PBI Flashcards
When can you import local files in Power BI
For data that does not change
Why might it be necessary to return and change connection settings in Power BI Desktop after creating a data source connection and loading data?
Due to changes in the organization’s security policy, such as updating passwords
What are the possible actions that can be taken when returning to change connection settings in Power BI Desktop after loading data?
data source, edit permissions or clear permissions.
When working in Power BI, what is the recommended best practice for optimizing data retrieval and usage from a relational database?
Writing a query in a view, similar to a table in a relational database
NoSQL (non-relational) databases
flexible database systems that do not use tables to store data
Preview pane for cosmo db (no sql db) shows
The preview pane only shows Record items because all records in the document are represented as a Record type in Power B
Importing the data in to Power BI means
that the data is stored in the Power BI file and gets published along with the Power BI reports
Why might you NOT want to use import mode in PBI
Security Reasons
Why is direct query useful?
because it ensures you’re always viewing the most recent version of the data.
The three different types of storage modes you can choose from:
Import
DirectQuery
Dual (Composite)
How to switch storage mode
Model view -> select a table -> Properties pane -> storage mode drop down
Import mode (3 attributes)
- Create a local PBI Copy of you semantic models
- Can use all PBI Services including Q&A and Quick Insights
- Data refreshed can be scheduled or on demand
DirectQuery Mode Attributes
- Useful when you dont want to save local copies of data (Data wont be cached)
- Direct connection to the data source
- Viewing most up to date data
- Suited for when you have large semantic models (Improved performance)
Dual (Composite mode)
- Can ID some data to be directly imported and other data the must be querried
- Limited M transformations
- Restricted DAX functions in calculated columns
- Same constraints as directquery
Azure Analysis Services
fully managed platform as a service (PaaS) that provides enterprise-grade semantic models in the cloud
differences between Azure Analysis Services and SQL Server are:
- Analysis Services models have calculations already created
- Can query the data directly using MDX or DAX
Fast Refresh Schedule Analysis Services
When data is refreshed in the service Power BI Reports will immediately be updated
The performance of Power Query depends on
The performance at the data source level
Power Query takes advantage of good performance at the data source through
Query Folding
Query folding
the process by which the transformations and edits that you make in Power Query Editor are simultaneously tracked as native queries, or simple Select SQL statements, while you’re actively making transformations
The benefits to query folding include:
- More efficiency in data refreshes and incremental refreshes.
- Automatic compatibility with DirectQuery and Dual storage modes.
If the View Native Query option isn’t available
then query folding isn’t possible for this step, and you’ll have to work backward in the Applied Steps area until you reach the step in which View Native Query is available (displays in bold type).
Native queries aren’t possible for the following transformations:
1.Adding an index column
2. Merging and appending columns of different tables with two different sources
3. Changing the data type of a column
Other ways to optimize query performance in Power BI include:
1.Process as much data as possible in the original data source.
2.Use native SQL queries.
3. Separate date and time, if bound together.
What is a query timeout in relational source systems?
Relational source systems often implement query timeouts to prevent a single user from monopolizing hardware resources. These timeouts limit the duration a query can run and can be configured for various timespans, from seconds to minutes or more. The purpose is to manage concurrent usage of data in the same database.
Power BI Query Error: Timeout expired
indicates that you’ve pulled too much data according to your organization’s policies.
Ways to resolve “Power BI Query Error: Timeout expired”
- Pull in fewer columns or rows
- Reduce complexity of SQL
- Bring data in small chunks and combine using Power Query
We couldn’t find any data formatted as a table error
When importing data from excel power bi may not be able to find a table
A calculated table formula must return
a table object
Calculated tables have a cost
- Increase the model storage size
- Prolong data refresh time
A calculate column must return
a scalar or single value
calculated columns in import models have a cost
- Increase the model storage size
- prolong the data refresh time
Row Context
The current row
Referencing a column in another table when the two tables are not related
Use the LOOKUPVALUE dax function
Relatedtable
Retrieves values on the many-side of a relationship and returns a table object
Iterator functions
provide you with flexibility to create sophisticated summarizations
Three ways to add columns
- Add columns to a view or table as a persisted column
- Add custom columns (using M) to Power Query queries
- add calculated columns (using DAX) to model tables
Preference to add custom columns
Is in Power Query whenever possible because they load to the model in a more compact and optimal way
Unpivot columns
- Creates Attribute and Value columns
Pivot columns
convert your flat data into a table that contains an aggregate value for each unique value in a column
Best practices when naming tables, columns and measures
- Remove “_”
- Remove prefixes and suffixes
Report objects include
- Visuals
- Elements