Hello guys, if you are preparing for Java developer interviews then you may know that the JDBC Interview question forms one of the important sections in Java Interviews.
Similar to multithreading,
Collection
framework and Garbage
collection interview question, JDBC question must be prepared by any Java
programmer. Most of the 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 the frequently asked JDBC Interview questions
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.
If you need more Java questions, you can also buy my book Grokking the Java Interview on Gumroad, its not expensive and covers essential Java interview topics like core java, design patterns, multithreading, collections, JDBC, and more.
11 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 a couple of JDBC questions from practical experience.
Question 1: Difference between SQL Date and java.util.Date in Java? (answer)
Answer: This is one of the JDBC Questions that I like to ask because
knowing how to correctly store and retrieve data in a database is often
confusing for new developers and it's very critical for any application.
The 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 contain both date and time part.
If you want to learn more then you can further see the Complete JDBC Programming Part 1 and 2 courses on Udemy to learn more about JDBC API in depth.
Question 2: What is the benefit of using PreparedStatement in Java?
Answer: Another wonderful JDBC interview question that is very popular
on telephonic as well as on the early rounds of Java Interviews. There are several
benefits of using PreparedStatement while querying databases from Java
programs e.g. better performance and prevents from SQL Injection. I suggest reading 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 a pool of JDBC connection which is used by
applications to query databases.
Since JDBC connection is expensive it takes time
to create them which can slow the response time of the server if created during request
time. Creating them on application start-up and reusing them result in better
performance. See How
to set up JDBC Connection Pool in Java using Spring for more details on the JDBC
connection pool and the benefits it offers.
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.
The key difference between type 2 and type 4 JDBC driver is that you just
need to include the JAR file of the JDBC driver in your classpath to connect the database. See
this link for more differences
between type 2 and type 4 JDBC drivers.
Question 5: What is the difference between java.sql.Time and java.sql.TimeStamp in Java?
Answer: This JDBC question is similar to the earlier JDBC interview
question java.sql.Date vs java.util.Date. The 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 the first column as an integer from the 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 the difference between RowSet and ResultSet in JDBC?
Answer: One of the popular JDBC interviews question nowadays. RowSet extends ResultSet and adds
support for JDBC API to the Java bean component model. The main difference between 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 the benefit of disconnected and connected RowSet.
Question 8: What is use of setAutoCommit(false) in JDBC ?
Answer: This is one of the JDBC Interview questions I touched on Top
10 JDBC best practices for Java programmers. making setAutoCommit(false) saves a
lot of performance as it doesn't commit transactions automatically after each
query and we do batch updates. It allows you to handle it using the commit() and rollback(). This has
resulted in impressive performance gain in the DAO layer.
Question 9: How to call a stored procedure from JDBC in Java?
Answer: This JDBC Interview question is another one you can add to any
frequently asked list and just can't afford to prepare. Mostly asked Java
developers with 2 to 4 years experience. In its simplicity, you can just say
that CallableStatement is used to call a stored procedure, which may lead to questions like how do you pass parameters
to a stored procedure from Java or the difference
between IN and OUT parameters in JDBC, etc.
It's worth preparing this JDBC
question in detail. By the way IN parameter is used to pass input to stored
procedure and the OUT parameter is used to store output return from a stored
procedure.
If your stored procedure returns multiple values then you can also
use ResultSet to traverse all results.
Question 10: What is the difference between Connected and disconnected RowSet in JDBC?
Answer: I have seen this JDBC question asked as a follow-up question of the previous JDBC interview question RowSet vs ResultSet. The main difference between connected and
disconnected RowSet in JDBC is that disconnected RowSet doesn't
require JDBC Connection while it's in a 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 the small
data sets and thin Java clients with a small memory footprint.
Question 11: What is the difference between Statement, PreparedStatement and CallableStatement in Java?
Answer: One of the classical JDBC interview questions. 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 a 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 an important part of any Java interview, let
it a core Java or Java EE 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
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That's all about the frequently asked Java Database interview questions and answers. If you find these JDBC interview questions useful then please share them with your friends and colleagues. If you have any questions or feedback then please drop a note.
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