Question

我有两个布尔列的以下示例数据：

ID      Male      Female
1        1          0
2        0          1
3        0          1
4        1          0
5        0          1

我想将两列合并为一个只包含'M'和'F'的列。另外，我最好在定义列时在SELECT语句中执行此操作。

结果应该是：

ID     Gender
1        M
2        F
3        F
4        M
5        F

我知道我可以通过单独的更新语句实现这一点，例如：

UPDATE table_1
SET Gender='M'
FROM table_2 t2
WHERE t2.Male=1

和

UPDATE table_1
SET Gender='F'
FROM table_2 t2
WHERE t2.Female=1

但我真的希望在宣布性别列时能够达到相同的效果吗？

有人知道这是否可行？

提前致谢！

Answer 1

您可以使用CASE表达式。

<强>查询

UPDATE t1
SET t1.Gender = (
    CASE WHEN t2.Male = 1 AND t2.Female = 0 THEN 'M'
    WHEN t2.Male = 0 AND t2.Female = 1 THEN 'F'
    ELSE NULL END
)
FROM Table_1 t1
JOIN Table_2 t2
ON t1.ID = t2.ID;

Answer 2

 <System.Web.Services.WebMethod()>
    Public Shared Sub UploadFile()
        Try
            Dim file As HttpPostedFile = HttpContext.Current.Request.Files("file")
            Dim fname As String = Path.GetFileName(file.FileName)
            Dim ftype As String = file.ContentType
            Dim sDatasource As String = String.Empty
            Dim inputArray(flen) As Byte
            Dim myStream As System.IO.Stream
            If (Current.Request.Files.Count > 1) Then
                file = HttpContext.Current.Request.Files("file")
                fname = Path.GetFileName(file.FileName)
                ftype = file.ContentType
                flen = file.ContentLength

                myStream = file.InputStream
                'read the file into the byte array
                myStream.Read(inputArray, 0, flen)
            End If
            If Not HttpContext.Current.Session.Contents("datasource") Is Nothing Then sDatasource = HttpContext.Current.Session.Contents("datasource").ToString()
            Using con As New SqlConnection(sDatasource)
                Using cmd As New SqlCommand
                    cmd.CommandText = "test_insertDoc"
                    cmd.CommandType = CommandType.StoredProcedure
                    cmd.Parameters.AddWithValue("referenceno", 0)
                    cmd.Parameters.AddWithValue("doctype", ftype)
                    cmd.Parameters.AddWithValue("line", 0)
                    cmd.Parameters.Add("uploadedfile", SqlDbType.VarBinary, -1).Value = inputArray
                    cmd.Parameters.AddWithValue("customer", 0)
                    cmd.Parameters.AddWithValue("warehouse", 0)
                    cmd.Connection = con
                    con.Open()
                    cmd.ExecuteNonQuery()
                    con.Close()
                    cmd.Dispose()
                End Using
            End Using
        Catch ex As Exception
        End Try
    End Sub

当然我试图保持开放态度并猜测你允许UPDATE table_1 SET Gender= CASE WHEN Male = 1 THEN 'M' WHEN Female = 1 THEN 'F' ELSE 'Other' // optional END; 否则，您可以使用 IIF

进行简化

Male = 0 and Female = 0

Answer 3

以下是使用SELECT语句的方法：

SELECT ID,
CASE WHEN Male = 1 THEN 'M'
ELSE 'F' END AS gender
FROM My_Table

Answer 4

select if(Male = 1, 'M', 'F') as gender怎么样？

结合两列SQL的布尔结果

4 个答案: