Power query

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#sqlsat462November 28°, 2015
Power Query
Marco Pozzan
@marcopozzan.it
www.marcopozzan.it

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Sponsors

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Organizers
getlatestversion.it

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Marco Pozzan | @marcopozzan.it
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www.beantech.it
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• www.innovazionefvg.net
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– info@marcopozzan.it
– www.marcopozzan.it
– http://www.scoop.it/u/marco-pozzan
– http://paper.li/marcopozzan/1422524394

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– Power Pivot (analysis)
– Power View (reporting)
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– Query sharing with other subscribers

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• You get prompted the first time you try to connect to a data source
• Edit or remove credentials using the Data Source Settings button
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• Prevents Power Query from sending private data to public data sources
• You get prompted the first time you join/merge the data source with another
• Levels: Public,Organizational, Private

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– Merge two Power Query queries by matching values in columns
– Like SQL inner join and left join
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– Append output of Power Query query into another query, it combines
columns with the same name
– Like SQL Union

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DEMO 0
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• http://www.comuni-italiani.it/001/033/index.html

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– There are no real looping constructs but objects like lambda functions
– is a functional language Nothing like Excel formula language or VBA 
– Understanding M for writing more complex transformations and calculations
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– Can be invoked dynamically with Evaluate
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o Familiar, easy to remember
o Easy to read and write; limited syntax, use of non standard symbols
o A superset of the Excel formula language
o Powerful capabilities for the advanced user

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– 3 + 3 is an expression
– 3 + 3 return the value 6
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– Primitives types like: Boolean , text , number, null, logical, number, text, binary, any,
none, Time, date, datetime, datetimezone, duration
– Complex types like: record, list, table, function, user defined, (data and code)!

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[
Man = [Athletic = 10 , NonAthletic = 50 ],
Woman = [Athletic = 20 , NonAthletic = 40 ],
Total = Man[Athletic] + Woman[Athletic]
]
= [Athletic = 10 , NonAthletic = 50]

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– to a position N of a list
– a row in a table
[
Data = {
[Athletic = 10 , NonAthletic = 50 ],
[Athletic = 20 , NonAthletic = 40 ]
},
Total = data{0}[Athletic] + data{1}[Athletic]
]
= { 1..7 }

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=#table(
{"A", "B"},
{
{1, 2},
{3, 4}
}
)

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– Result of previous step typically used in the next step
– Step can be defined and reused later on
– Step isn’t evaluated if it isn’t used
let
Source = Sql.Database(".", "AdventureWorksDW2012"),
Sales = Table.FirstN(Source{[Schema="dbo",Item="Sales"]}[Data],10),
Rank = List.Sort(Sales[SalesAmount] ,Order.Ascending),
in
Rank
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– These become the steps in a query
– Each query created by the UI consist of a let single expression
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– This is the output of the query
– It can reference any of the expressions

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DEMO 1

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– A function is a value which, when invoked with arguments, produces a new value.
– Function are written by listing the function’s parameters in parentheses, followed
by the goes-to symbol =>, followed by the expression defining the function.
(x) => (x*x) //Multiply the value x to x
(x,y) => (x*y) //Multiply the value x to y
[
Mol = (x,y) = > x*y
]

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DEMO 2
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DEMO 3
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DEMO 4
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– = Table.RemoveRowsWithErrors(#"Changed Type", {"Età"})
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– Table.ExpandRecordColumn(#"Inserted Eta_Try", "Eta_Try", {"HasError", "Value",
"Error"}, {"Eta_Try.HasError", "Eta_Try.Value", "Eta_Try.Error"}),

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o Attempts evaluation
o Encodes results and errors as record values
o Optional otherwise clause
=Table.AddColumn(Source, “Eta_Bis", each try Number.From([Età]) otherwise 0)
try error "Bad"
// [ HasError = true,
// Error = [
// Reason = "Expression.Error",
// Message = "Bad",
// Detail = null
// ]
// ]
try error "Bad" otherwise 42 // 42

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DEMO 5

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– When?
o Column filters, row filters, joins, group by, pivot, unpivot
o Numeric calculations, aggregations
– Functionality depends on the data source
o Relational sources (SQL Server, Oracle, etc) support the
most functionality
o Also fold to OData, Active Directory, Exchange, and others
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o Use Table.Buffer() or List.Buffer()
o By combining data from multiple data sources with different privacy level
o Preventing query folding with custom SQL (Sql.Database("localhost","adventureworkdw",[Query="select * from dimdate"])

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– if you provide a native SQL query this is performed directly in the source data
– that the queries are optimized (i.e. nolock ) .
– Useful when user does not want rewrite in M language an existing query
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– Query isn't parsed before sending it to the source
– Can’t guarantee how often it is executed

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DEMO 6
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– Different visibility levels: private, group, public (within the company)
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– In this case the query is copied and executed locally, there are not processing on the
server

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DEMO 7
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– Generate steps using the UI, then tweak the code
– Formatting is easier in the UI
– Some things only work through the UI (“auto steps”)
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– Use #shared to see all exported functions (and keywords)
– Typing in the function name will display its help, and prompt for parameter
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– Use try/catch to isolate errors
– Select and remove rows with errors
– Table.Buffer will stop folding from occurring

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– Certify query
– Consume views
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http://www.microsoft.com/en-us/download/details.aspx?id=39933
http://go.microsoft.com/fwlink/?LinkID=235475

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Q&A
Questions?

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THANKS!
http://speakerscore.com/PowerQuery
https://app.bingpulse.com/eventspulse/sqlsaturday462
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