UPDATE语句用于更新表中的数据。
Update Data - 语法
以下是UPDATE查询的语法-
ij> UPDATE table_name SET column_name=value, column_name=value, ... WHERE conditions;
WHERE子句可以使用比较运算符,如=,!= 、、 =,以及BETWEEN和LIKE运算符。
Update Data - 命令行示例
假设您在数据库中有一个表Employee,其中包含4条记录,如下所示-
ID |NAME |SALARY |LOCATION ---------------------------------------------------------- 1 |Amit |30000 |Hyderabad 2 |Kalyan |40000 |Vishakhapatnam 3 |Renuka |50000 |Delhi 4 |Learnfk |15000 |Mumbai
以下SQL UPDATE语句更新name为Kaylan的员工的Location和Salary字段。
ij> UPDATE Employees SET Location='Chennai', Salary=43000 WHERE Name = 'Kalyan'; 1 rows inserted/updated/deleted
如果获得Employees表的内容,则可以观察到UPDATE查询所做的更改。
ij> select * from Employees; ID |NAME |SALARY |LOCATION ---------------------------------------------------------- 1 |Amit |30000 |Hyderabad 2 |Kalyan |43000 |Chennai 3 |Renuka |50000 |Delhi 4 |Learnfk |15000 |Mumbai 4 rows selected
Update Data - JDBC示例
以下JDBC示例演示了如何使用JDBC程序更新Apache Derby中表的现有记录,在这里,无涯教程使用嵌入式驱动程序连接到名为sampleDB的数据库(如果不存在则创建)。
import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class UpdateData { public static void main(String args[]) throws Exception { //注册驱动 Class.forName("org.apache.derby.jdbc.EmbeddedDriver"); //创建连接 String URL="jdbc:derby:sampleDB;create=true"; Connection conn=DriverManager.getConnection(URL); //获取Statement对象 Statement stmt=conn.createStatement(); //创建表结构,同时写入数据 String query="CREATE TABLE Employees(" + "Id INT NOT NULL GENERATED ALWAYS AS IDENTITY, " + "Name VARCHAR(255), Salary INT NOT NULL, " + "Location VARCHAR(255), " + "PRIMARY KEY (Id))"; String query="INSERT INTO Employees(" + "Name, Salary, Location) VALUES " + "('Amit', 30000, 'Hyderabad'), " + "('Kalyan', 40000, 'Vishakhapatnam'), " + "('Renuka', 50000, 'Delhi'), " + "('Learnfk', 15000, 'Mumbai'), " + "('Trupthi', 45000, 'Kochin'), " + "('Suchatra', 33000, 'Pune'), " + "('Rahul', 39000, 'Lucknow'), " + "('Trupti', 45000, 'Kochin')"; //执行SQL语句 String query="UPDATE Employees SET Location='Chennai', Salary=43000 WHERE Name='Kalyan'"; int num=stmt.executeUpdate(query); System.out.println("Number of records updated are: "+num); } }
在执行上述程序时,您将获得以下输出-
Number of records updated are: 1