test VALUES
(TO_DATE(' ', 'YYYY-MM-DD')
TO_DATE(' :30:05',
'YYYY-MM-DD HH24:MI:SS')
SELECT TO_CHAR(d1, 'YYYY-MM-DD'),
TO_CHAR(d2, 'YYYY-MM-DD HH24:MI:SS') 14

15. Date, timestamp cont. Timestamp columns accept fractional seconds:
CREATE TABLE test (d1 DATE, d2 TIMESTAMP(6));
INSERT INTO test VALUES (SYSDATE, SYSDATE);
SELECT * FROM test;
:16: :16:27,000000
DELETE FROM test;
INSERT INTO test values (SYSTIMESTAMP, SYSTIMESTAMP);
:17: :17:35,076000 15

16. LOB columns LOB columns include:
BLOB – large binary object
CLOB, NCLOB – large text objects
LOBs are stored separate from the rest of the data record
Each LOB column requires two additional segments (possibly in another tablespace) 16

17. Indexes Indexes are used to: Two types of indexes exist in Oracle:
enforce primary key and unique constraints
help validate foreign key constraints
improve performance of queries
Two types of indexes exist in Oracle:
B-Tree indexes (default)
Bitmap indexes
B-Tree indexes can be:
unique
non-unique 17

18. Indexes cont NULL values are ignored by an index (even unique index):
CREATE TABLE test (id NUMBER UNIQUE);
INSERT INTO test VALUES (1);
INSERT INTO test VALUES (1); -- error
INSERT INTO test VALUES (NULL);
INSERT INTO test VALUES (NULL); -- ok
Composite index value is null if all columns are null:
CREATE TABLE test (id1 NUMBER, id2 NUMBER,
UNIQUE(id1, id2));
INSERT INTO test VALUES (1, 1);
INSERT INTO test VALUES (1, 1); -- error
INSERT INTO test VALUES (1, NULL);
INSERT INTO test VALUES (1, NULL); -- error
INSERT INTO test VALUES (NULL, NULL);
INSERT INTO test VALUES (NULL, NULL); -- ok 18

19. Compound indexes
Column values are combined together in the order they appear in CREATE INDEX statement
Statements:
CREATE INDEX IND1 ON EMP(ID, SALARY);
CREATE INDEX IND2 ON EMP(SALARY,ID);
create two different indexes 19

20. Views View is a SQL query definition Views are used to: View security:
simplify complex SQL statements
provide additional security
View security:
It is possible to grant privileges for querying a view, to users that do not have privileges to view the base table(s)
View storage:
view is stored as text SQL definition, no data is stored 20

21. View examples
CREATE TABLE test (id NUMBER UNIQUE, name VARCHAR2(256), description VARCHAR2(4000));
CREATE VIEW test_view AS SELECT id, name FROM test;
GRANT SELECT ON test_view TO some_user;
-- some_user can select data from view test_view,
-- but cannot select data from table test
CREATE VIEW test1_view AS
SELECT sum(salary), dept_id
FROM employees
GROUP BY dept_id
HAVING sum(salary) > 10000 21

22. Updating a view
Some views can be updated. Updating a view causes base table to be updated
Updateable view cannot contain:
Set Operators (INTERSECT, MINUS, UNION, UNION ALL)
DISTINCT
Group Aggregate Functions (AVG, COUNT, MAX, MIN, SUM, etc.)
GROUP BY Clause
ORDER BY Clause
CONNECT BY Clause
START WITH Clause
Collection Expression In A Select List
Subquery In A Select List
Join Query 22

23. Synonyms Synonym is an alias for a schema object Synonyms enable to:
hide the name and owner of the object
move the underlying object without modifying statements that refer to synonyms
Synonyms and security:
synonym is just a simple alias, the privilege to access the underlying object is required (unlike with views) 23

24. Synonyms cont. Synonyms can be public and private Private synonyms:
affect only one user, exist in this user schema, e.g.:
CREATE SYNONYM s1 FOR test1.table1;
SELECT * FROM s1; -- you still need privilege to
-- access test1.table1
Public synonyms
CREATE PUBLIC SYNONYM s1 FOR test1.table1;
-- any user
SELECT * FROM s1; -- the user still needs privilege
-- to access test1.table1
Example: USER_TABLES is a public synonym 24

25. Synonyms cont. To create synonym, user needs:
CREATE SYNONYM or CREATE ANY SYNONYM privilege
CREATE PUBLIC SYNONYM
To drop synonym user needs:
to drop user’s own private synonym - no special privilege
to drop other user’s private synonym - DROP ANY SYNONYM
to drop public synonym - DROP PUBLIC SYNONYM 25

26. Sequences Sequence: Examples: generates sequential numbers
used to generate primary keys
Examples:
sequence with default parameters:
CREATE SEQUENCE seq1;
sequence with non-default parameters
CREATE SEQUENCE seq2
INCREMENT BY 1
START WITH 1
NOMAXVALUE
NOCYCLE
CACHE 10; 26

27. Using sequences Sequences are used to generate primary keys:
It is possible to use:
one sequence for one table
one sequence for a group of tables or for entire application
Sequence behaves like a function, e.g.:
INSERT INTO test1 (date_col) VALUES (SYSDATE);
-- sysdate function used
CREATE SEQUENCE s1;
INSERT INTO test1 (id) VALUES (s1.NEXTVAL);
-- s1.NEXTVAL function used 27

28. The DUAL table Oracle has special DUAL table with one record.
Dual table is useful for getting function values:
SELECT SYSDATE FROM DUAL
-- SYSDATE function computed for every
-- row in DUAL table. Content of DUAL table
–- is ignored, only function value is
-- computed
SELECT s1.NEXTVAL FROM DUAL
-- next sequence value returned for every
-- row in DUAL table 28

29. Nextval and Currval Each sequence has two functions:
nextval - gets next value from a sequence
currval - gets current sequence value (last sequence value returned for current session)
To insert table row using a sequence and find out what was inserted use:
INSERT INTO table1 (id) VALUES (s1.NEXTVAL);
SELECT s1.CURRVAL FROM DUAL; OR
SELECT s1.NEXTVAL FROM DUAL;
INSERT INTO table1 (id)
VALUES (<value from the previous statement>); 29

30. Remaining schema objects
Materialized views - views that cache data, used to improve performance
Database links - for connections between databases, selecting data from remote databases
PL/SQL objects - procedures, functions, packages, object types
Java objects - starting from Oracle 8i it is possible to store Java objects as stored procedures, functions etc. 30

31. Constraints 5 types of contraints: NOT NULL UNIQUE PRIMARY KEY
FOREIGN KEY
CHECK 31

32. NOT NULL constraint Disallows empty (NULL) values in a table column
Single column constraint
In Oracle empty string ('') is considered NULL, empty strings cannot be inserted into columns with NOT NULL constraints 32

33. Unique constraint
Disallows multiple non-NULL values in a table column or set of columns
Multiple NULL values are allowed (NULLs are ignored by unique constraint check)
Can be created on a single column or on a set of columns 33

34. Primary key constraint
Disallows duplicate and null values
There can only be one primary key on a single table
Can be created on a single column or on a set of columns 34

35. Foreign key constraint
Requires each value in a column or set of columns to match a value in related tables's UNIQUE or PRIMARY KEY.
Specifies what should be done if the data in the related table is modified:
default – raise exception
on delete cascade – delete child records
on delete set null – set column value to null 35

36. Foreign key constraint
ALTER TABLE table1 ADD CONSTRAINT FK_1
FOREIGN KEY (col1) REFERENCES table2(id)
ON DELETE CASCADE;
INSERT INTO table2 VALUES (1);
INSERT INTO table1(id, col1) VALUES (1, 1);
INSERT INTO table1(id, col1) VALUES (1, 2); -- error
–- referenced record does not exist in table2
DELETE FROM table2 WHERE id = 1; -- record removed
-- from table1 36

37. Check constraint
Disallows values that do not satisfy the logical expression of the constraint
Example:
ALTER TABLE TABLE1
ADD CONSTRAINT CHK_1
CHECK (column1 IN ('A', 'B', 'C'))
ALTER TABLE EVENTS_TABLE
ADD CONSTRAINT CHK_2
CHECK (start_date < end_date) 37

38. Constraint names Each constraint in Oracle has a name
If name is not provided when the constraint is created, Oracle creates default: 'SYSxxxxx'
Names are useful because:
easier to enable, disable, modify constraints
easier to find constraints in dictionary tables
when exporting and importing data constraint names don’t change 38

39. Constraint names
To specify constraint name create constraints like that:
CREATE TABLE tab1 (
id NUMBER CONSTRAINT pk_tab1 PRIMARY KEY,
col1 VARCHAR2(256) CONSTRAINT unk_tab1 UNIQUE,
col2 VARCHAR2(10) CONSTRAINT chk_tab1
CHECK (col2 in ('A', 'AB', 'ABC')),
CONSTRAINT chk_tab2
CHECK (length(col1) < length(col2)) ); 39

40. Deferred constraints Constraints can be:
immediate – checked at the end of each DML statement
deferred – checked when the transaction is committed
By default constraints are immediate – validated after each statement
Session can request constraints to be deferred:
SET CONSTRAINTS ALL DEFERRED
Deferred mode is ended with:
SET CONSTRAINTS ALL IMMEDIATE
COMMIT 40

41. Deferred constraints Example:
create table table1 (id number primary key);
create table table2 (id number primary key,
col1 number references table1 deferrable);
set constraints all deferred;
insert into table2 values(1, 1);
insert into table1 values(1);
commit; -- ok
insert into table2 values(2, 2);
commit; -- error
set constraints all immediate; -- error 41

42. Constraint states Constraint can be in one of the following states:
ENABLE VALIDATE (same as ENABLE) – constraint is true for all rows in the table
ENABLE NOVALIDATE – checked for new or modified rows
DISABLE NOVALIDATE (same as DISABLE) – constraint not checked, ignored
DISABLE VALIDATE – constraint not checked, but disallows modifications to the constrained rows 42

43. Enabling, disabling constraints
alter table table2 enable novalidate primary key;
Constraint that is enabled novalidate:
new data is checked against the constraint
old data is not checked, some values in the table can violate the constraint 43

44. Security and privileges
Two types of privileges:
system privileges - privilege to perform some action, e.g. create table, drop user, alter index etc.
when the database is created, user SYS is granted all system privileges
object privileges - privilege to access some object in some user’s schema, e.g. insert data into table, select value from a sequence, execute procedure etc.
when the object is created, no object privileges are granted. Object owner can always do any action on the object 44

45. Security and privileges
All privileges are granted using the GRANT statement:
GRANT CREATE SESSION TO user1;
GRANT SELECT ON table1 TO user2;
GRANT SELECT ON table1 TO PUBLIC
GRANT ALL ON table1 TO user2 WITH GRANT OPTION
GRANT CREATE USER TO user1 WITH ADMIN OPTION
Privileges are revoked using the REVOKE statement:
REVOKE CREATE SESSION FROM user1;
REVOKE SELECT ON table1 FROM user2;
REVOKE ALL ON table1 FROM user2; 45

46. System privileges To grant or revoke system privilege:
you must have been granted that privilege with the ADMIN OPTION, or
you must have GRANT ANY PRIVILEGE system privilege 46

47. System privileges Granting system privilege:
GRANT CREATE USER TO user1;
CONNECT user1;
CREATE USER user2 IDENTIFIED BY user2; -- ok
GRANT CREATE USER TO user2; -- error
CONNECT SYSTEM
GRANT CREATE USER TO user1 WITH ADMIN OPTION;
GRANT CREATE USER TO user2; -- ok
GRANT GRANT ANY PRIVILEGE TO user2;
CONNECT user2;
GRANT CREATE USER TO user3 WITH ADMIN OPTION;
REVOKE CREATE USER FROM user3; 47

48. ANY privileges
Special ANY privileges (CREATE ANY xxx, DROP ANY xxx, ALTER ANY xxx) enable access to other user schema:
CREATE ANY xxx - enables creation of objects in other user schema (e.g. CREATE ANY TABLE)
DROP ANY xxx - enables dropping other user’s objects
ALTER ANY xxx - enables modifying other user’s objects 48

49. Object privileges
Object privilege - permission to perform action on a specific schema object
Owner of the object always has all privileges to the owned object, object privileges are granted to other users
Privilege can be granted with GRANT OPTION - grantee can later grant privilege to other users
GRANT SELECT ON table1 TO user1, user2;
GRANT SELECT ON table1 TO user3 WITH GRANT OPTION;
-- user3 can select data from table1 and can
-- grant SELECT privilege to other users 49

50. Revoking object privileges
Example:
owner grants privilege to user1 with grant option
GRANT SELECT ON table1 TO user1 WITH GRANT OPTION;
user1 grants privilege to user2
GRANT SELECT ON table1 TO user2
owner revokes privilege from user1
REVOKE SELECT ON table1 FROM user1
-- privilege is also revoked from user2 50

51. Table privileges Two types of table privileges:
DML (Data Modification Language):
SELECT - permission to select data from a table
UPDATE - permission to update a table, can be granted on specific columns
INSERT - permission to insert rows, can be granted on specific columns
DELETE - permission to delete rows
DDL (Data Definition Language)
INDEX - permission to create index on the table
ALTER - permission to alter the table
REFERENCES - permission to create foreign keys, can be granted on specific columns
ALL – grants all DML and DDL privileges 51

52. Privileges for creating a view
In order to create a view user needs:
create view system privilege or create any view system privilege
explicitly granted object privileges on all base tables not owned by the creator of the view (ability to select data from all base tables), or explicitly granted SELECT ANY TABLE system privilege
to grant other users privilege on a view, base table privileges must be granted with GRANT OPTION
Create view privilege is included in the Resource role 52

53. Privileges for creating a view
CREATE USER test1/test1; GRANT DBA TO test1;
CREATE USER test2/test2; GRANT DBA TO test2;
CONNECT test1/test1;
CREATE TABLE table1 (id NUMBER);
CONNECT test2/test2;
SELECT * FROM test1.table1; -- ok, SELECT ANY DATA
CREATE VIEW test_view AS SELECT * FROM test1.table1;
-- error - insufficient privileges
CONNECT TEST1/TEST1;
GRANT SELECT ON table1 TO test2;
CONNECT TEST2/TEST2;
CREATE VIEW test_view AS SELECT * FROM TEST1.table1;
-- ok, explicitly granted privilege
GRANT SELECT ON test_view TO TEST3;
-- test3 cannot access test_view 53

54. Sequences and procedures
Sequence privileges:
SELECT - permission to select next value from a sequence
ALTER - permission to modify a sequence
GRANT SELECT ON s1 TO user1 WITH GRANT OPTION
Procedure/function/package privilege:
EXECUTE - permission to execute specific procedure
GRANT EXECUTE ON proc1 TO user1 54

55. Roles Roles are used to group privileges Role can contain:
System privileges
Object privileges
Other roles
Predefined roles in every Oracle database:
CONNECT – permissions needed to connect to the database
RESOURCE – permissions needed to create tables, views, sequences in user's own schema
DBA – database administrator privileges 55

56. Roles Role is created using CREATE ROLE statement:
CREATE ROLE role1
Privileges are added to role using GRANT statement:
GRANT CREATE USER TO role1;
GRANT SELECT ON table1 TO role1;
GRANT CONNECT TO role1;
Role is granted using the GRANT statement:
GRANT DBA TO user1;
Role is revoked using the REVOKE statement:
REVOKE DBA FROM user1; 56

57. Granting roles To grant or revoke a role you need:
GRANT ANY ROLE system privilege, or
having the role granted with ADMIN OPTION
Roles can be granted to other roles
To grant privilege to a role the same privileges are required as when granting privilege to a user
Default database roles:
DBA, CONNECT, RESOURCE
EXP_FULL_DATABASE – for exporting
IMP_FULL_DATABASE – for importing
SELECT_CATALOG_ROLE – privileges for reading dictionary views (DBA_ views) 57