Generate Calendar Table from Min/Max Seed - powerquery

Question

I'm trying to create a calendar from YYYYMM (Integer) value in my SQL table. Here is the first step - getting the start value = "01 jan 2019" in a Date format. The code below returns an error with a description that it "cannot convert a value of type Record to type Text".
let
mySource=
Sql.Database("sqlServer"
,"DWH"
,[Query=
"SELECT
MIN(mdate) as mdate
FROM BD_plan_AC
UNION
SELECT
MAX(mdate) as mdate
FROM myTable"
]
)-- here I get the mdate range within I want to build my calendar.
-- from the first day of mdate to the end of the last mdate.
,startDateAsNum=Record.Field(Table.First (mySource),"mdate")*100+1
// Table.First (mySource),"mdate")=201901
// startDateAsNum=20190101
,startDateAsText=Text.From(startDateAsNum)
,startDateAsDate=Date.FromText(startDateAsText,[Format="yyyyMMdd"])
in
startDateAsDate
Many thanks in advance.
The idea is to get the mdate range and build a calendar from the first day of min to the last day of max, so, all dates from the range are in.
mySource = -- dates are not constant and comes from the query.
mdate
201901
202212
This, what I want to get finally - a calendar with a Date() data type. (Dates are as dd.mm.yyyy)
Date
01.01.2019
02.01.2019
....
31.12.2022

Answer 1

Given your input data, you can generate a calendar as follows.
let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwtDQwVIrVATGNjAyNlGJjAQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [mdate = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"mdate", type text}}),
start = #date( Number.From( Text.Range( #"Changed Type"[mdate]{0},0,4 )) ,Number.From( Text.Range( #"Changed Type"[mdate]{0},4,2 )),1 ),
end = #date( Number.From( Text.Range( #"Changed Type"[mdate]{1},0,4 )) ,Number.From( Text.Range( #"Changed Type"[mdate]{1},4,2 )),31 ),
cal = { Number.From( start ) .. Number.From( end ) },
#"Converted to Table" = Table.FromList(cal, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
#"Changed Type1" = Table.TransformColumnTypes(#"Converted to Table",{{"Column1", type date}})
in
#"Changed Type1"

Answer 2

Why do you need to do anything?
01 jan 2019 converts perfectly to a date with Date.From() in powerquery

Answer 3

try this to get the data from SQL in Format yyyymmdd then maybe you have to convert anything...
SELECT
format(cast(MIN(mdate) ,datetime),"YYYYMM") as mdate
FROM BD_plan_AC
UNION
SELECT
format(cast(MAX(mdate) ,datetime),"YYYYMM") as mdate
FROM myTable