Power Query as staging table - free Power BI account

[szczawek]

Hi all,

I am not very good in M and Power Query so i decided to ask someone better than me 😉

The goal i would like to achive is to have staging table of prices per day from currency exchange web site.

I need to use free Power BI account to do it.

I was trying to create 2 tables:

1. Pull - this query is downloading data from web page at refresh

2. StagingCurrency - this is staging table

For staging I tried to do as follow:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i44FAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Currency = _t, Sell = _t, Buy = _t, Date = _t, Tag = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Currency", type text}, {"Sell", type number}, {"Buy", type number}, {"Date", type datetime}, {"Tag", type text}}),
    #"Appended Query" = Table.Combine({#"Changed Type", Pull}),
    Custom1 = #"Appended Query"
in
    Custom1

Table StagingCurrency is created as enter data -  i listed columns to match Pull table.

Expected logic is to load data for table from Pull and then add new values after next refresh without wiping out current data.

Currently result is that after refresh i have only latest data from Pull table, all previous data are cleared.

Best

K

[lbendlin · Accepted solution]

Power BI has no memory.  You cannot use it as a staging tool.  There's a thing called dataflows and you could theoretically use these with incremental refresh.  But that would be a strategy based on hope. 

You need to find another tool to do that, for example SQL Server Developer /Express - those are free. Or a bunch of CSV files.