Question

创建新表时遇到一些问题。当我使用CREATE TABLE命令时，我的新表格应该如此形成，但当我退出活动时，应用程序崩溃，我在logcat中获得了一个TABLE ALREADY EXISTS。如果我使用CREATE TABLE IF NOT EXISTS，则不会形成新表，只是将新的数据行添加到上一个表中，并且不会崩溃。这有什么问题？我想添加没有它的表给我已经存在，我希望它添加没有它添加行到不同的表。

SqliteHelper类：

public class MySQLiteHelper extends SQLiteOpenHelper {


public static final String TABLE_NAME = MainActivity.NameName;

public static final String COLUMN_ID = "_id";
public static final String COLUMN_COMMENT = "comment";
public static final String COLUMN_LAT = "lat";
public static final String COLUMN_LONG = "long";
public static final String COLUMN_RADI = "radi";
private static final String DATABASE_NAME = "spraylogs.db";
private static final int DATABASE_VERSION = 1;



public static final String NEWTABLE = "CREATE TABLE  "
         + TABLE_COMMENTS + "(" + COLUMN_ID
          + " integer primary key autoincrement, " + COLUMN_COMMENT
          + " text not null," + COLUMN_LAT+ ","  + COLUMN_LONG + "," + COLUMN_RADI +  ");";

public static final String SaveIt = "CREATE TABLE IF NOT EXISTS "
         + TABLE_COMMENTS + "(" + COLUMN_ID
          + " integer primary key autoincrement, " + COLUMN_COMMENT
          + " text not null," + COLUMN_LAT+ ","  + COLUMN_LONG + "," + COLUMN_RADI +  ");";



 MySQLiteHelper(Context context) {
  super(context, context.getExternalFilesDir(null).getAbsolutePath() + "/" + DATABASE_NAME, null, DATABASE_VERSION);
}


@Override
public void onCreate(SQLiteDatabase database) {
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(MySQLiteHelper.class.getName(),
    "Upgrading database from version " + oldVersion + " to "
        + newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + NEWTABLE);

onCreate(db);
 } 

}

Answer 1

这就是应该如何运作的。如果表已存在，CREATE TABLE将抛出异常。如果表不存在，CREATE TABLE IF NOT EXISTS将创建表，否则忽略该命令。如果您希望删除旧表，请在DELETE TABLE IF EXISTS之前使用CREATE TABLE。如果要更改架构，请使用ALTER TABLE，而不是CREATE TABLE。

Answer 2

我这样用：

   internal static int checkTable()
    {
        DataTable dTable = new DataTable();
        try
        {
            dbConn = new SQLiteConnection("Data Source=" + dbFileName + ";Version=3;");
            dbConn.Open();
            sqlCmd.Connection = dbConn;

            String makeTable = "CREATE TABLE IF NOT EXISTS responde( id INTEGER PRIMARY KEY AUTOINCREMENT, sid TEXT, ans TEXT, answe TEXT, questid TEXT, timestamp TEXT)";

            sqlCmd.CommandText = makeTable;
            sqlCmd.ExecuteNonQuery();
            return 1;
        }
        catch (SQLiteException) { Console.WriteLine("Error DB 100"); return 0; }
        catch (IndexOutOfRangeException) { Console.WriteLine("Error DB 101"); return 0; }
        catch (TypeInitializationException) { Console.WriteLine("Error DB 102"); return 0; }
    }

android sqlite CREATE TABLE IF NOT NOT EXISTS

2 个答案: