Question

I want to get entries from a SQLite database by date.

SQLite valid timestring formats are listed here as:

YYYY-MM-DD
YYYY-MM-DD HH:MM
YYYY-MM-DD HH:MM:SS
YYYY-MM-DD HH:MM:SS.SSS
YYYY-MM-DDTHH:MM
YYYY-MM-DDTHH:MM:SS
YYYY-MM-DDTHH:MM:SS.SSS
HH:MM
HH:MM:SS
HH:MM:SS.SSS
now
DDDD.DDDD 

I have another format in the database that is D/M/YYYY

Is there a way to compare dates in this database (and select entries accordingly) without having to select, parse and compare all the DateTime objects from all rows in the table?

Answer 1

I made a really FAST query and I am proud of it :p. So here it is:

    public static string FromClausePartForDateComparisson(string tableName, string dateFieldName, string idFieldName, DateTime from, DateTime to)
    {
        string clause = string.Format(@" from 
           (SELECT {0} as filteredId,
                Substr('00'|| -- make day with two digits
                    CASE Substr({1}.{2}, 3, 1)
                        WHEN '/' THEN Substr({1}.{2}, 1, 2)
                        ELSE Substr({1}.{2}, 1, 1)
                    END, -2, 2) AS DAY,
                Substr('00'|| -- make month with two digits
                    CASE Length({1}.{2})
                        WHEN 8 THEN Substr({1}.{2}, 3, 1)
                        WHEN 9 THEN CASE Substr({1}.{2}, 3, 1)
                                        WHEN '/' THEN Substr({1}.{2}, 4, 1)
                                        ELSE Substr({1}.{2}, 3, 2)
                                    END
                        WHEN 10 THEN Substr({1}.{2}, 4, 2)
                    END, -2, 2) AS MONTH,
                Substr({1}.{2}, Length({1}.{2}) - 3, 4) AS YEAR
            FROM   {1}
            WHERE  Strftime('%Y%m%d', YEAR||'-'||MONTH||'-'|| DAY) BETWEEN
                    Strftime('%Y%m%d', '{3}') AND
                    Strftime('%Y%m%d', '{4}')) AS filteredtable
            INNER JOIN {1} ON filteredtable.filteredId = {1}.{0} ", idFieldName, tableName, dateFieldName, from.ToString("yyyy-MM-dd"), to.ToString("yyyy-MM-dd"));
        return clause;
    }

And it is being used as:

var selectCommand = new SQLiteCommand("SELECT * " + 
    FromClausePartForDateComparisson("TABLENAME", "DATE", "ID", from, to) +
    @"WHERE ID_TABLENAME=@Id";