如何对 JDBC 的表格内容进行排序？
对表的内容进行排序意味着以有组织的方式重新排列记录，以使数据更有用。您可以通过在表中选择一列来对表中的所有记录进行排序，根据该列对数据进行排序。简单地说，当你对数据排序时，你按照逻辑顺序排列数据。
- And text and numbers can be sorted in any order, that is, ascending or descending.
- One or more columns can be sorted at the same time.
- In SQL, the order by clause is used to sort the table contents in JDBC .
- By default, some databases sort queries in ascending order. But we can also sort in descending order.
- We can use the ORDER BY clause for one or more columns at the same time.
后续步骤:
- Import the necessary libraries.
- Register driver class
- Connect to your database by providing an address, user name and password.
- Create your statement
- Write your query.
- Execute your query and store the results in the result set.
- Show results
How ORDER BY works:
query -----> select * from Table_Name ORDER BY Column1,Column 2;
user table -----> --------------------------------------------------
|| id || Name || Age ||
|| 1 || Prateek || 20 ||
|| 4 || Chhavi || 21 ||
|| 3 || Aman || 22 ||
|| 2 || Kartikay || 22 ||
|| 5 || Prakhar || 20 ||
--------------------------------------------------
Example 1: select * from user ORDER BY id;
Output: --------------------------------------------------
|| id || Name || Age ||
|| 1 || Prateek || 20 ||
|| 2 || Kartikay || 22 ||
|| 3 || Aman || 22 ||
|| 4 || Chhavi || 21 ||
|| 5 || Prakhar || 20 ||
--------------------------------------------------
Example 2: select * from user ORDER BY name,age;
Output: --------------------------------------------------
|| id || Name || Age ||
|| 3 || Aman || 22 ||
|| 4 || Chhavi || 21 ||
|| 2 || Kartikay || 22 ||
|| 5 || Prakhar || 20 ||
|| 1 || Prateek || 20 ||
--------------------------------------------------
例 1:
爪哇
// Java program to sort contents of a table
import java.sql.*;
public class GFG {
// driver code
public static void main(String[] args) throws Exception
{
// Register Driver Class
Class.forName("org.apache.derby.jdbc.ClientDriver");
// Connection to your database, pass all the
// necessary parameters such as address , username &
// password
Connection con = DriverManager.getConnection();
// Create Statement
Statement stmt = con.createStatement();
// Query to be executed
String query = "Select * from users ORDER by id";
// Execute SQL query and store the result in any
// variable
ResultSet rs = stmt.executeQuery(query);
System.out.println("Id Name Age");
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
System.out.println(id + " " + name + " "
+ age);
}
// close the connection
con.close();
}
}
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