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Filtering Numeric Fields

     

Introduction

As done for strings, if a field holds both numeric and null values, to find out whether a field holds a null value, apply the IS NULL expression to its condition.

Here is an example:

SELECT [Shelf #], Title, [Year]
FROM Videos
WHERE [Year] IS NULL;
GO

Unlike strings, number-based fields use all Boolean operators supported both by ISO SQL anbd Transact-SQL. They are:

Operation Used to find out whether
= A field holds a certain numeric value
<> or != A field doesn't hold a certain numeric value or a field has a value different from a certain numeric value
< A field's value is lower than a certain numeric value
<= or !> A field's value is lower than or is equal to a certain numeric value or a field's value is not greater than a certain numeric value
> A field's value is greater than a certain numeric value
>= or !< A field's value is greater than or is equal to a certain numeric value or a field's value is greater than or is equal to a certain numeric value

Here is an example:

void btnSelectClick(object sender, EventArgs e)
{
    using (SqlConnection connection =
        new SqlConnection("Data Source=(local);" +
                          "Database='VideoCollection1';" +
                          "Integrated Security=yes;"))
    {
        SqlCommand command =
            new SqlCommand("SELECT ALL * FROM Videos " +
                           "WHERE [Length] > 125;",
                           connection);
        connection.Open();
        command.ExecuteNonQuery();

        SqlDataAdapter sdaVideos = new SqlDataAdapter(command);
        BindingSource bsVideos = new BindingSource();

        DataSet dsVideos = new DataSet("VideosSet");
        sdaVideos.Fill(dsVideos);

        bsVideos.DataSource = dsVideos.Tables[0];
        dgvVideos.DataSource = bsVideos;
    }
}

This would produce:

Boolean Operations on Numeric Fields

The Negativity or Opposite of a Numeric Comparison

There are various ways you can find the negation of a number-based comparison. As seen previously, to negate a comparison, you can precede the expression with the NOT operator. Otherwise, by definition, each Boolean operator has an opposite. They are:

Operation Opposite
Primary Also Primary Also
= <> !=
<> != =
< !< >=
<= > !>
> !> <=
>= < !<

Based on this, to find the negativity of a comparision, you can use the opposite operator.

 

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