我已经尝试过堆栈溢出的解决方案，但它没有解决我的问题，所以我想问一下
import java.*;
import java.lang.*;
import java.sql.*;
import java.io.*;
import java.util.*;
public class mysql1
{
static final String url = "jdbc:mysql://localhost:3306/test";
static final String usr = "root";
static final String passwd = "";
public static void main(String [] ar)
{
Connection con = null;
// boolean flag = True;
int ch;
String y;
try
{
System.out.println("connecting to db...\n");
con = DriverManager.getConnection(url,usr,passwd);
System.out.println("Database Connected.\n");
CallableStatement cs = null;
Statement stmnt = con.createStatement();
do
{
Scanner in = new Scanner(System.in);
System.out.println("1.Create Table\n");
System.out.println("2.Insert Table\n");
System.out.println("3.Display Table\n");
System.out.println("4.Update Table\n");
System.out.println("5.Delete Table\n");
System.out.println("6.Creating index\n");
System.out.println("7.Show index\n");
System.out.println("8.Create View\n");
System.out.println("9.Show view\n");
System.out.println("10. Inner Join\n");
System.out.println("11. Right outer join\n");
System.out.println("12. Left outer join\n");
System.out.println("13. Cross join\n");
System.out.println("14. Exit\n");
System.out.println("Enter your choice");
ch = in.nextInt();
switch(ch)
{
case 1:
System.out.println("Creating table 1.\n");
String t1 = "create table employe(id int(10),"+"fname varchar(20),"+"lname varchar(15))";
stmnt.executeUpdate(t1);
System.out.println("Table 1 Created..\n");
System.out.println("Creating table 2.\n");
String t2 = "create table salary(id int(10),"+"fname varchar(20),"+"salray int(10))";
stmnt.executeUpdate(t2);
System.out.println("Table 2 Created..\n");
break;
case 2:
System.out.println("Entering data in 1st table\n");
do
{
System.out.println("Enter id:\n");
int id = in.nextInt();
String str = in.nextLine();
System.out.println("Enter respective fname:\n");
String f = in.nextLine();
System.out.println("Enter lname:\n");
String l = in.nextLine();
PreparedStatement pstmnt = con.preparedStatement("insert into employe values(?,?,?)");
pstmnt = setInt(1,id);
pstmnt = setString(2,f);
pstmnt = setString(3,f);
pstmnt.executeUpdate();
System.out.println("Do you want to continue? y/n");
String ans = in.nextLine();
}while(ans=='y');
System.out.println("Entering data in 2nd table\n");
do
{
System.out.println("Enter id:\n");
int id1 = in.nextInt();
String str1 = in.nextLine();
System.out.println("Enter respective fname:\n");
String f1 = in.nextLine();
System.out.println("Enter the salary\n");
int sal = in.nextInt();
PreparedStatement pstmnt = con.preparedStatement("insert into salary values(?,?,?)");
pstmnt = setInt(1,id);
pstmnt = setString(2,f);
pstmnt = setInt(3,f);
pstmnt.executeUpdate();
System.out.println("Do you want to continue? y/n");
String ans = in.nextLine();
}while(ans=='y');
break;
case 3:
System.out.println("Displaying Table 1.....\n");
String display = "select * from employe";
ResultSet rs1 = stmnt.executeQuery(display);
System.out.println("ID \t FNAME \t LNAME");
while(rs1.next())
{
System.out.println(rs1.getInt(1)+"\t"+rs1.getString(2)+"\t"+rs1.getString(3));
}
System.out.println("Displaying Table 2.....\n");
String display1 = "select * from salary";
ResultSet rs4 = stmnt.executeQuery(display);
System.out.println("ID \t FNAME \t SALARY");
while(rs4.next())
{
System.out.println(rs4.getInt(1)+"\t"+rs4.getString(2)+"\t"+rs4.getInt(3));
}
break;
case 4:
String updat = "update employe set fname=?, lname=? where id=?";
System.out.println("Enter the id of the employe that you want to update:\n");
int id1 = in.nextInt();
System.out.println("Enter new fname:\n");
String f1 = in.nextLine();
System.out.println("Enter new lname:\n");
String l1 = in.nextLine();
PreparedStatement ps = con.preparedStatement(updat);
ps.setString(1,f1);
ps.setString(2,l1);
ps.setInt(3,id1);
ps.executeUpdate();
break;
case 5:
System.out.println("Delete enteries from table using id......\n");
String del = "delete from employe where id=?";
System.out.println("Enter the ID:\n");
int id2 = in.nextInt();
PreparedStatement ps1 = con.PreparedStatement(del);
ps1.setInt(1,id2);
ps.executeUpdate();
break;
case 6:
System.out.println("Creating Index.....\n");
String ind = "create index inde on employe(fname)";
stmnt.executeUpdate(ind);
System.out.println("Index created .....n");
break;
case 7:
System.out.println("Display index.....\n");
String inde = "show index from employe";
ResultSet rs2 = stmnt.executeQuery(inde);
System.out.println(rs2.getString(1)+"\t"+rs2.getString(2)+"\t"+rs2.getString(3)+"\t"+rs2.getString(4)+"\t"+rs2.getString(5)+"\t"+rs2.getString(6)+"\t"+rs2.getString(7)+"\t"+rs2.getString(8)+"\t"+rs2.getString(9)+"\t"+rs2.getString(10)+"\t"+rs2.getString(11)+"\t"+rs2.getString(12)+"\t\n");
break;
case 8:
System.out.println("Create view......\n");
String vew = "create view v1 as select id,lname from employe";
stmnt.executeUpdate(vew);
System.out.println("View created\n");
break;
case 9:
System.out.println("Displaying View......\n");
String disv = "select * from v1";
ResultSet rs3 = stmnt.executeQuery(disv);
while(rs3.next())
{
System.out.println(rs3.getInt(1)+"\t"+rs3.getString(2));
}
break;
case 10:
String inner = "select * from employe e inner join salary sa on e.id=sa.id";
ResultSet rs5 = stmnt.executeQuery(inner);
System.out.println("ID\tFNME\tlname\n");
while(rs5.next())
{
System.out.println(rs5.getInt(1)+"\t"+rs5.getString(2)+"\t"+rs5.getString(3)+"\n");
}
inner1 = "select * from salary sal employe e on sal.id=e.id";
rs5 = stmnt.executeQuery(inner1);
System.out.println("ID\tFNME\tSalary\n");
while(rs5.next())
{
System.out.println(rs5.getInt(1)+"\t"+rs5.getString(2)+"\t"+rs5.getInt(3)+"\n");
}
break;
case 11:
String rj = "select * from employe e right outer join salary s on e.id=s.id";
ResultSet rs6= stmnt.executeQuery(rj);
System.out.println("ID\tFnAME\tLNAME \n");
while(rs6.next())
{
System.out.println(rs6.getInt(1)+"\t"+rs6.getString(2)+"\t"+rs6.getString(3)+"\n");
}
rj = "select * from employe e right outer join salary s on e.id=s.id";
rs6= stmnt.executeQuery(rj);
System.out.println("ID\tFnAME\tLNAME \n");
while(rs6.next())
{
System.out.println(rs6.getInt(1)+"\t"+rs6.getString(2)+"\t"+rs6.getString(3)+"\n");
}
}
System.out.println("Do you want to continue y/n :\n");
y = in.nextLine();
}while(y=="y");
}
catch(SQLException e)
{
System.err.println("Cannot Connect to the db\n");
e.printStackTrace();
}
finally
{
System.out.println("Closing connection.......\n");
if(con!=null)
{
try
{
con.close();
}
catch(SQLException ig)
{}
}
}
}
}
上面的代码仍然缺少一些案例 这是错误
mysql1.java:66: error: cannot find symbol
PreparedStatement pstmnt = con.preparedStatement("insert into employe values(?,?,?)");
^
symbol: method preparedStatement(String)
location: variable con of type Connection
mysql1.java:67: error: cannot find symbol
pstmnt = setInt(1,id);
^
symbol: method setInt(int,int)
location: class mysql1
mysql1.java:68: error: cannot find symbol
pstmnt = setString(2,f);
^
symbol: method setString(int,String)
location: class mysql1
mysql1.java:69: error: cannot find symbol
pstmnt = setString(3,f);
^
symbol: method setString(int,String)
location: class mysql1
mysql1.java:73: error: cannot find symbol
}while(ans=='y');
^
symbol: variable ans
location: class mysql1
mysql1.java:84: error: cannot find symbol
PreparedStatement pstmnt = con.preparedStatement("insert into salary values(?,?,?)");
^
symbol: method preparedStatement(String)
location: variable con of type Connection
mysql1.java:85: error: cannot find symbol
pstmnt = setInt(1,id);
^
symbol: variable id
location: class mysql1
mysql1.java:86: error: cannot find symbol
pstmnt = setString(2,f);
^
symbol: variable f
location: class mysql1
mysql1.java:87: error: cannot find symbol
pstmnt = setInt(3,f);
^
symbol: variable f
location: class mysql1
mysql1.java:91: error: cannot find symbol
}while(ans=='y');
^
symbol: variable ans
location: class mysql1
mysql1.java:119: error: cannot find symbol
PreparedStatement ps = con.preparedStatement(updat);
^
symbol: method preparedStatement(String)
location: variable con of type Connection
mysql1.java:130: error: cannot find symbol
PreparedStatement ps1 = con.PreparedStatement(del);
^
symbol: method PreparedStatement(String)
location: variable con of type Connection
mysql1.java:169: error: cannot find symbol
inner1 = "select * from salary sal employe e on sal.id=e.id";
^
symbol: variable inner1
location: class mysql1
mysql1.java:170: error: cannot find symbol
rs5 = stmnt.executeQuery(inner1);
^
symbol: variable inner1
location: class mysql1
14 errors
我正在使用linux终端进行编译。我尝试将类和方法名称更改为大/小写。我还更改了类名并将整个程序复制到不同的文件然后编译。我还检查了“Eclipse IDE”中的代码，所以我也没有找到任何拼写错误。另外我想知道是否会自动调用连接器，如果没有，那么我应该进一步添加什么？
我是初学者，这是我的第一个JDBC代码，请帮忙。
答案 0 :(得分：0)
您的代码存在很多问题，其中一些可以避免1）仔细审查您的代码和2）使用IDE。
一些问题：
con.preparedStatement而不是con.prepareStatement，setXXX方法，例如pstmnt，ans不能在该块之外使用，inner1。