The final group of M queries, parameter table queries, are developed for usability and manageability purposes. From a usability standpoint, the Date Intelligence Metrics and Adventure Works Sales queries serve to consolidate similar DAX measures in the Fields list. Additionally, the CurrentDate query is used to provide reports with a text message advising of the latest data refresh date. From a manageability standpoint, the Measure Support query can be used to centralize intermediate or branching DAX expressions that can be referenced by many DAX measures.

As shown in the following example of the Adventure Works Sales query, a trivial expression can be used for three of the four queries since the purpose of the query is simply to provide a table name to the data model:

The Date Intelligence Metrics, Adventure Works Sales, and Measure Support queries can all retrieve a blank value and the Include in report refresh property can be disabled. The following two chapters will demonstrate how these blank tables can be utilized as data model metadata, and DAX measures are added to the dataset in Chapter 3, Designing Import and DirectQuery Data Models, and Chapter 4, Developing DAX Measures and Security Roles, respectively. 

The CurrentDate query is the only parameter table query that needs to be executed with each report refresh. The following M script for the CurrentDate query produces a table with one column and one record, representing the current date as of the time of execution:

let
    RefreshDateTime = DateTime.LocalNow(),
    TimeZoneOffset = -5,
    RefreshDateTimeAdjusted = RefreshDateTime + #duration(0,TimeZoneOffset,0,0),
    RefreshDateAdjusted = DateTime.Date(RefreshDateTimeAdjusted),
    TableCreate = Table.FromRecords({[CurrentDate = RefreshDateAdjusted]}),
    DateType = Table.TransformColumnTypes(TableCreate,{"CurrentDate", type date})
in
    DateType

All reported times in Microsoft Azure are expressed in Coordinated Universal Time (UTC). Therefore, timezone adjustment logic can be built into the M query to ensure the last refreshed date message reflects the local timezone. In the preceding example, five hours are reduced from the DateTime.LocalNow() function reflecting the variance between US Eastern Standard Time and UTC. The adjusted datetime value is then converted into a date value and a table is built based on this modified date value. 

As shown in the following image, the Adventure Works Sales and Date Intelligence Metrics queries are represented in the FIELDS list and the CurrentDate query is used by a DAX measure to advise of the last refreshed date:

The DAX expression supporting the last refreshed message is as follows:

Last Refresh Msg = 
  VAR CurrentDateValue = MAX('CurrentDate'[CurrentDate])
  RETURN "Last Refreshed: " & CurrentDateValue 

An additional example of using DAX to return a string value for title or label purposes is included in the Drillthrough Report Pages section of Chapter 6, Applying Custom Visuals, Animation, and Analytics.