J2ee--jdbc

    JDBC (Java Data Base Connectivity,java database connection) is a Java API for executing SQL statements that provides unified access to a variety of relational databases, consisting of a set of classes and interfaces written in the Java language. In short, JDBC can do three things: establish a connection to a database, send an SQL statement, and process the result (which acts like a SqlHelper class in a SQL Server database we used to use).

One, the JDBC driver:

Second, the use of JDBC steps:

1. Registration driver (only once) class.forname ("Com.mysql.jdbc.Driver");

2. Establish a connection (Connection) 1) use DriverManager to get the link, you need to pass in three parameters: the number of data is the URL, user name, password. as follows:
Connection conn = drivermanager.getconnection (URL, user, password);

2) through Connecton Object Creation Statement object, there are three ways of

Createstatement () Creates a basic statement object.

Preparestatement (Stringsql): Creates a precompiled statement object based on the incoming SQL statement.

Preparecall (stringsql): Create CallableStatement objects based on incoming SQL statements

3. Create a statement that executes SQL (Statement) 1) Execute the SQL statement code as follows:

1. statement st = conn.createstatement ();   
2. st.executequery (sql);   
3. PREPAREDSTATEMENT  
4. string sql =  "select * from table_name  Where col_name=? ";   
5. preparedstatement ps =  Conn.preparedstatement (SQL);   
6. ps.setstring (1,  "Col _value ");   
7. ps.executequery ();  

2) Statement execute SQL statement, there are three methods to execute

Execute: Can execute any SQL statement, single more troublesome

Executeupdate: DML, DDL statements can be executed. The execution DML returns the number of rows affected by the SQL statement, and the execution DDL returns 0;

executequery: Only query statements are executed, and ResultSet objects that represent the results of the query are returned after execution.

4. Processing execution Results (RESULTSET)

1. resultset rs = statement.executequery (sql);   
2. while (Rs.next ()) {  
3. Rs.getstring ("Col_name");   
4. rs.getint ("Col_name");   
5. //...   
6. }  

5. Releasing Resources release resultset, Statement,connection.

Summary: Through understanding and analysis, in essence, like ADO, three things are done: Establish a connection with the database, send SQL statements, and process the results.

J2ee--jdbc