Using JDBC in Java

Introduction to 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.

The databases that are used in this article

Database software: MySQL5.6

Database: Test

Table: Student, whose table structure is as follows:

+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| ID | Int (11) | NO | PRI |       0 | |
| name | varchar (20) |     YES | |       NULL | |
| 中文版 | float |     YES | |       NULL | |
| Math | float |     YES | |       NULL | |
| Birthday | Date |     YES | |       NULL | |
| Native_place | varchar (30) |     YES | |       NULL | |
| Chinese | Int (11) |     YES | |       NULL | |
+--------------+-------------+------+-----+---------+-------+

| Student | CREATE TABLE ' Student ' (
' id ' int (one) not NULL DEFAULT ' 0 ',
' Name ' varchar (DEFAULT NULL),
' 中文版 ' float DEFAULT NULL,
' Math ' float DEFAULT NULL,
' Birthday ' date DEFAULT NULL,
' Native_place ' varchar (+) DEFAULT NU
' Chinese ' int (one) DEFAULT NULL,
PRIMARY KEY (' id ')
) Engine=innodb DEFAULT Charset=utf8 |

Use of JDBC

• Establish a connection

Establish links in total 3 ways:

1. Static Connection getconnection (String URL)
2. Static Connection getconnection (String URL, Properties info)
3. Static Connection getconnection (string url, string user, string password)

This article will use the 3rd method.

Connection Conn=null;
try {
Conn=drivermanager.getconnection (Url_conn, User_conn, passwd_conn);
} catch (SQLException e) {
E.printstacktrace ();
}

• Get statement

Statement St=null;
try {
St=conn.createstatement ();
} catch (SQLException e) {
E.printstacktrace ();
}

• Execute SQL statement
  • 1-Query
  • 2-Insert
  • 3-Delete
  • 4-Modify

The following is an example of a query:

String sql_query_all_studnet= "SELECT * from student";
ResultSet Res=null;
try {
Res=st.executequery (sql_query_all_studnet);
} catch (SQLException e) {
E.printstacktrace ();
}
try {
SYSTEM.OUT.PRINTLN ("id" + "\ T" + "name" + "\ T" + "Chinese" + "\ T" + "math" + "\ T" + "中文版");
while (Res.next ())
{
int Id=res.getint ("id");
String name=res.getstring ("name");
int Chinese=res.getint ("Chinese");
Double math=res.getdouble ("math");
Double english=res.getdouble ("中文版");
System.out.println (id+ "\ t" +name+ "\ T" +chinese+ "\ T" +math+ "\ T" +english);
}
} catch (SQLException e) {
E.printstacktrace ();
}

Results:

ID name Chinese Math 中文版
1 Pan Yiju 97 91.0 86.0
2 Liu Jingsong 96 68.0 88.0
3 Liu Ji 70 53.0 85.0
4 Li Yanke 96 70.0 85.0
5 Wang Xiaobo 46 79.0 85.0
6 Li Yunxu 97 76.0 79.0
7 Li Jingyao 92 61.0 89.0
8 Gold Relief where 83 43.0 80.0
9 Qin Zi-ai 86 46.0 57.0
10 Guan Yingli 84 77.0 80.0

• Close connection

try {
St.close ();
} catch (SQLException e) {
E.printstacktrace ();
}
try {
Conn.close ();
} catch (SQLException e) {
E.printstacktrace ();
}

Using JDBC in Java