Oracle Database Question Bank    ... 6


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SQL PLUS STATEMENTS

1. What are the types of SQL Statement ?
Data Definition Language : CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT.
Data Manipulation Language : INSERT,UPDATE,DELETE,LOCK TABLE,EXPLAIN PLAN & SELECT.
Transactional Control : COMMIT & ROLLBACK
Session Control : ALTERSESSION & SET ROLE
System Control : ALTER SYSTEM.

2. What is a transaction ?
Transaction is logical unit between two commits and commit and rollback.

3. What is difference between TRUNCATE & DELETE ?
TRUNCATE commits after deleting entire table i.e., can not be rolled back. Database triggers do not fire on TRUNCATE
DELETE allows the filtered deletion. Deleted records can be rolled back or committed.
Database triggers fire on DELETE.

4. What is a join ? Explain the different types of joins ?
Join is a query which retrieves related columns or rows from multiple tables.
Self Join - Joining the table with itself.
Equi Join - Joining two tables by equating two common columns.
Non-Equi Join - Joining two tables by equating two common columns.
Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table.

5. What is the Subquery ?
Subquery is a query whose return values are used in filtering conditions of the main query.

6. What is correlated sub-query ?
Correlated sub_query is a sub_query which has reference to the main query.

7. Explain Connect by Prior ?
Retrieves rows in hierarchical order.
e.g. select empno, ename from emp where.

8. Difference between SUBSTR and INSTR ?
INSTR (String1,String2(n,(m)),
INSTR returns the position of the mth occurrence of the string 2 in
string1. The search begins from nth position of string1.
SUBSTR (String1 n,m)
SUBSTR returns a character string of size m in string1, starting from nth position of string1.

9. Explain UNION,MINUS,UNION ALL, INTERSECT ?
INTERSECT returns all distinct rows selected by both queries.
MINUS - returns all distinct rows selected by the first query but not by the second.
UNION - returns all distinct rows selected by either query
UNION ALL - returns all rows selected by either query, including all duplicates.

10. What is ROWID ?
ROWID is a pseudo column attached to each row of a table. It is 18 character long, blockno, rownumber are the components of ROWID.

11. What is the fastest way of accessing a row in a table ?
Using ROWID.

CONSTRAINTS

12. What is an Integrity Constraint ?
Integrity constraint is a rule that restricts values to a column in a table.

13. What is Referential Integrity ?
Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.

14. What are the usage of SAVEPOINTS ?
SAVEPOINTS are used to subdivide a transaction into smaller parts. It enables rolling back part of a transaction. Maximum of five save points are allowed.

15. What is ON DELETE CASCADE ?
When ON DELETE CASCADE is specified ORACLE maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.

16. What are the data types allowed in a table ?
CHAR,VARCHAR2,NUMBER,DATE,RAW,LONG and LONG RAW.

17. What is difference between CHAR and VARCHAR2 ? What is the maximum SIZE allowed for each type ?
CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR it is 255 and 2000 for VARCHAR2.

18. How many LONG columns are allowed in a table ? Is it possible to use LONG columns in WHERE clause or ORDER BY ?

Only one LONG columns is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.

19. What are the pre requisites ?
I. to modify datatype of a column ?
ii. to add a column with NOT NULL constraint ?
To Modify the datatype of a column the column must be empty.
to add a column with NOT NULL constrain, the table must be empty.

20. Where the integrity constraints are stored in Data Dictionary ?
The integrity constraints are stored in USER_CONSTRAINTS.

21. How will you a activate/deactivate integrity constraints ?
The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE constraint/DISABLE constraint.

22. If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE ?
It won't, Because SYSDATE format contains time attached with it.

23. What is a database link ?
Database Link is a named path through which a remote database can be accessed.

24. How to access the current value and next value from a sequence ? Is it possible to access the current value in a session before accessing next value ?
Sequence name CURRVAL, Sequence name NEXTVAL.
It is not possible. Only if you access next value in the session, current value can be accessed.

25. What is CYCLE/NO CYCLE in a Sequence ?
CYCLE specifies that the sequence continues to generate values after reaching either maximum or minimum value. After pan ascending sequence reaches its maximum value, it generates its minimum value. After a descending sequence reaches its minimum, it generates its maximum.

NO CYCLE specifies that the sequence cannot generate more values after reaching its maximum or minimum value.

26. What are the advantages of VIEW ?
To protect some of the columns of a table from other users.
To hide complexity of a query.
To hide complexity of calculations.

27. Can a view be updated/inserted/deleted? If Yes under what conditions ?
A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.

28.If a View on a single base table is manipulated will the changes be reflected on the base table?
If changes are made to the tables which are base tables of a view will the changes be reference on the view.

PACKAGE PROCEDURE & FUNCTION

29. What is a Package Procedure ?
A Package procedure is built in PL/SQL procedure.

30. What are the different types of Package Procedure ?
1. Restricted package procedure.
2. Unrestricted package procedure.

31. What is the difference between restricted and unrestricted package procedure ?
Restricted package procedure that affects the basic basic functions of SQL * Forms. It cannot used in all triggers except key triggers.
Unrestricted package procedure that does not interfere with the basic functions of SQL * Forms it can be used in any triggers.

32. Classify the restricted and unrestricted procedure from the following.
a. Call
b. User-Exit
c. Call-Query
d. Up
e. Execute-Query
f. Message
g. Exit-From
h. Post
i. Break

a. Call - unrestricted
b. User Exit - Unrestricted
c. Call_query - Unrestricted
d. Up - Restricted
e. Execute Query - Restricted
f. Message - Restricted
g. Exit_form - Restricted
h. Post - Restricted
i. Break - Unrestricted.

33. Can we use a restricted package procedure in ON-VALIDATE-FIELD Trigger ?
No.

34. What SYNCHRONIZE procedure does ?
It synchronizes the terminal screen with the internal state of the form.

35. What are the unrestricted procedures used to change the popup screen position during run time ?
Anchor-view
Resize -View
Move-View.

36. What Enter package procedure does ?
Enter Validate-data in the current validation unit.

37. What ERASE package procedure does ?
Erase removes an indicated global variable.

38. What is the difference between NAME_IN and COPY ?
Copy is package procedure and writes values into a field.
Name in is a package function and returns the contents of the variable to which you apply.

38. Identify package function from the following ?
1. Error-Code
2. Break
3. Call
4. Error-text
5. Form-failure
6. Form-fatal
7. Execute-query
8. Anchor_View
9. Message_code


1. Error_Code
2. Error_Text
3. Form_Failure
4. Form_Fatal
5. Message_Code

40. How does the command POST differs from COMMIT ?
Post writes data in the form to the database but does not perform database commit
Commit permanently writes data in the form to the database.

41. What the PAUSE package procedure does ?
Pause suspends processing until the operator presses a function key

42. What package procedure is used for calling another form ?
Call (E.g. Call(formname)

43. What package procedure used for invoke sql *plus from sql *forms ?
Host (E.g. Host (sqlplus))

44. Error_Code is a package procedure ?
a. True b. false
False.

45. EXIT_FORM is a restricted package procedure ?
a. True b. False
True.

46. When the form is running in DEBUG mode, If you want to examine the values of global variables and other form variables, What package procedure command you would use in your trigger text ?
Break.

SYSTEM VARIABLES

47. List the system variables related in Block and Field?
1. System.block_status
2. System.current_block
3. System.current_field
4. System.current_value
5. System.cursor_block
6. System.cursor_field
7. System.field_status.

48. What is the difference between system.current_field and system.cursor_field ?
1. System.current_field gives name of the field.
2. System.cursor_field gives name of the field with block name.

49. The value recorded in system.last_record variable is of type
a. Number
b. Boolean
c. Character.
b. Boolean.

50. What is an User Exits ?
A user exit is a subroutine which are written in programming languages using pro*C pro *Cobol , etc., that link into the SQL * forms executable.

51. What are the type of User Exits ?
ORACLE Precompliers user exits
OCI (ORACLE Call Interface)
Non-ORACEL user exits.

52. What do you mean by a page ?
Pages are collection of display information, such as constant text and graphics.

53. How many pages you can in a single form ?
Unlimited.

54. Two popup pages can appear on the screen at a time ?
a. True b. False
a. True.

55.What is the significance of PAGE 0 in forms 3.0 ?
Hide the fields for internal calculation.

56. Deleting a page removes information about all the fields in that page ?
a. True. b. False
a. True.

57. What do you mean by a pop-up window ?
Pop-up windows are screen areas that overlay all or a portion of the
display screen when a form is running.

58. What are the types of Pop-up window ?
the pop-up field editor
pop-up list of values
pop-up pages.

59. What is an Alert ?
An alert is window that appears in the middle of the screen overlaying a portion of the current display.