Two-tier model is a Java applet applications interact directly with the database. This type of model is referred to as client sever configuration where user is the client and machine that has the database is called as the server.
In this model middle tier is introduced, which is used for various purpose, there are some of the function are used in middle tier, they are
Structured query language is the standard language used to access relational databases. Unfortunately there are no standards set at present for it. JDBC defines a set of generic SQL type identifiers in the class Java.SQL.Types
JDBC deals with some of the performing SQL conformance, they are
Different Types of Driver Managers
JDBC contains three components: application, driver manager and driver. The user application invokes JDBC methods to send SQL statements to the database and retrieves result. JDBC driver manager is used to connect java application to the correct JDBC driver. There are four types of JDBC driver. They are