ORACLE Interview Questions

1.What is an oracle instance?
2.What is a view?
3.What is referential integrity?
4.Name the data dictionary that stores user-defined
constraints?
5.What is a collection of privileges?
6.What is a snapshot?
7.What is a synonym?
8.What is a cursor?
9.What is a sequence?
10.What is a trigger?
11.What is an exception?
12.What is a partition of table?
13.What are pseudo-columns in SQL? Give examples?
14.What are the Data Control statements?
15.What is a schema?
16.What is a type?
17.What is a data model?
18.What is a relation?
19.Advantages of redo log files?
20.What is an Archiver?
21.What is a database buffer cache?
22.What are the 5 background processes in Oracle?
23.%type and %rowtype are attributes for?
24.What are the 2 steps in a two-phase commit?
25.What is a union, intersect, minus?
26.What is a join, explain the types of joins?
27.What is a co-related sub-query?
28.ODBC stands for?
29.Data-type used to work with integers is?
30.Describe data models?
31.Describe the Normalization principles?
32.What are the types of Normalization?
33.What is de-normalization?
SQL SERVER:-
34.What is normalization?
Ans: Well a relational database is basically composed
of tables that contain related data. So the Process of
organizing this data into tables is actually referred
to as normalization.
35.What is a Stored Procedure?
Ans: Its nothing but a set of T-SQL statements
combined to perform a single task of several tasks.
Its basically like a Macro so when you invoke the
Stored procedure, you actually run a set of
statements.
36.Can you give an example of Stored Procedure?
Ans: sp_helpdb , sp_who2, sp_renamedb are a set of
system defined stored procedures. We can also have
user defined stored procedures which can be called in
similar wayWhat is a trigger?
Ans: Triggers are basically used to implement business
rules. Triggers is also similar to stored procedures.
The difference is that it can be activated when data
is added or edited or deleted from a table in a
database.
37.What is a view?
Ans: If we have several tables in a db and we want to
view only specific columns from specific tables we can
go for views. It would also suffice the needs of
security some times allowing specfic users to see only
specific columns based on the permission that we can
configure on the view. Views also reduce the effort
that is required for writing queries to access
specific columns every time.
38.What is an Index?
Ans: When queries are run against a db, an index on
that db basically helps in the way the data is sorted
to process the query for faster and data retrievals
are much faster when we have an index.
39.What are the types of indexes available with SQL
Server?
Ans: There are basically two types of indexes that we
use with the SQL Server. Clustered and the
Non-Clustered.
40.What is the basic difference between clustered and
a non-clustered index?
Ans: The difference is that, Clustered index is unique
for any given table and we can have only one clustered
index on a table. The leaf level of a clustered index
is the actual data and the data is resorted in case of
clustered index. Whereas in case of non-clustered
index the leaf level is actually a pointer to the data
in rows so we can have as many non-clustered indexes
as we can on the db.
41.What are cursors?
Ans: Well cursors help us to do an operation on a set
of data that we retreive by commands such as Select
columns from table. For example : If we have duplicate
records in a table we can remove it by declaring a
cursor which would check the records during retreival
one by one and remove rows which have duplicate
values.
42.When do we use the UPDATE_STATISTICS command?
Ans: This command is basically used when we do a large
processing of data. If we do a large amount of
deletions any modification or Bulk Copy into the
tables, we need to basically update the indexes to
take these changes into account. UPDATE_STATISTICS
updates the indexes on these tables accordingly.
43.SQL Server runs on which TCP/IP port?
Ans: SQL Server runs on port 1433 but we can also
change it for better security.
44.From where can you change the default port?
Ans: From the Network Utility TCP/IP properties -->
Port number.both on client and the server.
45.Can you tell me the difference between DELETE &
TRUNCATE commands?
Ans: Delete command removes the rows from a table
based on the condition that we provide with a WHERE
clause. Truncate will actually remove all the rows
from a table and there will be no data in the table
after we run the truncate command.
46.Can we use Truncate command on a table which is
referenced by FOREIGN KEY?
Ans: No. We cannot use Truncate command on a table
with Foreign Key because of referential integrity.
47.What is the use of DBCC commands?
Ans: DBCC stands for database consistency checker. We
use these commands to check the consistency of the
databases, i.e., maintenance, validation task and
status checks.
48.Can you give me some DBCC command options?(Database
consistency check)
Ans: DBCC CHECKDB - Ensures that tables in the db and
the indexes are correctly linked.and DBCC CHECKALLOC -
To check that all pages in a db are correctly
allocated. DBCC SQLPERF - It gives report on current
usage of transaction log in percentage. DBCC
CHECKFILEGROUP - Checks all tables file group for any
damage.
49.What command do we use to rename a db?
Ans: sp_renamedb 'oldname' , 'newname'
50.Well sometimes sp_reanmedb may not work you know
because if some one is using the db it will not accept
this command so what do you think you can do in such
cases?
Ans: In such cases we can first bring to db to single
user using sp_dboptions and then we can rename that db
and then we can rerun the sp_dboptions command to
remove the single user mode.
51.What is the difference between a HAVING CLAUSE and
a WHERE CLAUSE?
Ans: Having Clause is basically used only with the
GROUP BY function in a query. WHERE Clause is applied
to each row before they are part of the GROUP BY
function in a query.
52.What do you mean by COLLATION?
Ans: Collation is basically the sort order. There are
three types of sort order Dictionary case sensitive,
Dictonary - case insensitive and Binary.
53.What is a Join in SQL Server?
Ans: Join actually puts data from two or more tables
into a single result set.
54.Can you explain the types of Joins that we can have
with Sql Server?
Ans: There are three types of joins: Inner Join, Outer
Join, Cross Join
55.When do you use SQL Profiler?
Ans: SQL Profiler utility allows us to basically track
connections to the SQL Server and also determine
activities such as which SQL Scripts are running,
failed jobs etc..
56.What is a Linked Server?
Ans: Linked Servers is a concept in SQL Server by
which we can add other SQL Server to a Group and query
both the SQL Server dbs using T-SQL Statements.
57.Can you link only other SQL Servers or any database
servers such as Oracle etc..
Ans: We can link any server provided we have the
OLE-DB provider from Microsoft to allow a link. For
Oracle we have a OLE-DB provider for oracle that
microsoft provides to add it as a linked server to the
sql server group.
58.Which stored procedure will you be running to add a
linked server?
Ans: sp_addlinkedserver, sp_addlinkedsrvlogin
59.What are the OS services that the SQL Server
installation adds?
Ans: MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC
(Distribution transac co-ordinator)
60.Can you explain the role of each service?
Ans: SQL SERVER - is for running the databases
SQL AGENT - is for automation such as Jobs, DB
Maintanance, Backups
DTC - Is for linking and connecting to other SQL
Servers
61.How do you troubleshoot SQL Server if its running
very slow?
Ans: First check the processor and memory usage to see
that processor is not above 80% utilization and memory
not above 40-45% utilization then check the disk
utilization using Performance Monitor, Secondly, use
SQL Profiler to check for the users and current SQL
activities and jobs running which might be a problem.
Third would be to run UPDATE_STATISTICS command to
update the indexes
62.Lets say due to N/W or Security issues client is
not able to connect to server or vice versa. How do
you troubleshoot?
Ans: First I will look to ensure that port settings
are proper on server and client Network utility for
connections. ODBC is properly configured at client end
for connection ------Makepipe & readpipe are utilities
to check for connection. Makepipe is run on Server and
readpipe on client to check for any connection issues.
63.What are the authentication modes in SQL Server?
Ans: Windows mode and mixed mode (SQL & Windows).
64.Where do you think the users names and passwords
will be stored in sql server?
Ans: They get stored in master db in the sysxlogins
table.
65.What is log shipping? Can we do logshipping with
SQL Server 7.0
Ans: Logshipping is a new feature of SQL Server 2000.
We should have two SQL Server - Enterprise Editions.
From Enterprise Manager we can configure the
logshipping. In logshipping the transactional log file
from one server is automatically updated into the
backup database on the other server. If one server
fails, the other server will have the same db and we
can use this as the DR (disaster recovery) plan.
66.Let us say the SQL Server crashed and you are
rebuilding the databases including the master database
what procedure to you follow?
Ans: For restoring the master db we have to stop the
SQL Server first and then from command line we can
type SQLSERVER –m which will basically bring it into
the maintenance mode after which we can restore the
master db.
67.Let us say master db itself has no backup. Now you
have to rebuild the db so what kind of action do you
take?
Ans: (I am not sure- but I think we have a command to
do it).
68.What is BCP? When do we use it?
Ans:BulkCopy is a tool used to copy huge amount of
data from tables and views. But it won't copy the
structures of the same.
69.What should we do to copy the tables, schema and
views from one SQL Server to another?
Ans:We have to write some DTS packages for it.

70.What are the different types of joins and what dies
each do?
71.What are the four main query statements?
72.What is a sub-query? When would you use one?
73.What is a NOLOCK?
74.What are three SQL keywords used to change or set
someone’s permissions?
75.What is the difference between HAVING clause and
the WHERE clause?
76.What is referential integrity? What are the
advantages of it?
77.What is database normalization?
78.Which command using Query Analyzer will give you
the version of SQL server and operating system?
79.Using query analyzer, name 3 ways you can get an
accurate count of the number of records in a table?
80.What is the purpose of using COLLATE in a query?
81.What is a trigger?
82.What is one of the first things you would do to
increase performance of a query? Example “ a query ran
yesterday took 30 seconds, today it takes 6 minutes”
83.What is an execution plan? When would you use it?
How would you view the execution plan?
84.What is the STUFF function and how does it differ
from the REPLACE function?
85.What does it mean to have quoted_identifier on?
What are the implications of having it off?
86.What are the different types of replication? How
are they used?
87.What is the difference between a local and a global
variable?
88.What is the difference between a Local temporary
table and a Global temporary table? How is each one
used?
89.What are cursors? Name four types of cursors and
when each one would be applied?
90.What is the purpose of UPDATE STATISTICS?
91.How do you use DBCC statements to monitor various
aspects of a SQL server installation?
92.How do you load large data to the SQL server
database?
93.How do you check the performance of a query and how
do you optimize it?
94.How do SQL server 2000 and XML linked? Can XML be
used to access data?
95.What is SQL server agent?
96.What is referential integrity and how is it
achieved?
97.What is indexing?
98.What is normalization and what are the different
forms of normalizations?
99.Difference between server.transfer and
server.execute method?
100.What id de-normalization and when do you do it?
101.What is better- 2nd Normal form or 3rd normal
form? Why?
102.Can we rewrite subqueries into simple select
statements or with joins? Example?
103.What is a function? Give some example?
104.What is a stored procedure?
105.Difference between Function and Procedure-in
general?
106.Difference between Function and Stored Procedure?
107.Can a stored procedure call another stored
procedure. If yes what level and can it be controlled?
108.Can a stored procedure call itself(recursive). If
yes what level and can it be controlled.?
109.How do you find the number of rows in a table?
110.Difference between Cluster and Non-cluster index?
111.What is a table called, if it does not have
neither Cluster nor Non-cluster Index?
112.Explain DBMS, RDBMS?
113.Explain basic SQL queries with SELECT from where
Order By, Group By-Having?
114.Explain the basic concepts of SQL server
architecture?
115.Explain couple pf features of SQL server
2000(Scalability, Availability, Integration with
internet, etc.)?
116.Explain fundamentals of Data ware housing & OLAP?
117.Explain the new features of SQL server 2000?
118.How do we upgrade from SQL Server 6.5 to 7.0 and
7.0 to 2000?
119.What is data integrity? Explain constraints?
120.Explain some DBCC commands?
121.Explain sp_configure commands, set commands?
122.Explain what are db_options used for?
123.What is the basic functions for master, msdb,
tempdb databases?
124.What is a job?
125.What are tasks?
126.What are primary keys and foreign keys?
127.How would you Update the rows which are divisible
by 10, given a set of numbers in column?
128.If a stored procedure is taking a table data type,
how it looks?
129.How m-m relationships are implemented?
130.How do you know which index a table is using?
131.How will oyu test the stored procedure taking two
parameters namely first name and last name returning
full name?
132.How do you find the error, how can you know the
number of rows effected by last SQL statement?
133.How can you get @@error and @@rowcount at the same
time?
134.What are sub-queries? Give example? In which case
sub-queries are not feasible?
135.What are the type of joins? When do we use Outer
and Self joins?
136.Which virtual table does a trigger use?
137.How do you measure the performance of a stored
procedure?
138.Questions regarding Raiseerror?
139.Questions on identity?
140.If there is failure during updation of certain
rows, what will be the state?