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JDBC Interview Questions

16.Which type of JDBC driver is the fastest one?

JDBC Net pure Java driver(Type IV) is the fastest driver because it converts the JDBC calls into vendor specific protocol calls and it directly interacts with the database.


17.Does the JDBC-ODBC Bridge support multiple concurrent open statements per connection?

No. You can open only one Statement object per connection when you are using the JDBC-ODBC Bridge.


18.Which is the right type of driver to use and when?

  • Type I driver is handy for prototyping
  • Type III driver adds security, caching, and connection control
  • Type III and Type IV drivers need no pre-installation

Note: Preferred by 9 out of 10 Java developers: Type IV. Click here to learn more about JDBC drivers.


19.What are the standard isolation levels defined by JDBC?

The values are defined in the class java.sql.Connection and are:

  • TRANSACTION_NONE
  • TRANSACTION_READ_COMMITTED
  • TRANSACTION_READ_UNCOMMITTED
  • TRANSACTION_REPEATABLE_READ
  • TRANSACTION_SERIALIZABLE

Any given database may not support all of these levels.


20.What is resultset ?

The ResultSet represents set of rows retrieved due to query execution.

		ResultSet rs = stmt.executeQuery(sqlQuery);


21.What are the types of resultsets?

The values are defined in the class java.sql.Connection and are:

  • TYPE_FORWARD_ONLY specifies that a resultset is not scrollable, that is, rows within it can be advanced only in the forward direction.
  • TYPE_SCROLL_INSENSITIVE specifies that a resultset is scrollable in either direction but is insensitive to changes committed by other transactions or other statements in the same transaction.
  • TYPE_SCROLL_SENSITIVE specifies that a resultset is scrollable in either direction and is affected by changes committed by other transactions or statements within the same transaction.

Note: A TYPE_FORWARD_ONLY resultset is always insensitive.


22.What’s the difference between TYPE_SCROLL_INSENSITIVE and TYPE_SCROLL_SENSITIVE?

TYPE_SCROLL_INSENSITIVE TYPE_SCROLL_SENSITIVE
An insensitive  resultset is like the snapshot of the data in the database when query was executed. A sensitive resultset does NOT represent a snapshot of data, rather it contains points to those rows which satisfy the query condition.
After we get the resultset the changes made to data are not visible through the resultset, and hence they are known as insensitive. After we obtain the resultset if the data is modified then such modifications are visible through resultset.
Performance not effected with insensitive. Since a trip is made for every ‘get’ operation, the performance drastically get affected.


22.What is rowset?

A RowSet is an object that encapsulates a set of rows from either Java Database Connectivity (JDBC) result sets or tabular data sources like a file or spreadsheet. RowSets support component-based development models like JavaBeans, with a standard set of properties and an event notification mechanism.


24.What are the different types  of RowSet ?

There are two types of RowSet are there. They are:

  • Connected - A connected RowSet object connects to the database once and remains connected until the application terminates.
  • Disconnected - A disconnected RowSet object connects to the database, executes a query to retrieve the data from the database and then closes the connection. A program may change the data in a disconnected RowSet while it is disconnected. Modified data can be updated in the database after a disconnected RowSet reestablishes the connection with the database.


25.What is the need of BatchUpdates?

The BatchUpdates feature allows us to group SQL statements together and send to database server in one single trip.


26.What is a DataSource?

A DataSource object is the representation of a data source in the Java programming language. In basic terms,

  • A DataSource is a facility for storing data.
  • DataSource can be referenced by JNDI.
  • Data Source may point to RDBMS, file System , any DBMS etc..


27.What are the advantages of DataSource?

The few advantages of data source are :

  • An application does not need to hardcode driver information, as it does with the DriverManager.
  • The DataSource implementations can easily change the properties of data sources. For example: There is no need to modify the application code when making changes to the database details.
  • The DataSource facility allows developers to implement a DataSource class to take advantage of features like connection pooling and distributed transactions.

28.What is connection pooling? what is the main advantage of using connection pooling?

A connection pool is a mechanism to reuse connections created. Connection pooling can increase performance dramatically by reusing connections rather than creating a new physical connection each time a connection is requested..

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