How to create table from list while specifying column name as well as its type

Hi Anonymous 

Using Table.SelectColumns is still the simplest method. 

In addition, to construct a single-column table with #table, it should be

let
    Source = #table(
        type table 
            [
                From = text
            ],
        {
            {"aa"},
            {"bb"}
        }
    )
in
    Source

When you use RenameColumnsMappings[From] to extract the column, it returns a result like {"aa", "bb"}. While the expected result in #table() should be {{"aa"},{"bb"}}. So it didn't construct the table correctly. 

To convert {"aa", "bb"} into {{"aa"},{"bb"}}, you can use List.Transform - PowerQuery M

List.Transform(#"Changed Type"[From], each {_})

Full code

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSkxU0lGqqFCK1YlWSkoCsisrlWJjAQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [From = _t, To = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"From", type text}, {"To", type text}}),
    Custom1 = List.Transform(#"Changed Type"[From], each {_}),
    newTable = #table(
        type table 
            [
                From = text
            ],
        Custom1
    )
in
    newTable

Hope it helps

Best Regards,
Community Support Team _ Jing
If this post helps, please Accept it as Solution to help other members find it.

Hi Anonymous 

Your question is valid, and you can indeed specify the column name and type within the Table.FromList function. Let me give you an example. The below code creates a single column table with the name "Product" and the data type Text. 

= Table.FromList(
    {"Apple", "Prume" },
    null,
    type table[Product=Text.Type]
)

You can achieve something similar with the methods:

- #table

- Table.FromRecords

- Table.FromColumns

- Table.FromRows

Hope this helps!

Rick

https://gorilla.bi

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