SQL 如何在选择查询中创建新列
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How to create a new column in a select query
提问by Martin08
In MS Access, I want to insert a new column into the returned result of a select query. The new column has the same value for every row. For example, my select returns columns A, B and I want C to be the new column created by the select query:
在 MS Access 中，我想在选择查询的返回结果中插入一个新列。新列的每一行都具有相同的值。例如，我的选择返回列 A、B，我希望 C 成为由选择查询创建的新列：
A B C
----------
a1 b1 c
a2 b2 c
a3 b3 c
回答by RedFilter
select A, B, 'c' as C
from MyTable
回答by Chenthil
SELECT field1, field2, 'example' AS newfield FROM TABLE1 This will add a column called "newfield" to the output, and its value will always be "example".
SELECT field1, field2, 'example' AS newfield FROM TABLE1 这将向输出添加一个名为“newfield”的列，其值将始终为“example”。
回答by onedaywhen
It depends what you wanted to do with that column e.g. here's an example of appending a new column to a recordset which can be updated on the client side:
这取决于您想对该列做什么，例如，这是将新列附加到可以在客户端更新的记录集的示例：
Sub MSDataShape_AddNewCol()
Dim rs As ADODB.Recordset
Set rs = CreateObject("ADODB.Recordset")
With rs
.ActiveConnection = _
"Provider=MSDataShape;" & _
"Data Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=C:\Tempo\New_Jet_DB.mdb"
.Source = _
"SHAPE {" & _
" SELECT ExistingField" & _
" FROM ExistingTable" & _
" ORDER BY ExistingField" & _
"} APPEND NEW adNumeric(5, 4) AS NewField"
.LockType = adLockBatchOptimistic
.Open
Dim i As Long
For i = 0 To .RecordCount - 1
.Fields("NewField").Value = Round(.Fields("ExistingField").Value, 4)
.MoveNext
Next
rs.Save "C:\rs.xml", adPersistXML
End With
End Sub
