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SELECT X.*, Y.*
FROM (
	SELECT Id, Foo, Bar
	FROM (
		VALUES ('Id0', 'Foo0', 'Bar0'), ('Id1', 'Foo1', 'Bar1')
		) AS AliasTableNameX(Id, Foo, Bar)
	) AS X
INNER JOIN (
	SELECT *
	FROM (
		VALUES ('Id1', 'Foo1', 'Bar1', 1), ('Id2', 'Foo2', 'Bar2', 2), ('Id3', 'Foo3', 'Bar3', 3)
		) AS AliasTableNameY(Id, Foo, Bar, Price)
	) AS Y
	ON x.id = y.id

Imports System.Text
Imports System.Data.Common
Imports System.Math

Public Class MathExt
    Sub New()
    End Sub

    'ตัดเศษทิ้งในทุกฯกรณี
    ''' <summary>
    ''' ตัดเศษทิ้งทั้งหมด
    ''' Truncate(1.9999) --> Result = 1
    ''' </summary>
    ''' <param name="dblValue"></param>
    ''' <returns></returns>
    ''' <remarks>
    ''' 
    ''' </remarks>
    Public Shared Function Truncate(ByVal dblValue As Double) As Double
        Return Truncate(dblValue)
    End Function

    ''' <summary>
    ''' ตัดเศษทิ้งทั้งหมด
    ''' </summary>
    ''' <param name="decValue"></param>
    ''' <returns></returns>
    ''' <remarks>
    ''' Example
    ''' Truncate(1.9999) --> Result =1
    ''' </remarks>
    Public Shared Function Truncate(ByVal decValue As Decimal) As Decimal
        Return Truncate(decValue)
    End Function

    'Truncate a Decimal Number to Some Fixed Decimal Places
    'FixDecimal(120.123456, 5) --> 120.12345
    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="number"></param>
    ''' <param name="digits"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Function FixDecimal(ByVal number As Decimal, ByVal digits As Integer) As Decimal
        Dim x As Integer = 10 ^ digits
        Return Microsoft.VisualBasic.Conversion.Fix(number * x) / x

        'Fix(number) is equivalent to Sign(number) * Int(Abs(number)).
        ' This code requires Option Strict Off
        'Dim MyNumber As Integer
        'MyNumber = Int(99.8)   ' Returns 99.
        'MyNumber = Fix(99.8)   ' Returns 99.

        'MyNumber = Int(-99.8)  ' Returns -100.
        'MyNumber = Fix(-99.8)  ' Returns -99.

        'MyNumber = Int(-99.2)  ' Returns -100.
        'MyNumber = Fix(-99.2)  ' Returns -99.

        'MyNumber = CInt(99.8)    ' Returns 100.
        'MyNumber = CInt(-99.8)   ' Returns -100.
        'MyNumber = CInt(-99.2)   ' Returns -99.
    End Function

    'Truncate a Double Number to Some Fixed Double Places
    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="number"></param>
    ''' <param name="digits"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Function FixDouble(ByVal number As Double, ByVal digits As Integer) As Double
        Dim x As Integer = 10 ^ digits
        Return Microsoft.VisualBasic.Conversion.Fix(number * x) / x
    End Function

    'ปัดสิบ/ปัด? แบบปัดขึ้นหรือปัดลง เป็นจำนวนเต็ม(Integer) เช่น
    ' 21 = 20 หรือ 21 = 30 เป็นต้น
    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="intValue"></param>
    ''' <param name="UpDown"></param>
    ''' <param name="Nearest"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function IntegerNearEst(ByVal intValue As Integer, Optional ByVal UpDown As String = "U", Optional ByVal Nearest As Integer = 10) As Double
        'Return If(UpDown.ToUpper() = "U", System.Math.Ceiling(intValue / 10), System.Math.Floor(intValue / 10)) * 10
        Return If(UpDown.ToUpper() = "U", System.Math.Ceiling(intValue / Nearest), System.Math.Floor(intValue / Nearest)) * Nearest
    End Function

    ''' <summary>
    '''  ยามเหงาเราถอนใจ บินไปไม่กลับมา
    ''' </summary>
    ''' <typeparam name="T"></typeparam>
    ''' <param name="list"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function GetPowerSet(Of T)(ByVal list As IList(Of T)) As IEnumerable(Of IEnumerable(Of T))
        Dim x = From m In Enumerable.Range(0, 1 << list.Count)
                Select From i In Enumerable.Range(0, list.Count)
                       Where (m And (1 << i)) <> 0
                       Select list(i)
        Return x

    End Function

    ''' <summary>
    '''  ภาพอดีตยังงาม ล้ำล้น
    ''' </summary>
    ''' <param name="x"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function Factorial(x As Long) As Long
        If x <= 1 Then
            Return 1
        Else
            Return x * Factorial(x - 1)
        End If
    End Function

    ' การเรียงสับเปลี่ยน
    ' For Permutation nPr= n!/(n-r)!
    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="n"></param>
    ''' <param name="r"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function Permutation(n As Long, r As Long) As Long
        If r = 0 Then
            Return 0
        End If
        If n = 0 Then
            Return 0
        End If
        If (r >= 0) AndAlso (r <= n) Then
            Return Factorial(n) \ Factorial(n - r)
        Else
            Return 0
        End If
    End Function

    'การจัดกลุ่ม
    'For Combination nCr=n!/(n-r)!r!
    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="a"></param>
    ''' <param name="b"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function Combination(a As Long, b As Long) As Long
        If a <= 1 Then
            Return 1
        End If
        Return Factorial(a) \ (Factorial(b) * Factorial(a - b))
    End Function

End Class

' The example displays the following output to the console: 
'         Value          Ceiling          Floor 
'        
'          7.03                8              7 
'          7.64                8              7 
'          0.12                1              0 
'         -0.12                0             -1 
'          -7.1               -7             -8 
'          -7.6               -7             -8

'ปัดเศษขึ้น ให้เป็นจำนวนเต็ม
'System.Math.Ceiling

'ปัดเศษลง ให้เป็นจำนวนเต็ม
'System.Math.Floor

'ปัดเศษ ขึ้นก็ได้/ลงก็ได้ 

'Round() Rounds a value to the nearest integer or to the specified number of fractional digits.