在本教程將演示如何在JDBC應(yīng)用程序中刪除一個(gè)數(shù)據(jù)庫表。 在執(zhí)行以下示例之前,請(qǐng)確保您已經(jīng)準(zhǔn)備好以下操作:
username
)和密碼(password
)。注意:這是一個(gè)嚴(yán)肅的操作,必須在繼續(xù)刪除表之前作出明確的決定,因?yàn)閯h除表后,表中的所有內(nèi)容都將丟失。
使用JDBC應(yīng)用程序刪除數(shù)據(jù)庫中的表需要以下步驟:
導(dǎo)入包:需要包含包含數(shù)據(jù)庫編程所需的JDBC類的包。 大多數(shù)情況下,使用import java.sql.*
就足夠了。
注冊(cè)JDBC驅(qū)動(dòng)程序:需要初始化驅(qū)動(dòng)程序,以便可以程序中打開數(shù)據(jù)庫的通信通道。
打開連接:需要使用DriverManager.getConnection()
方法來創(chuàng)建一個(gè)Connection
對(duì)象,它表示與數(shù)據(jù)庫服務(wù)器的物理連接。
執(zhí)行查詢:需要使用類型為Statement
的對(duì)象來構(gòu)建和提交SQL語句,以在選擇的數(shù)據(jù)庫中刪除一個(gè)表。
清理環(huán)境:需要明確地關(guān)閉所有數(shù)據(jù)庫資源,而不依賴于JVM的垃圾收集。
復(fù)制以下示例代碼保存到文件:DropTable.java中,然后編譯并運(yùn)行如下 -
//STEP 1. Import required packages
import java.sql.*;
public class DropTable {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/jdbc_db";
// Database credentials
static final String USER = "root";
static final String PASS = "123456";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
//STEP 3: Open a connection
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Connected database successfully...");
//STEP 4: Execute a query
System.out.println("Deleting table in given database...");
stmt = conn.createStatement();
String sql = "DROP TABLE student ";
stmt.executeUpdate(sql);
System.out.println("Table deleted in given database...");
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
conn.close();
}catch(SQLException se){
}// do nothing
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end JDBCExample
編譯上面代碼,如下 -
F:\worksp\jdbc> javac -Djava.ext.dirs=F:\worksp\jdbc\libs DropTable.java
執(zhí)行上面代碼,如下 -
##F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs CreateDatabase
F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs DropTable
Connecting to a selected database...
Thu Jun 01 22:39:01 CST 2017 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
Connected database successfully...
Deleting table in given database...
Table deleted in given database...
Goodbye!
F:\worksp\jdbc>
在執(zhí)行上面語句后,數(shù)據(jù)庫 jdbc_db 中的 student
表將會(huì)被成功地刪除了。