SQLite 数据库与 C# 无法比较日期时间数据类型

Question

I am using C# (.NET) and SQLite database with it. I have a table in an SQLite database with a column called "InvoiceDate". I have chosen the datatype (in the db table) for the same as TEXT as I need it to be a datetime variable.

I am using the System.Data.SQLite reference .

The following is my command text where I am facing the problem:

command.CommandText = "SELECT * FROM InvoiceMaster WHERE InvoiceDate BETWEEN '" 
                     + date1.ToString() + "' AND '" 
                     + date2.ToString() + "' ORDER BY InvoiceNumber";

I need to find all results where the column InvoiceDate falls between the given dates date1 and date2. But the problem is that I am getting the results even though I choose other dates for example I get the same results for the same month and dates even though I choose a different year. There is something wrong with the command text and I also need to know what type of datatype should I choose in the db table. Please do let me know how I should be writing the select command.

Answer 1

From 1.2 Date and Time Datatype

TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS")

Since ToString() does not generate this kind of format, you can use custom formatting like;

date1.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)
date2.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)

But more important, you should always use parameterized queries . This kind of string concatenations are open for SQL Injection attacks.

I'm not %100 about format but you might wanna use The "o" standard format specifier which represents;

.. a custom date and time format string using a pattern that preserves time zone information and emits a result string that complies with ISO 8601.

command.CommandText = @"SELECT * FROM InvoiceMaster 
                        WHERE InvoiceDate BETWEEN @date1 AND @date2 
                        ORDER BY InvoiceNumber";

command.Parameters.AddWithValue("@date1", date1.ToString("o"));
command.Parameters.AddWithValue("@date2", date1.ToString("o));

Answer 2

You can create a method to convert your datetime

 private string DateTimeSQLite(DateTime datetime)
  {
    string dateTimeFormat = "{0}-{1}-{2} {3}:{4}:{5}.{6}";
    return string.Format(dateTimeFormat, datetime.Year,   
                         datetime.Month,datetime.Day, 
                         datetime.Hour, datetime.Minute,  
                          datetime.Second,datetime.Millisecond);
  }

or better make it a extension method.

 private static string DateTimeSQLite(this DateTime datetime)
 {}

Also use parametrized queries to avoid sql injection

string commandText = "SELECT * FROM InvoiceMaster 
                  WHERE InvoiceDate BETWEEN @date1 and @date2
                  ORDER BY InvoiceNumber"
yourcommand.Parameters.Add("@date1",date1.DateTimeSQLite());
yourcommand.Parameters.Add("@date2",date1.DateTimeSQLite());

Answer 3

Since you have chosen to store the dates as TEXT field in the database, they must be formatted using ISO8601. Example:

2016-02-03T20:34:22Z

So once you have ensured that they are stored this way all that's left is parametrize your query:

DateTime date1 = ... get from somewhere
DateTime date2 = ... get from somewhere

using (var conn = new SQLiteConnection("Data Source=mydb.db;Version=3;"))
using (var cmd = conn.CreateCommand())
{
    conn.Open();
    cmd.CommandText = "SELECT * FROM InvoiceMaster WHERE InvoiceDate BETWEEN @startDate AND @endDate";
    cmd.Parameters.AddWithValue("@startDate", date1.ToString("o"));
    cmd.Parameters.AddWithValue("@endDate", date2.ToString("o"));
    using (var reader = cmd.ExecuteReader())
    {
        while (reader.Read())
        {
            // do something with the results here
        }
    }
}

Notice how I am using the .ToString("o") format specifier to ensure that the dates will be passed correctly to the database.