สอบถามการค้นหา ชื่อ วรรค นามสกุล ใน SQL ต้องเขียนคำสั่ง where ยังไง

Private Sub SearchButton_Click(sender As Object, e As EventArgs)
    Dim connectionString As String = "Data Source=(local);Initial Catalog=mydatabase;Integrated Security=True"

    Using connection As New SqlConnection(connectionString)
        connection.Open()

        Dim sql As String = "DECLARE @input NVARCHAR(100) = @full_name" & vbCrLf &
                            "DECLARE @first_name NVARCHAR(50), @last_name NVARCHAR(50)" & vbCrLf &
                            vbCrLf &
                            "SET @first_name = LTRIM(LEFT(@input, CHARINDEX(' ', @input + ' ') - 1))" & vbCrLf &
                            "SET @last_name = LTRIM(RIGHT(@input, LEN(@input) - CHARINDEX(' ', @input)))" & vbCrLf &
                            vbCrLf &
                            "SELECT * FROM users WHERE first_name LIKE '%' + @first_name + '%' AND last_name LIKE '%' + @last_name + '%'"

        Using command As New SqlCommand(sql, connection)
            command.Parameters.AddWithValue("@full_name", fullNameTextBox.Text)

            Dim adapter As New SqlDataAdapter(command)
            Dim table As New DataTable()

            adapter.Fill(table)

            resultsDataGridView.DataSource = table
        End Using
    End Using
End Sub