What is difference between java.sql.Time, java.sql.Timestamp and java.sql.Date - JDBC interview Question

Difference between java.sql.Time, java.sql.Timestamp and java.sql.Date  is most common JDBC question appearing on
many core Java interviews. As JDBC
provides three classes java.sql.Date, java.sql.Time and java.sql.Timestamp to
represent date and time and you already have java.util.Date which can
represent both date and time, this question poses lot of confusion among Java
programmer and that’s why this is one of those tricky
Java questions which is tough to answer. It becomes really tough if
differences between them is not understood correctly. We have already seen some
frequently asked or common JDBC questions like why
JDBC has java.sql.Date despite java.util.Date and Why
use PreparedStatement in Java in our last tutorials and we will see
difference between java.sql.Date, java.sql.Time and java.sql.Timestamp in this
article. By the way apart from these JDBC interview questions, if you are
looking to get most from JDBC you can also see 4
JDBC performance tips and 10
JDBC best practices to follow. Those article not only help you to
understand and use JDBC better but also help on interviews. Let’s come back to
difference sql time, timestamp and sql date.

Difference between java.sql.Time, java.sql.Timestamp
and java.sql.Date:

JDBC in Java has three date/time types corresponding to DATE, TIME and
TIMESTAMP type of ANSI SQL. These types are used to convert SQL types into Java
types.

1) First difference on java.sql.Time vs java.sql.Timestamp vs
java.sql.Date is about information they represent :

JDBC TIME or java.sql.Time represent only time information e.g.
hours, minutes and seconds without any date information.

JDBC DATE or java.sql.Date represent only date information
e.g. year, month and day without any time information.

JDBC TIMESTAMP or java.sql.Timestamp  represent both date and
time information including nanosecond details.

2) java.sql.Time and java.sql.Timestamp
extends java.util.Date
class but java.sql.Date is independent.

3) Time information from java.sql.Date and Date
information from java.sql.Time is normalized and may set to zero
in order to confirm ANSI SQL DATE and TIME types.

So difference between Time, Timestamp and Date of SQL package is clear in
terms of what they represent. On contrary java.util.Date also
represent Date and time information but without nanosecond details and
that's why many people prefer to store date as long value (millisecond passed
from epoch January 1, 1970 00:00:00.000 GMT). If you compare to java.sql.Timestamp with equals()
method it will return false as value of nanosecond is unknown.

That's all on difference between java.sql.Date, java.sql.Time and java.sql.Timestamp. All
differences lies on what exactly the represent. This kinds of questions are
worth looking before going to any JDBC interview as time and date are integral
part of any JDBC interview.

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Source:http://javarevisited.blogspot.com/2012/10/difference-between-javasqltime-date-timestamp-jdbc-interview-question.html