Friday, 31 October 2008

JDBC

Four JDBC driver types.

Type 1: JDBC-ODBC Bridge plus ODBC Driver:
The first type of JDBC driver is the JDBC-ODBC Bridge. It is a driver that provides JDBC access to databases through ODBC drivers. The ODBC driver must be configured on the client for the bridge to work. This driver type is commonly used for prototyping or when there is no JDBC driver available for a particular DBMS.

Type 2: Native-API partly-Java Driver:
The Native to API driver converts JDBC commands to DBMS-specific native calls. This is much like the restriction of Type 1 drivers. The client must have some binary code loaded on its machine. These drivers do have an advantage over Type 1 drivers because they interface directly with the database.

Type 3: JDBC-Net Pure Java Driver:
The JDBC-Net drivers are a three-tier solution. This type of driver translates JDBC calls into a database-independent network protocol that is sent to a middleware server. This server then translates this DBMS-independent protocol into a DBMS-specific protocol, which is sent
to a particular database. The results are then routed back through the middleware server and sent back to the client. This type of solution makes it possible to implement a pure Java client. It also makes it possible to swap databases without affecting the client.

Type 4: Native-Protocol Pur Java Driver
These are pure Java drivers that communicate directly with the vendor’s database. They do this by converting JDBC commands directly into the database engine’s native protocol. This driver has no additional translation or middleware layer, which improves performance tremendously.


1. Is there any limitation for no of statments executed with in batchupdate?

No, any number of statements we can write in the batch update but all the updates only means (insert,delete,update) not select

2. What happens when we execute "Class.forname("Driver class name");"

By the end of the execution of Class.forName("Driver
class"); the driver class should be loaded into the memory
but also
1. The driver class should be initialized
2. Should be registered with the driver manager class

The above two operations are not done by forName() . So a pure Static() block is defined in which the above two tasks are manipulated and by which we are able to get connection, immediately after loading the driver class without writing any code to initialize the driver class.


3. What are the Statements in JDBC?

1. Statement: Each time you fire a query it compile and executes and returns the result set
2. PreparedStatement: It parses, compile and optimize the query and keep it, next time when query fired, it picks the compiled query and excute. Also you send dynamic sql statements.
3. Callable Statement: To execute stored procedure like pl/sql



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