Android select from SQLite database where date (stored as int) = today?

Question

I have dates stored in a SQLite table in int format (ie milliseconds - derived from System.currentTimeMillis()). I now want to query all rows from the table where the date is equal to today's date, but the query below always returns zero, even though file_uploaded_date in the upload_history table is set to today's date in at least 20 rows. Can anyone tell me what's wrong with my query?

String today = new SimpleDateFormat("d-MMMM-yyyy").format(new Date());
String sql = "SELECT COUNT(*) as uploaded_today from upload_history "
    + "WHERE strftime('%-d-%b-%Y',file_uploaded_date) = strftime('%-d-%b-%Y','" + today + "')";
Cursor cursor = db.rawQuery(sql, null);
if(cursor != null && cursor.moveToFirst()){
   int uploadedToday = cursor.getInt(cursor.getColumnIndex("uploaded_today"));
}

Answer 1

I'd say you have your format-strings incorrect.

I don't see a %b argument in the documentation. For month, you would want to use %m . Also %-d doesn't seem right. Use the following format string instead: %Y%m%d .

Further, you are then passing a poorly-formatted string into the query, rather than the int, and relying an sqlite to correct that. Instead, compare to a SimpleDateFormat( "yyyyMMdd" ) without further conversion.

Your code would then look like this:

String today = new SimpleDateFormat("yyyyMMdd").format(new Date());
String sql = "SELECT COUNT(*) from upload_history "
    + "WHERE strftime('%Y%m%d',file_uploaded_date) = '" + today + "')";
Cursor cursor = db.rawQuery(sql, null);
if(cursor != null && cursor.moveToFirst()){
   int uploadedToday = cursor.getInt(0);
}

(Note that if you return only one column, you don't have to name it, and can just access the first column for the result.)

Further, please be aware that this query will cause a table-scan every time it's executed, as sqlite needs to convert all the epochs to strings. You'd be better off adding a date column to the table, and update it once:

UPDATE upload_history 
   SET just_the_date = strftime('%Y%m%d',file_uploaded_date)

This will then allow you to do much quicker searches, and even search by year or month, using the LIKE operator. If your table is very large, you might want to put an index on that column as well.

Answer 2

您可以在 db 中添加日期作为日期格式的字符串，例如 yyyy-mm-dd hh-mm-ss 并在使用 sql 查询从数据库中检索它时进行比较。