如何在android sqlit中添加主键
如何在android sqlit中添加主键
提问于 2015-08-09 23:27:43
我已经创建了一个存储学生记录的数据库。但是有一个重复的问题。我给不同的学生输入了相同的学号。但我希望在下面的代码中添加主键。如何将滚动号作为主键。并且还显示消息“该号码已经存在”
db=openOrCreateDatabase("StudentDB", Context.MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS student(rollno VARCHAR,name
name VARCHAR,marks VARCHAR);");
public void onClick(View view)
{
if(view==btnAdd)
{
if(editRollno.getText().toString().trim().length()==0||
editName.getText().toString().trim().length()==0||
editMarks.getText().toString().trim().length()==0)
{
showMessage("Error", "Please enter all values");
return;
}
db.execSQL("INSERT INTO student
VALUES('"+editRollno.getText()+"','"+editName.getText()+
"','"+editMarks.getText()+"');");
showMessage("Success", "Record added");
clearText();
}
if(view==btnDelete)
{
if(editRollno.getText().toString().trim().length()==0)
{
showMessage("Error", "Please enter Rollno");
return;
}
Cursor c=db.rawQuery("SELECT * FROM student WHERE
rollno='"+editRollno.getText()+"'", null);
if(c.moveToFirst())
{
db.execSQL("DELETE FROM student WHERE
rollno='"+editRollno.getText()+"'");
showMessage("Success", "Record Deleted");
}
else
{
showMessage("Error", "Invalid Rollno");
}
clearText();
}
if(view==btnModify)
{
if(editRollno.getText().toString().trim().length()==0)
{
showMessage("Error", "Please enter Rollno");
return;
}
Cursor c=db.rawQuery("SELECT * FROM student WHERE
rollno='"+editRollno.getText()+"'", null);
if(c.moveToFirst())
{
db.execSQL("UPDATE student SET
name='"+editName.getText()+"',marks='"+editMarks.getText()+
"' WHERE rollno='"+editRollno.getText()+"'");
showMessage("Success", "Record Modified");
}
else
{
showMessage("Error", "Invalid Rollno");
}
clearText();
}
if(view==btnView)
{
if(editRollno.getText().toString().trim().length()==0)
{
showMessage("Error", "Please enter Rollno");
return;
}
Cursor c=db.rawQuery("SELECT * FROM student WHERE
rollno='"+editRollno.getText()+"'", null);
if(c.moveToFirst())
{
editName.setText(c.getString(1));
editMarks.setText(c.getString(2));
}
else
{
showMessage("Error", "Invalid Rollno");
clearText();
}
}
if(view==btnViewAll)
{
Cursor c=db.rawQuery("SELECT * FROM student", null);
if(c.getCount()==0)
{
showMessage("Error", "No records found");
return;
}
StringBuffer buffer=new StringBuffer();
while(c.moveToNext())
{
buffer.append("Rollno: "+c.getString(0)+"\n");
buffer.append("Name: "+c.getString(1)+"\n");
buffer.append("Marks: "+c.getString(2)+"\n\n");
}
showMessage("Student Details", buffer.toString());
}
if(view==btnShowInfo)
{
showMessage("Student Management Application", "Developed By princ");
}
}
public void showMessage(String title,String message)
{
Builder builder=new Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(message);
builder.show();
}
public void clearText()
{
editRollno.setText("");
editName.setText("");
editMarks.setText("");
editRollno.requestFocus();
}所以在这段代码中，rollno我想把它作为主键，如果我使用相同的rollno，那么它应该会显示消息“该rollno已经存在”。
回答 2
Stack Overflow用户
发布于 2015-08-09 23:33:29
只需将uniq字段添加到表中，如下所示
uid integer primary key autoincrement这会解决你的问题
Stack Overflow用户
发布于 2015-08-09 23:34:17
public class FoodDbHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "PKFkM.DB";
private static final int DATABASE_VERSION = 1;
private static final String CREATE_QUERY =
"CREATE TABLE "+ Food.NewDishInfo.TABLE_NAME+"("
+ Food.NewDishInfo.DISH_NAME+" TEXT unique,"
+ Food.NewDishInfo.DISH_QUANTITY+" TEXT NOT NULL,"
+ Food.NewDishInfo.DISH_CALORIE+" INTEGER,"
+ Food.NewDishInfo.DISH_FAT+" TEXT NOT NULL,"
+ Food.NewDishInfo.DISH_PROTEIN+" TEXT NOT NULL,"
+ Food.NewDishInfo.DISH_SUGAR+" TEXT NOT NULL,"
+ Food.NewDishInfo.DISH_CARBOHYDRATES+" TEXT NOT NULL);";
public FoodDbHelper(Context context)
{
super(context,DATABASE_NAME,null,DATABASE_VERSION);
Log.e("DATABASE OPERATION","Database created / opened...");
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_QUERY);
Log.e("DATABASE OPERATION","Table created...");
}我想这样对你完全有帮助
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原文链接：
https://stackoverflow.com/questions/31905821
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