下面是我连接到简单服务器和更新信息等的代码。
package mysqltest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class MySQLTest {
static Connection con = null;
static Statement stmt = null;
static ResultSet result = null;
static String url = "jdbc:mysql://localhost:3306/coffeeshop";
static String user = "root";
static String password = "";
public static void main(String[] args) {
// SQL query string
//update specifics
String push1 = "INSERT INTO Coffees"
+ "(CoffeeName, SupplierID, Price, Sales, Total)"
+ "values"
+ "('Colombian', 95, 5.95, 0, 0)";
String push2 = "INSERT INTO Coffees"
+ "(CoffeeName, SupplierID, Price, Sales, Total)"
+ "values"
+ "('French Roast', 27, 6.95, 0, 0),"
+ "('Espresso', 104, 7.95, 0, 0),"
+ "('Colombian Decaf', 95, 16.45, 0, 0),"
+ "('French Roast Decaf', 27, 8.45, 0, 0)";
String push3 = "UPDATE Coffees"
+ "SET SupplierId=12, Total=2"
+ "WHERE CoffeeName='Colombian'";
String push4 = "DELETE FROM Coffees WHERE CoffeeName='Colombian'";
String query = "SELECT * FROM Coffees";
//clear everything first
//push updates
connect();
pushUpdate(push1);
//need to reconnect after update as update closes connection after updates.
connect();
queries(query);
pushUpdate(push2);
connect();
queries(query);
pushUpdate(push3);
connect();
queries(query);
pushUpdate(push4);
connect();
queries(query);
}
public static boolean connect(){
boolean connect;
try{
con = DriverManager.getConnection(url, user, password);
stmt = con.createStatement();
connect = true;
}catch(SQLException ex){
System.out.println("SQLException caught: " + ex.getMessage());
connect = false;
}
return connect;
}
public static void pushUpdate(String push){
try{
stmt.executeUpdate(push);
}catch(SQLException ex){
System.out.println("SQLException caught: " + ex.getMessage());
}
try{
con.close();
stmt.close();
}catch(SQLException ex){
System.out.println("SQLException caught: " + ex.getMessage());
}
}
public static void queries(String query){
try{
result = stmt.executeQuery(query);
System.out.printf("%-10s%-35s%-12s %-9s%-7s%-7s\n",
"CoffeeID", "CoffeeName", "SupplierID", "Price", "Sales", "Total");
while (result.next()) { // loop until the end of the results
int coffeeID = result.getInt("CoffeeID");
String coffeeName = result.getString("CoffeeName");
int supplierID = result.getInt("SupplierID");
double price = result.getDouble("Price");
int sales = result.getInt("Sales");
int total = result.getInt("Total");
System.out.printf("%8d %-35s%10d %7.2f %7d%7d\n", coffeeID, coffeeName, supplierID, price, sales, total);
}
}catch(SQLException ex){
System.out.println("Exception caught: " + ex.getMessage());
}finally {
try {
if (result != null) {
result.close();
}
}catch (SQLException ex){
System.out.println("SQLException caught: " + ex.getMessage());
}
}
}
}
基本上我已经创建了一个表,我根据“推送”更新了该表。推送 1、2 和 4 工作正常,但是 3 抛出此错误...
“SQLException 被捕获:您的 SQL 语法有错误;请检查与您的 MariaDB 服务器版本相对应的手册,以获取在第 1 行的 '=12, Total=2WHERE CoffeeName='Colombian'' 附近使用的正确语法”
好的,所以基本上我已经测试了 push3,因为它是在我的程序中编写的,写入 cmd 提示符并且它工作正常。显然没有使用“+”符号。
空间很重要。这:
"UPDATE Coffees"
+ "SET SupplierId=12, Total=2"
+ "WHERE CoffeeName='Colombian'"
变成这样:
"UPDATE CoffeesSET SupplierId=12, Total=2WHERE CoffeeName='Colombian'"
CoffeesSET
无效且2WHERE
无效,导致整个语句无法解析。在需要的地方添加空格:
"UPDATE Coffees "
+ "SET SupplierId=12, Total=2 "
+ "WHERE CoffeeName='Colombian'"
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