数据库查询的几种方法

1、Statement接口查询
这通常是比较常用的。


Statement statement = connection.createStatement();


ResultSet rs = getResultSet("SELECT * FROM TB_STUDENTS WHERE AGE=20");


...


while (rs.next())




...{


...


}

2、PreparedStatement接口查询
如果需要多次执行SQL语句，那么PreparedStatement是首选。因为他包含了一个已经被编译的SQL语句，提高了程序的效率和性能。
下面分别对TB_CUSTOMERS表，进行查询、插入、修改、删除的例子。
查询：


public void preQueryCustomersTB(int ID)




...{


try




...{


PreparedStatement pstmt = connection.prepareStatement("SELECT * FROM TB_CUSTOMERS WHERE ID = ?;");


pstmt.setInt(1, ID);


pstmt.executeQuery();


connection.commit();


pstmt.clearParameters();




} catch (SQLException e)




...{


e.printStackTrace();


}


}

插入：


public boolean preInsertCustomersTB(String company,String name,String address,String email,String phone,String other)




...{


try




...{


PreparedStatement pstmt = connection.prepareStatement("INSERT INTO TB_CUSTOMERS (COMPANY,NAME,ADDRESS,EMAIL,PHONE,OTHER) VALUES (?,?,?,?,?,?) ;");


pstmt.setString(1, company);


pstmt.setString(2, name);


pstmt.setString(3, address);


pstmt.setString(4, email);


pstmt.setString(5, phone);


pstmt.setString(6, other);


pstmt.execute();


connection.commit();




} catch (SQLException e)




...{


// TODO 自动生成 catch 块


e.printStackTrace();


return false;


}


return true;


}

修改：


public boolean preUpdataCustomersTB(int id,String company,String name,String address,String email,String phone,String other)




...{


try




...{


PreparedStatement pstmt = connection.prepareStatement(


"update TB_CUSTOMERS SET company = ?, name = ?, address = ?, email = ?, phone = ?, other = ? WHERE ID = ?;");


pstmt.setString(1, company);


pstmt.setString(2, name);


pstmt.setString(3, address);


pstmt.setString(4, email);


pstmt.setString(5, phone);


pstmt.setString(6, other);


pstmt.setInt(7, id);


pstmt.execute();


connection.commit();




} catch (SQLException e)




...{


// TODO 自动生成 catch 块


e.printStackTrace();


return false;


}


return true;


}

删除：


public void preDeletCustomersTB(int RowID)




...{


try




...{


PreparedStatement pstmt = connection.prepareStatement("delete FROM TB_CUSTOMERS where ID = ?;");


pstmt.setInt(1, RowID);


pstmt.execute();


connection.commit();




} catch (SQLException e)




...{


// TODO 自动生成 catch 块


e.printStackTrace();


}


}

3、CallableStatement接口查询
CallableStatement接口提供了通过JDBC API调用SQL存储过程的标准途径。
使用IN参数的例子：


public void callSetPlayer(String player)




...{


try




...{


CallableStatement cStatement = connection.prepareCall("{CALL setPlayName(?}");


cStatement.setString(1, "John Doe");


cStatement.execute();


} catch (SQLException e)




...{


e.printStackTrace();


}


}

使用OUT参数的例子：


public String callGetPlayer()




...{


try




...{


CallableStatement cStatement = connection.prepareCall("{CALL getPlayName(?}");


cStatement.registerOutParameter(1, java.sql.Types.VARCHAR);


cStatement.execute();


String name = cStatement.getString(1);


//...


return name;


} catch (SQLException e)




...{


e.printStackTrace();


return null;


}


}