Power BI - handling non-existing arguments and returning data in table for valid arguments

Question

I am stuck at the error handling routine. I have this function..

(LicenceNumber) =>
let
Source = 
Web.Page(Web.Contents("http://mbsweblist.fsco.gov.on.ca/ShowLicence.aspx?M" 
& Number.ToText(LicenceNumber) & "~")),
WebData = Source{1}[Data],
#"Extracted Text Before Delimiter" = Table.TransformColumns(WebData, 
{{"Column1", each Text.BeforeDelimiter(_, ":"), type text}}),
#"Removed Top Rows" = Table.Skip(#"Extracted Text Before Delimiter",1),
#"Transposed Table" = Table.Transpose(#"Removed Top Rows"),
#"Promoted Headers" = Table.PromoteHeaders(#"Transposed Table", 
[PromoteAllScalars=true])
in
#"Promoted Headers"

Which returns data to table

let
Source = {13000246..13000250},
#"Convert to Table" = Table.FromList(Source,Splitter.SplitByNothing(),{"Licence Number"}),
#"Changed Type" = Table.TransformColumnTypes(#"Convert to Table",{{"Licence Number", Int64.Type}}),
#"Get WebData" = Table.AddColumn(#"Changed Type", "WebData", each try WebData([Licence Number]) otherwise #table({},{})),
#"Combine WebData" = Table.Combine(#"Get WebData"[WebData]),
#"Changed Types" = Table.TransformColumnTypes(#"Combine WebData",{{"Agent/Broker Name", type text}, {"Licence #", type text}, {"Brokerage Name", type text}, {"Licence Class", type text}, {"Status", type text}, {"Issue Date", type date}, {"Expiry Date", type date}, {"Inactive Date", type date}})
in
#"Changed Types"

I am trying to error handle a situation where I pass an invalid value in source, lets say source = {13009995..13009999}, this is throwing error - "col X of table was not found". I tried to use the following error handling logic but it is not working ..

Empty = #table({{"Agent/Broker Name", type text}, {"Licence #", type text}, 
{"Brokerage Name", type text}, {"Licence Class", type text}, {"Status", type 
text}, {"Issue Date", type date}, {"Expiry Date", type date}, {"Inactive 
Date", type date}},{}),
Combine = Table.Combine({#"Get WebData"[WebData], Empty}),

I am primarily a business analyst and unable to fix this error. Requesting help. User Olly had helped me with my primary query

M has a handy `try ... otherwise ...` that might be of use to you. More details [here](https://blog.gbrueckl.at/2013/12/error-handling-in-power-query/). — Alexis Olson, Dec 05 '18 at 16:18
that has been given in this step, #"Get WebData" = Table.AddColumn(#"Changed Type", "WebData", each try WebData([Licence Number]) otherwise #table({},{})), still it errors out if it gets a non-existing license — suji, Dec 05 '18 at 16:29

Alexis Olson · Accepted Answer · 2018-12-05T17:13:20.513

I would suggest creating an empty table as a separate query called EmptyTable that matches the columns when you do get data back. Here's the M code for that:

let
    Empty =
    #table(
        {
        "Agent/Broker Name",
        "Licence #",
        "Brokerage Name",
        "Licence Class",
        "Status",
        "Issue Date",
        "Expiry Date",
        "Inactive Date"
        },
        {}
    )

in
    Empty

Now in your #"Get WebData" step, simply swap out #table({},{}) for EmptyTable.

#"Get WebData" =
Table.AddColumn(
    #"Changed Type",
    "WebData",
    each
        try WebData([Licence Number])
        otherwise EmptyTable
),

Note: Your query looks to work fine when there is at least one valid license number.

Power BI - handling non-existing arguments and returning data in table for valid arguments

1 Answers1