java若依增删改查

Java的增删改查通常是指对数据库中的数据进行操作，需要使用JDBC（Java Database Connectivity）来连接数据库并执行相应的SQL语句，具体如下：

1. 增加数据

使用INSERT语句向数据库中插入新数据，示例代码如下：

String sql = "INSERT INTO table_name (column1, column2, column3) VALUES (?, ?, ?)";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, value1);
statement.setString(2, value2);
statement.setString(3, value3);
int rowsInserted = statement.executeUpdate();
if (rowsInserted > 0) {
    System.out.println("A new row has been inserted.");
}

2. 删除数据

使用DELETE语句从数据库中删除数据，示例代码如下：

String sql = "DELETE FROM table_name WHERE column1 = ?";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, value1);
int rowsDeleted = statement.executeUpdate();
if (rowsDeleted > 0) {
    System.out.println("The row has been deleted.");
}

3. 修改数据

使用UPDATE语句修改数据库中的数据，示例代码如下：

String sql = "UPDATE table_name SET column1 = ? WHERE column2 = ?";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, newValue);
statement.setString(2, criteriaValue);
int rowsUpdated = statement.executeUpdate();
if (rowsUpdated > 0) {
    System.out.println("The row has been updated.");
}

4. 查询数据

使用SELECT语句从数据库中查询数据，示例代码如下：

String sql = "SELECT * FROM table_name WHERE column1 = ?";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, criteriaValue);
ResultSet result = statement.executeQuery();
while (result.next()) {
    String value1 = result.getString("column1");
    String value2 = result.getString("column2");
    String value3 = result.getString("column3");
    System.out.println(value1 + ", " + value2 + ", " + value3);
}