SQLite检查列是否存在

Question

I want to check columns (not value) at agregasi table, if columns exist do something, but if columns does not exist show/print message 'Column does not exist' . I could run code below while columns exist:

String keywords1={'pesawat','terbang'}; 
String sql1 = "SELECT " + keywords + " FROM agregasi"; //columns exist at agregasi table
Cursor c1 = myDbHelper.rawQuery(sql1, null);
if (c1.moveToFirst()) {
   // i can do something (no problem)
}

But i have problem when columns name i change on purpose (to check). What should i do to print error message (in android/java way)?

**String keywords2={'psawat','terang'};** 
String sql2 = "SELECT " + keywords + " FROM agregasi"; //columns does not exist at table 
Cursor c2 = myDbHelper.rawQuery(sql2, null);
// what should i do get error message and show/print using toast

Answer 1

You're looking for getColumnIndex(String columnName) .

int index = c2.getColumnIndex("someColumnName");
if (index == -1) {
    // Column doesn't exist
} else {
    ...
}

Answer 2

Here's a general method you can use to check whether a particular column exists in a particular table:

public boolean isColumnExists(SQLiteDatabase sqliteDatabase,
                              String tableName,
                              String columnToFind) {
    Cursor cursor = null;

    try {
        cursor = sqLiteDatabase.rawQuery(
                "PRAGMA table_info(" + tableName + ")",
                null
        );

        int nameColumnIndex = cursor.getColumnIndexOrThrow("name");

        while (cursor.moveToNext()) {
            String name = cursor.getString(nameColumnIndex);

            if (name.equals(columnToFind)) {
                return true;
            }
        }

        return false;
    } finally {
        if (cursor != null) {
            cursor.close();
        }
    }
}

Answer 3

Try this it works fine :)

Cursor res = db.rawQuery("PRAGMA table_info("+tableName+")",null);
int value = res.getColumnIndex(fieldName);