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ORACLE interview questions for database administration
1.What is
normalization? - 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.
2.What is a
Stored Procedure? - 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.
3.Can you give an example of Stored Procedure? - 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 way.
4.What is a trigger? - 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.
5.What is a view? - 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.
6.What is an Index? - 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.
7.What are the types of indexes available with SQL Server? -
There are basically two types of indexes that we use with
the SQL Server. Clustered and the Non-Clustered.
8.What is the basic difference between clustered and a
non-clustered index? - 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.
9.What are cursors? - 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.
10.When do we use the UPDATE_STATISTICS command? - 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.
11.Which TCP/IP port does SQL Server run on? - SQL Server
runs on port 1433 but we can also change it for better
security.
12.From where can you change the default port? - From the
Network Utility TCP/IP properties –> Port number.both on
client and the server.
13.Can you tell me the difference between DELETE & TRUNCATE
commands? - 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.
14.Can we use Truncate command on a table which is
referenced by FOREIGN KEY? - No. We cannot use Truncate
command on a table with Foreign Key because of referential
integrity.
15.What is the use of DBCC commands? - 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.
16.Can you give me some DBCC command options?(Database
consistency check) - 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 - 17.It gives report on current
usage of transaction log in percentage. DBCC CHECKFILEGROUP
- Checks all tables file group for any damage.
18.What command do we use to rename a db? - sp_renamedb
‘oldname’ , ‘newname’
19.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? - 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.
20.What is the difference between a HAVING CLAUSE and a
WHERE CLAUSE? - 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.
21.What do you mean by COLLATION? - Collation is basically
the sort order. There are three types of sort order
Dictionary case sensitive, Dictonary - case insensitive and
Binary.
22.What is a Join in SQL Server? - Join actually puts data
from two or more tables into a single result set.
23.Can you explain the types of Joins that we can have with
Sql Server? - There are three types of joins: Inner Join,
Outer Join, Cross Join
24.When do you use SQL Profiler? - 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..
25.What is a Linked Server? - 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.
26.Can you link only other SQL Servers or any database
servers such as Oracle? - 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.
27.Which stored procedure will you be running to add a
linked server? - sp_addlinkedserver, sp_addlinkedsrvlogin
28.What are the OS services that the SQL Server installation
adds? - MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC
(Distribution transac co-ordinator)
29.Can you explain the role of each service? - 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
30.How do you troubleshoot SQL Server if its running very
slow? - 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
31.Lets say due to N/W or Security issues client is not able
to connect to server or vice versa. How do you troubleshoot?
- 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.
32.What are the authentication modes in SQL Server? -
Windows mode and mixed mode (SQL & Windows).
33.Where do you think the users names and passwords will be
stored in sql server? - They get stored in master db in the
sysxlogins table.
34.What is log shipping? Can we do logshipping with SQL
Server 7.0 - 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.
35.Let us say the SQL Server crashed and you are rebuilding
the databases including the master database what procedure
to you follow? - 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.
36.Let us say master db itself has no backup. Now you have
to rebuild the db so what kind of action do you take? - (I
am not sure- but I think we have a command to do it).
37.What is BCP? When do we use it? - 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.
38.What should we do to copy the tables, schema and views
from one SQL Server to another? - We have to write some DTS
packages for it.
39.What are the different types of joins and what dies each
do?
40.What are the four main query statements?
41.What is a sub-query? When would you use one?
42.What is a NOLOCK?
43.What are three SQL keywords used to change or set
someone’s permissions?
44.What is the difference between HAVING clause and the
WHERE clause?
45.What is referential integrity? What are the advantages of
it?
46.What is database normalization?
47.Which command using Query Analyzer will give you the
version of SQL server and operating system?
48.Using query analyzer, name 3 ways you can get an accurate
count of the number of records in a table?
49.What is the purpose of using COLLATE in a query?
50.What is a trigger?
51.What is one of the first things you would do to increase
performance of a query? For example, a boss tells you that
“a query that ran yesterday took 30 seconds, but today it
takes 6 minutes”
52.What is an execution plan? When would you use it? How
would you view the execution plan?
53.What is the STUFF function and how does it differ from
the REPLACE function?
54.What does it mean to have quoted_identifier on? What are
the implications of having it off?
55.What are the different types of replication? How are they
used?
56.What is the difference between a local and a global
variable?
57.What is the difference between a Local temporary table
and a Global temporary table? How is each one used?
58.What are cursors? Name four types of cursors and when
each one would be applied?
59.What is the purpose of UPDATE STATISTICS?
60.How do you use DBCC statements to monitor various aspects
of a SQL server installation?
61.How do you load large data to the SQL server database?
62.How do you check the performance of a query and how do
you optimize it?
63.How do SQL server 2000 and XML linked? Can XML be used to
access data?
64.What is SQL server agent?
65.What is referential integrity and how is it achieved?
66.What is indexing?
67.What is normalization and what are the different forms of
normalizations?
68.Difference between server.transfer and server.execute
method?
69.What id de-normalization and when do you do it?
70.What is better - 2nd Normal form or 3rd normal form? Why?
71.Can we rewrite subqueries into simple select statements
or with joins? Example?
72.What is a function? Give some example?
73.What is a stored procedure?
74.Difference between Function and Procedure-in general?
75.Difference between Function and Stored Procedure?
76.Can a stored procedure call another stored procedure. If
yes what level and can it be controlled?
77.Can a stored procedure call itself(recursive). If yes
what level and can it be controlled.?
78.How do you find the number of rows in a table?
79.Difference between Cluster and Non-cluster index?
80.What is a table called, if it does not have neither
Cluster nor Non-cluster Index?
81.Explain DBMS, RDBMS?
82.Explain basic SQL queries with SELECT from where Order
By, Group By-Having?
83.Explain the basic concepts of SQL server architecture?
84.Explain couple pf features of SQL server
Scalability, Availability, Integration with internet, etc.)?
85.Explain fundamentals of Data ware housing & OLAP?
86.Explain the new features of SQL server 2000?
87.How do we upgrade from SQL Server 6.5 to 7.0 and 7.0 to
2000?
88.What is data integrity? Explain constraints?
89.Explain some DBCC commands?
90.Explain sp_configure commands, set commands?
91.Explain what are db_options used for?
92.What is the basic functions for master, msdb, tempdb
databases?
93.What is a job?
94.What are tasks?
95.What are primary keys and foreign keys?
96.How would you Update the rows which are divisible by 10,
given a set of numbers in column?
97.If a stored procedure is taking a table data type, how it
looks?
98.How m-m relationships are implemented?
99.How do you know which index a table is using?
100.How will oyu test the stored procedure taking two
parameters namely first name and last name returning full
name?
101.How do you find the error, how can you know the number
of rows effected by last SQL statement?
102.How can you get @@error and @@rowcount at the same time?
103.What are sub-queries? Give example? In which case
sub-queries are not feasible?
104.What are the type of joins? When do we use Outer and
Self joins?
105.Which virtual table does a trigger use?
106.How do you measure the performance of a stored
procedure?
107.Questions regarding Raiseerror?
108.Questions on identity?
109.If there is failure during updation of certain rows,
what will be the state? |
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