Spørgsmål Flashcards
Hvad er kardinalitet
- 1-1 Betyder at i noget kun kan være i begge tabel 1 gang. Der kan kun være 1 Land
- 1-x En til mange: Der kan være et land, men mange forskllige mennesker i det land
- x-x Mange til mange:
Natrual key
Kan entydigt forklare i en tabel - Entydigt hentyer til et produkt
Atomisk granularity
- Ned på en række, så langt ned man kan slice
- Hvis noget slettes er det den nuværene. Hvad er det en række repræsentrere
Bus Matrix
Matrix over dim og facts der er afhænige, eller når man kan slice gennem dem.
Story telling
At guide læseren, mod den retning der ønskes. At sørge for der de visuele elementer matcher ønsket.
MDM: Master data managment,
Sørger for der er en aurtoriativ (den vigtige) (1) sandhed - processer for at man kan validere. Opretholder en standartiseret sandhed gennem hele virksomehden - ved process håndtering
Hvad er Profilering
Dataprofilering er processen med at undersøge de tilgængelige data fra en eksisterende informationskilde og indsamle statistikker eller informative resume om disse data. Formålet med disse statistikker kan være at: Find ud af, om eksisterende data let kan bruges til andre formål
What are relational databases?
They are databases that have data stored in tables and any new information is automatically added into the table without the need to reorganize the table itself
A table can have multiple parents
Metadata present a more complete picture of the data in the database than the data itself.
True
In an SQL-based relational database, rows in different tables are related based on common values in common attributes.
True
How can businesses get the most out of their data?
Unlock data through accurate storytelling
What is Data Analysis? How does this work?
- Processing - Data analysis is the process of identifying, cleaning, transforming, and modelling data to discover meaningful and useful information.
- Selling Story - The data is then crafted into a story through reports for analysis to support the critical decision-making process.
Diagnostic analytics? What is the process?
- Diagnostic analytics answer questions about why events happened
- Diagnostic techniques supplement findings from descriptive statistics to uncover the cause of events (e.g. why these events became better or worse)
(1) Identify anomaly
(2) Collect data related to anomaly
(3) Use statistical techniques to discover relationships in these patterns
Predictive analytics?
- Predictive analytics techniques use historical data to identify trends and determine if they are likely to occur again in the future
- Usually one outcome
- Includes statistical and machine learning techniques
Prescriptive analytics?
- Prescriptive analytics help answer questions about which actions should be taken to achieve a goal or target.
- Analyses past data to estimate the likelihood of different outcomes (multiple outcomes)
- Uses machine learning techniques
Visualizations? What is the goal of a visualisation?
- A visualization (sometimes also referred to as a visual) is a visual representation of data, like a chart, a color-coded map, or other interesting things you can create to represent your data visually.
- Ultimate goal - to present data in a way that provides context and insights, both of which would probably be difficult to discern from a raw table of numbers or text.
Benefits of a good data model?
Data exploration is faster
Aggregations are simpler to build
Power BI Reports
Reports are more accurate
Writing reports takes less time
Reports are easier to maintain in the future
What are the differences between fact and dimension tables?
Fact table
- Observational/event data
- Contains measures and numbers
- Distinct values in multiple rows
Dimension table
- Contains details about the fact table
- Unique values appear in one row
What are hierarchies?
Natural segments in data that are capable of being decomposed
Systemic layers such as parent-child relationships or tree structures
What is flattening the parent-child hierarchy?
he process of viewing multiple child levels based on a top-level parent is known as flattening the hierarchy.
These uses multiple columns to indicate multiple levels
Flatten the hierarchy so you can see multiple individual levels
In this process, you are creating multiple columns in a table to show the hierarchical path of the parent to the child in the same record.
What is a role-playing dimension?
Role-playing dimensions have multiple valid relationships with fact tables, meaning that the same dimension can be used to filter multiple columns or tables of data.
Why are role-playing dimensions important to understand?
As a result, you can filter data differently depending on what information you need to retrieve
What is cardinality best practice?
Avoid one-to-one: Is not recommended because this relationship stores redundant information and suggests that the model is not designed correctly. It is better practice to combine the tables.
Avoid many-to-many: a lack of unique values introduces ambiguity and your users might not know which column of values is referring to what.
Explain the types of cardinality within Power BI?
Many-to-one (*:1) or one-to-many (1: *) cardinality:
Describes a relationship in which you have many instances of a value in one column that are related to only one unique corresponding instance in another column.
Describes the directionality between fact and dimension tables.
Is the most common type of directionality and is the Power BI default when you are automatically creating relationships.
One-to-one (1:1) cardinality:
Describes a relationship in which only one instance of a value is common between two tables.
Requires unique values in both tables.
Many-to-many (.) cardinality:
Describes a relationship where many values are in common between two tables.
Does not require unique values in either table in a relationship
