JDBC Interview question forms one of the important section in Java Interviews.
Similar to multithreading,
Collection
framework and Garbage
collection interview question, JDBC question must be prepared by any Java
programmer. Most of questions from JDBC or Java database connectivity comes
from API and basic architecture of JDBC which also involves JDBC drivers. A
good understanding of JDBC API along with database basics like transactions
also help to do well in JDBC interviews. I have collected some of frequently asked JDBC Interview question
for quick reference. This will help to revise some important JDBC concepts and
also give a chance to explore JDBC API to newcomers. If you have any other JDBC
interview question, which has been asked to you or friends, and you think it’s
good to share among Java community then please share with us. Let's see my 11
questions from JDBC, not so tough but worth preparing.
12 JDBC Interview Questions with Answers
Here is my list of interview questions from JDBC. This list contains
questions form JDBC drivers, PreparedStatement, CallableStatement, JDBC
Connection pool, SQL Date and Timestamp API, ResultSet and RowSet concepts
and couple of JDBC question from practical experience.Question 1 : Difference between SQL Date and java.util.Date in Java?
Answer : This is one of JDBC Questions which I like to ask, because
knowing how to correctly store and retrieve date in a database is often
confusing for new developers and its very critical for any application. Main
difference between SQL data i.e. java.sql.Date and util
date i.e. java.util.Date is that SQL Date only contains
date part and not time part but util date contains both date and time part. See
SQL
Date vs Util Date in Java for more differences between them.
Question 2: What is the benefit of using PreparedStatement in Java?
Answer : Another wonderful JDBC interview question which is very popular
on telephonic as well as on early round of Java Interviews. There are several
benefits of using PreparedStatement while querying database from Java
program e.g. better performance and prevents from SQL Injection. I suggest to
read Why
use PreparedStatement in Java for more benefits and details on JDBC
PreparedStatement.
Question 3: What is JDBC database Connection Pool? How to setup in Java?
Answer : I have always seen at least one question related to database
connection pool in JDBC Interview e.g. benefit of using JDBC Connection pool.
Well JDBC connection pool maintains pool of JDBC connection which is used by
application to query database. Since JDBC connection are expensive it take time
to create them which can slow response time of server if created during request
time. Creating them on application start-up and reusing them result in better
performance. See How
to setup JDBC Connection Pool in Java using Spring for more details on JDBC
connection pool and benefits it offer.
Question 4: What is the difference between type 2 and type 4 JDBC drivers in Java?
Answer: This JDBC Interview question is as old as Vector
vs ArrayList or Hashtable
vs HashMap. I remember questions about JDBC ODBC drivers asked during
almost every fresher level interview.
Key difference between type 2 and type 4 JDBC driver is that you just
need to include JAR file of JDBC driver in your classpath to connect database. See
this link for more difference
between type 2 and type 4 JDBC drivers.
Question 5: What is difference between java.sql.Time and java.sql.TimeStamp in Java?
Answer : This JDBC questions is similar to earlier JDBC interview
question java.sql.Date vs java.util.Date. Main
difference is that java.sql.Time class doesn't contain any date
information on it while java.sql.TimeStamp contains date information.
See 4
difference between Time and Timestamp in Java JDBC for more differences.
Question 6: What happens if we call resultSet.getInt(0) when Select query result just have one column of integer type?
Answer : This is one of the tricky
Java question which comes from JDBC. you may think that it will return
first column as integer from Query result set but unfortunately it doesn't. It
throws InvalidColumnIndexException in JDBC
because index for getXXX() or setXXX() in JDBC
starts with 1. See How
to fix InvalidColumnIndexException in JDBC for more details on this JDBC
interview question.
Question 7: What is difference between RowSet and ResultSet in JDBC?
Answer : One of the popular JDBC interview question now days. RowSet extends ResultSet and add
support for JDBC API to Java bean component model. Main difference of ResultSet and RowSet is RowSet being connected
and disconnected, which is another follow-up JDBC question. RowSet makes it
easy to use ResultSet but as I said you only like to
use it to get benefit of disconnected and connected RowSet.
Question 8: What is use of setAutoCommit(false) in JDBC ?
Answer : This is one of the JDBC Interview question I touched on Top
10 JDBC best practices for Java programmer. making setAutoCommit(false) saves a
lot of performance as it doesn't commit transaction automatically after each
query and we do batch update. It allows you to handle it using commit() and rollback(). This has
result in impressive performance gain in DAO layer.
Question 9: How to call stored procedure from JDBC in Java?
Answer : This JDBC Interview question is another one you can add on any
frequently asked list and just can't afford not to prepare. Mostly asked to Java
developers with 2 to 4 years experience. In its simplicity you can just say
that CallableStatement is used to call stored procedure, which may lead
questions like how do you pass parameters
to stored procedure from Java or difference
between IN and OUT parameters in JDBC etc. It's worth to prepare this JDBC
question in detail. By the way IN parameter is used to pass input to stored
procedure and OUT parameter is used to store output return from stored
procedure. IF your stored procedure return multiple values than you can also
use ResultSet to traverse all results.
Question 10: What is difference between Connected and disconnected RowSet in JDBC?
Answer : I have seen this JDBC question asked as a follow-up question of
previous JDBC interview question RowSet vs ResultSet. Main difference between connected and
disconnected RowSet in JDBC is that disconnected RowSet doesn't
require JDBC Connection while it's on disconnected state. This makes
disconnected RowSet light and ideal to use in thin
clients, while connected RowSet is just a wrapper around ResultSet. JDBCRowSet and WebRowSet are two
examples of connected RowSet while a CachedRowSet is an
example of disconnected RowSet which caches data in memory. Ideal for small
data set and thin Java clients with small memory foot print.
Question 11: What is difference between Statement, PreparedStatement and CallableStatement in Java?
Answer : One of the classical JDBC interview question. Main difference
between Statement and PreparedSatement is
performance and avoiding SQL Injection as we have seen in Benefits
of using PreparedStatement in Java. While CallableStatement has very specific
use in JDBC and used to call stored procedure from Java program
That's all on these 11 JDBC Interview questions and answers article. As I
said many times, JDBC questions are important part of any Java interview, let
it core Java or J2EE Interview and you just can't ignore it. Always prepare
JDBC well enough to answer any JDBC Interview question to perform well in Java
interviews.
Further Learning
JSP, Servlets and JDBC for Beginners: Build a Database App
Complete JDBC Programming Part 1 and 2
Java Platform: Working with Databases Using JDBC
Related Interview question articles for Java programmer
One JDBC question which I remember is Connection Pool implementation you used e.g. C3PO or DBCP and then comparison between C3PO and DBCP
ReplyDeleteDo enterprises even use straight JDBC anymore? Most projects I've been on in the last 8 years have always used Spring, Hibernate, EJBs, or some other data abstraction layer.
ReplyDeleteEven though JDBC is not part of core java I increasingly see questions from JDBC in core Java interviews. thanks for sharing these, hope you could share some more questions related to performance and security aspect of JDBC.
ReplyDelete