Java JDBC Quiz 1 | JDBC online test, Online practice Test – Java Test

JDBC driver is an interface enabling a Java application to interact with a database. To connect with individual databases, JDBC requires drivers for each database. The JDBC driver gives out the connection to the database and implements the protocol for transferring the query and result between client and database.

Statement encapsulates an SQL statement which is passed to the database to be parsed, compiled, planned and executed.

Type 2 drivers are useful in situations where a type 3 or type 4 driver is not available yet for your database.

JDBC Net pure Java driver(Type 4) is the fastest driver because it converts the JDBC calls into vendor specific protocol calls and it directly interacts with the database.

CallableStatement is used to call stored procedures on the database.

A transaction is a logical unit of work. To complete a logical unit of work, several actions may need to be taken against a database. Transactions are used to provide data integrity, correct application semantics, and a consistent view of data during concurrent access.

Connection Pooling is a technique used for reuse of physical connections and reduced overhead for your application. Connection pooling functionality minimizes expensive operations in the creation and closing of sessions.

First step is to import packages containing the JDBC classes needed for database programming.

TRANSACTION_READ_COMMITTED prevents dirty read in JDBC, connection class.

Prepared statements are more secure because they use bind variables, which can prevent SQL injection attack.

A CallableStatement can return one ResultSet object or multiple ResultSet objects. Multiple ResultSet objects are handled using operations inherited from Statement. To execute a stored procedure “totalstock” in a database server the snippet used is as follows:

CallableStatement clbstmnt = con.prepareCall(“{call totalStock}”); cs.executeQuery();

To have maximum portability, ResultSet objects and update counts should be processed prior to getting the values of output parameters.

Type 4 Driver is a Database-Protocol Driver(Pure Java Driver). Its implementation allows the conversion of JDBC calls directly into a vendor-specific database protocol. They are installed inside JVM or Java Virtual Machine on the client side system. It is better in performance than type 1 and type 2 drivers as it does not have the overhead of conversion of calls into ODBC or database API calls. It doesn’t require to be associated with the software to work. The advantage of type-4 is that it gets completely implemented in Java to achieve platform independence.

PreparedStatement object are used for the ease of calling the methods or for sending SQL statements to the database. It is a special type of statement derived from the more general class, Statement. It reduces the execution time when a statement object needs to be executed many times. JDBC uses methods like:

1) setobject() – The setObject( ) method can insert Java object types into the database, provided that those objects can be converted to standard SQL types.
2) setBlob()
3) setClob()

to store the java objects. PreparedStatement object contains not just a SQL statement, but a precompiled SQL statement.

JDBC API is used to access a database from a Java application. In this case user need to provide the code to register the installed driver with the program. SQL driver manager is used with static registerDriver(). This class provides the basic requirements and methods to assign the JDBC drivers. getConnection() method allows the program to get the connection to run the program. This method takes the following structure:
getConnection(String URL);
Where the URL is of the form:
jdbc:oracle::/@

1)URL
2)UserName – scott
3)Password – tiger

No. The JDBC-ODBC Bridge does not support concurrent access from different threads. The JDBC-ODBC Bridge uses synchronized methods to serialize all of the calls that it makes to ODBC. Multi-threaded Java programs may use the Bridge, but they won’t get the advantages of multi-threading. In addition, deadlocks can occur between locks held in the database and the semaphore used by the Bridge.

Any data type reads and uploaded itself as an array of byte. Byte is an 8-bit signed two’s complement integer which wraps a value used a primitive type byte in an object. Object of type byte consists of a single field whose type is byte. It also provides several methods for converting a byte to a String and a String to a byte, as well as other constants and methods useful when dealing with a byte. It is also useful for saving memory in large arrays.

TimeStamp has the super class as Date which represents a specific instant in time, with millisecond precision. It allows the date to include year, month, day, hour, minute, and second values. It also allowed the formatting and parsing of date strings. The Calendar class is used to convert between dates and time fields and the DateFormat class is used to format and parse date strings. Although the Date class is intended to reflect coordinated universal time (UTC).

JDBC 3.0 provide an updation classes for BLOB, CLOB, ARRAY and REF functions. It fills up smaller areas of missing functionality. The following list outlines the goals and design for the JDBC API in general and the JDBC 3.0 API:
1. It Fit into the J2EE and J2SE platforms
The JDBC API is a constituent technology of the Java platform. The JDBC 3.0 API should be aligned with the overall direction of the Java 2 Enterprise Edition and Java 2 Standard Edition platforms.
2. It is consistent with SQL99
The JDBC API provides programmatic access from applications written in the Java programming language to standard SQL. SQL99 is now a published standard and includes features that are widely supported among DBMS vendors as well as features that only a few vendors support.
3. Consolidate predecessor specifications
This document incorporates content from three prior JDBC specifications to provide a single standalone specification of the JDBC API.
4. It offers vendor-neutral access to common feature

DatabaseMetaData.getMaxConnections – Retrieves the maximum number of concurrent connections to this database that are possible. The interface is implemented by the driver vendors which let the users know the capabilities of a Database Management System (DBMS) in combination with the driver based on JDBCTM technology (“JDBC driver”) that is used with it.

Information is usually returned by methods in the interface and it applies to the capabilities of a particular driver and a particular DBMS which is working together.

PreparedStatement object are used for sending SQL statements to the database. It is a special type of statement derived from the more general class, Statement. If any execution of Statement object needs to be done many times then the PreparedStatement object reduces the time considerably. PreparedStatement uses SQL statements to send the data to DBMS right away after being compiled. It just not contain SQL statement, but a SQL statement that has been precompiled. This means that when the PreparedStatement is executed, the DBMS can just run the PreparedStatement SQL statement without having to compile it first.