java查詢數(shù)據(jù)庫的方法

小編給大家分享一下java查詢數(shù)據(jù)庫的方法，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！

java查詢數(shù)據(jù)庫的方法：首先創(chuàng)建user和teacher數(shù)據(jù)庫；然后將teacher表的【user_id】列與user表的id列建立一對(duì)多連接；接著向user數(shù)據(jù)表中添加數(shù)據(jù)，并按照條件查詢user數(shù)據(jù)庫數(shù)據(jù)；最后根據(jù)主表查詢從表數(shù)據(jù)。

java查詢數(shù)據(jù)庫的方法：

一、創(chuàng)建數(shù)據(jù)庫

創(chuàng)建 user 數(shù)據(jù)庫

創(chuàng)建 teacher 數(shù)據(jù)庫

teacher表的user_id列與user表的id列建立一對(duì)多連接，user_id作為外鍵。

二、Java編程查詢數(shù)據(jù)庫

向user數(shù)據(jù)表中添加數(shù)據(jù)

    /**
     * 添加數(shù)據(jù)
     */
    @Test
    public void addData() {
        Connection connection = null;
        PreparedStatement pstmt =null;
        try {
            connection = JDBCUtils_V3.getConnection();
            String sql = "insert into user values(null,?,?)";
            pstmt = connection.prepareStatement(sql);
            pstmt.setString(1, "wangxuan");
            pstmt.setString(2, "741852");
            int row = pstmt.executeUpdate();
            if (row>0) {
                System.out.println("數(shù)據(jù)添加成功！");
            }else {
                System.out.println("數(shù)據(jù)添加失?。?quot;);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            JDBCUtils_V3.release(connection, pstmt, null);
        }
    }

按照條件查詢user數(shù)據(jù)庫數(shù)據(jù)

    /**
     * 按照條件查詢數(shù)據(jù)
     */
    @Test
    public void selectTest() {
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs =null;
        try {
            conn = JDBCUtils_V3.getConnection();
            String sql = "select * from user where password = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, "123456");
            rs = pstmt.executeQuery();
            while (rs.next()) {
                System.out.println(rs.getString(1)+"----"+rs.getString(2)+"---"+rs.getString(3));
            }
//            System.out.println(rs);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            JDBCUtils_V3.release(conn, pstmt, rs);
        }
    }

一對(duì)多查詢/根據(jù)主表user查詢從表teacher數(shù)據(jù)

    /**
     * 一對(duì)多查詢
     * 根據(jù)主表查詢從表
     */
    @Test
    public void selectOnetoMore() {
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            conn = JDBCUtils_V3.getConnection();
//            String sql = "select * from teacher where user_id = (select id from user where username =?) ";
            String sql = "select * from user,teacher where user.id = teacher.user_id ";
            pstmt = conn.prepareStatement(sql);
//            pstmt.setString(1, "wangxuan");
            rs = pstmt.executeQuery();
            while (rs.next()) {
//                System.out.println(rs.getString(1)+"----"+rs.getString(2)+"---"+rs.getString(3)+"---"+rs.getString(4));
                System.out.println(rs.getString(1)+"----"+rs.getString(2)+"---"+rs.getString(3)+"---"+rs.getString(4)+"----"+rs.getString(5)+"----"+rs.getString(6)+"----"+rs.getString(7));
            }
            System.out.println("查詢完成");
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            JDBCUtils_V3.release(conn, pstmt, rs);
        }
    }

一對(duì)多查詢/根據(jù)從表查詢主表

    /**
     * 一對(duì)多查詢
     * 根據(jù)從表查詢主表數(shù)據(jù)
     */
    @Test
    public void selectMoretoOne() {
        Connection connection = null;
        PreparedStatement pstmtPreparedStatement = null;
        ResultSet rSet =null;
        try {
            connection = JDBCUtils_V3.getConnection();
            String sql = "select * from user where id = (select user_id from teacher where teacher=?)";
            pstmtPreparedStatement = connection.prepareStatement(sql);
            pstmtPreparedStatement.setString(1, "錢田");
            rSet = pstmtPreparedStatement.executeQuery();
            while (rSet.next()) {
                System.out.println(rSet.getString(1)+"----"+rSet.getString(2)+"---"+rSet.getString(3));
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            JDBCUtils_V3.release(connection, pstmtPreparedStatement, rSet);
        }
    }
}

以上是java查詢數(shù)據(jù)庫的方法的所有內(nèi)容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內(nèi)容對(duì)大家有所幫助，如果還想學(xué)習(xí)更多知識(shí)，歡迎關(guān)注億速云行業(yè)資訊頻道！