从 Power Query 中的单元格值中提取数据类型？

Posted 2023-04-14

【中文标题】从 Power Query 中的单元格值中提取数据类型？

【英文标题】：Extract Datatype from Cell Values in PowerQuery?

【发布时间】：2021-12-13 22:22:58

【问题描述】：

如何将每个单元格的数据类型保存到新列中？我希望“自定义”列显示“值”列中每个项目的数据类型。我试过使用Value.Type([values])，但输出只显示这个“类型”值。如果我点击“类型”，它会创建一个新的导航查询，我可以看到数据类型保存在其中，但我似乎无法提取它们。

【问题讨论】：

有趣的问题。 This 是一个可能的解决方案，但我不喜欢它。

谢谢！该解决方案有效。在拆分列后尝试使用此方法时，我现在面临一个新问题：***.com/questions/70342312/…

【参考方案1】：

原始类型与归属类型

@AlexisOlson：

This 是一个可能的解决方案，但我不喜欢它。

你是对的，那个答案是不正确的。它使用Table.Schema，which tests for ascribed types That's usually the right type, but if data isn't transformed correctly, it can be wrong

您需要使用Value.Type() 来获取真实/实际的primitive type

查询

let
    Sample = 
        123, 0.45, true,
        "text",
        Currency.From(12.34),
        Int64.From(91),
        DateTime.LocalNow(), DateTimeZone.FixedLocalNow(), #date(2021,1,3),
        #duration(0,0,1,3), #binary(2,3,4),
        #table(type table[Foo=text], "bar"),
        [ a = "b" ],
        each "x",
        0..3
    ,
    records = List.Transform(
        Sample,
        (item) => [
            Original = item, 
            Name = TypeToText( Value.Type( item )) 
        ]
    ),
    Final = Table.FromRecords( records, type table[Original = any, Name = text])
in
    Final

Type.ToText.pq

这是_serialize_typename() 的简化版本，其中包含DataConnectors/UnitTesting.query.pq 的真正序列化

let
    Type.ToText =  (x, optional funtype as logical) =>
        let
            isFunctionType = (x as type) => try if Type.FunctionReturn(x) is type then true else false otherwise false,
            isTableType = (x as type) =>  try if Type.TableSchema(x) is table then true else false otherwise false,
            isRecordType = (x as type) => try if Type.ClosedRecord(x) is type then true else false otherwise false,
            isListType = (x as type) => try if Type.ListItem(x) is type then true else false otherwise false
        in
            if funtype = null and isTableType(x) then "Table"
            else if funtype = null and isListType(x) then "list"
            else if funtype = null and isFunctionType(x) then "Function"
            else if funtype = null and isRecordType(x) then "Record"
            else if x = type any then "any"
            else let base = Type.NonNullable(x) in
                (if Type.IsNullable(x) then "nullable " else "") &
                (if base = type anynonnull then "anynonnull" else
                if base = type binary then "binary" else
                if base = type date   then "date"   else
                if base = type datetime then "datetime" else
                if base = type datetimezone then "datetimezone" else
                if base = type duration then "duration" else
                if base = type logical then "logical" else
                if base = type none then "none" else
                if base = type null then "null" else
                if base = type number then "number" else
                if base = type text then "text" else
                if base = type time then "time" else
                if base = type type then "type" else

                /* Abstract types: */
                if base = type function then "function" else
                if base = type table then "table" else
                if base = type record then "record" else
                if base = type list then "list"
                else "any /*Actually unknown type*/")
in
    Type.ToText