Question

I am facing huge issues with running date-related queries on the local SQLite database, kindly appreciate your help on this!

I am trying to retrieve all events that have its eventdate within a given year and month. To do this, I calculated the first date and last date of that month, then queried where the event date is within this range.

My test data uses:
String[] testEventDates = {“2011-12-17”, “2012-02-25”, “2012-01-10”, “2012-01-01”,
“2011-12-24″,”2012-02-25”}

But when I run my query below, I get ALL of these entries retrieved, which is wrong. My query is, (SELECT…WHERE) “eventDate >= ” + firstDay.

When I add the other limit, ” AND “eventDate < ” + lastDay,
it also works weirdly, the cursor is null instead.

Please help me if you have any clues about this!

// fetch events by month, between first and last days calculated
public Cursor fetchEventsByMonth(int month, int year) {
    String firstDay, lastDay, correctedMonth;

    if (month == 12) {
        lastDay = Integer.toString(year+1) + "-01-01";
    } else{
        if (month+1 < 10) {
            correctedMonth = "0" + Integer.toString(month+1);
            } else correctedMonth = Integer.toString(month+1);
        lastDay = Integer.toString(year) + "-" + correctedMonth
                + "-01";
    }
    if (month < 10) {
        correctedMonth = "0" + Integer.toString(month);
        } else correctedMonth = Integer.toString(month);
    firstDay = Integer.toString(year) + "-" + correctedMonth + "-01";
    firstDay = "2012-02-25";

    Cursor mCursor =
    mDb.query(DATABASE_TABLE_EVENTS, new String[] { KEY_EID, KEY_ENAME,
            KEY_EINTERESTS, KEY_EBENS, KEY_EDATE, KEY_ETIME, KEY_EVHO, KEY_EABBR,
            KEY_ELOCATION, KEY_ETYPE, KEY_ENATURE, KEY_ESTATUS, 
            KEY_ESIGNEDUP, KEY_ECAPACITY}, "eventDate >= " + firstDay
            // + " AND "eventDate < " + lastDay
                    , null, null, null,
            "eventDate");
    if (mCursor != null) mCursor.moveToFirst();

    return mCursor;
}   

Answer 1

Have you tried to reproduce the query directly? (I mean querying the database with some tools like SQLite Manager).

NB: when you are using STRINGS you have ALWAYS to use single quote!
I also modified it to use selection and selection args, so you are much security safer and it do the job of inserting the single quote automatically. Try it
So your query have to be:

Cursor mCursor =
    mDb.query(DATABASE_TABLE_EVENTS, new String[] { KEY_EID, KEY_ENAME,
            KEY_EINTERESTS, KEY_EBENS, KEY_EDATE, KEY_ETIME, KEY_EVHO, KEY_EABBR,
            KEY_ELOCATION, KEY_ETYPE, KEY_ENATURE, KEY_ESTATUS, 
            KEY_ESIGNEDUP, KEY_ECAPACITY}, "eventDate >= ? AND eventDate < ?"
                    , new String[] { firstDay, lastDay}, null, null,
            "eventDate");
    if (mCursor != null) mCursor.moveToFirst();

Also a really big advice is to never store dates and times with strings. First of all because they are static in this way, instead you have to think that people live in different countries with different times and timezones so you have to think in a worldwide way 🙂

The best way to store dates and times is (in my opinion) with a long (time stamp).
So when you retrieve a date/time you can pass directly it to a Date constructor or a Calendar constructor. Also it’s much, much much easier to compare dates in that way and it’s really much faster than String compare 🙂