I have the following code in a bigger project:
final class DBlifetimeStatisticsHandler{ //implements DBvalueHandler<Cyclist, Double>{
private final String TAG = getClass().getName();
private static final boolean debug = true;
private final DBminMaxAvgHandler dbMinMaxAvgHandler = new DBminMaxAvgHandler();
// table name
private static final String TABLE_LIFETIME_STATISTICS = "lifetime_statistics";
// column names
private static final String KEY_LIFETIME_STATISTICS_ID = "lifetime_statistics_id";
private static final String KEY_MIN_MAX_AVG = "min_max_avg";
// table create statement
private static final String CREATE_TABLE = "CREATE TABLE "
+ TABLE_LIFETIME_STATISTICS + "("
+ KEY_LIFETIME_STATISTICS_ID + " LONG PRIMARY KEY NOT NULL,"
+ KEY_MIN_MAX_AVG + " LONG"
+ ")";
public void onCreateTable(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
}
public void onUpgrade(SQLiteDatabase db) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_LIFETIME_STATISTICS);
onCreateTable(db);
}
public long addValue(SQLiteDatabase db, Statistics Statistics ) {
ContentValues values = new ContentValues();
long ID = getLatestID(db)+1;
values.put(KEY_STATISTICS_ID, ID);
... //not important to the question
}
private long getLatestID(SQLiteDatabase db){
String selectQuery = "SELECT MAX(" + KEY_STATISTICS_ID +") FROM " + TABLE_STATISTICS;
Cursor c = db.rawQuery(selectQuery, null);
c.moveToFirst();
int id = 0;
Log.e("count", String.valueOf(c.getCount()));
if (c.moveToFirst()){
...
}
return id;
}
}
After I updated the table it is created again. So when I try to add a new value I had problems cause it always jumped into the if clause because c.moveToFirst()
always returned true.
So I tried to tried to check if c.getCount()
would return true but sadly it does always return 1. So the question is: Why would it return 1 on an empty table? (I do use Questoid SQLite Browser and the table is really empty)
You use aggregate function MAX
, so read documentation:
There are two types of simple SELECT statement - aggregate and non-aggregate queries. A simple SELECT statement is an aggregate query if it contains either a GROUP BY clause or one or more aggregate functions in the result-set.
An aggregate query without a GROUP BY clause always returns exactly one row of data, even if there are zero rows of input data.