Tableau Flashcards
Alias
Definition: An alternate name for members in a dimension. It makes a label appear differently in the view.
Discrete dimensions only. Aliases cannot be used for continuous dimensions, dates, or measures.
Histogram
Looks like a bar chart
Each bar represents data points that fall within a given range (a “bin”)
Geographic Role
Tableau assigns latitude and longitude values to every geographic role.
How to assign a geographic role to a field: In the data pane, click the data type icon next to the field, select Geographic Role, and then select the precise role needed.
How to change a data field’s data type
Can be done on either the Data Source page or the Data pane.
Click the icon to the left of the field name and choose the new type.
Relationships vs. Joins
Relationships:
- The primary means of combining data in Tableau
- More dynamic and flexible than joins
- Are displayed as flexible noodles between logical tables
- Require you to select matching fields between two logical tables
- Do not require you to select join types
- Make all row and column data from related tables potentially available in the data source
- Maintain each table’s level of detail in the data source and during analysis
- Create independent domains at multiple levels of detail. Tables aren’t merged together in the data source.
- During analysis, create the appropriate joins automatically, based on the fields in use.
- Do not duplicate aggregate values (when Performance Options are set to Many-to-Many)
- Keep unmatched measure values (when Performance Options are set to Some Records Match)
Joins:
- No longer the primary means of combining data in Tableau
- More static than relationships
- Are displayed with Venn diagram icons between physical tables
- Require you to select join types and join clauses
- Joined physical tables are merged into a single logical table with a fixed combination of data
- May drop unmatched measure values
- May duplicate aggregate values when fields are at different levels of detail
- Support scenarios that require a single table of data, such as extract filters and aggregation
Types of LOD Expressions
There are three LOD expressions:
- FIXED - computes a value using the specified dimensions without reference to the dimensions in the view
- INCLUDE - computes a value using the specified dimensions in addition to whatever dimensions are in the view
- EXCLUDE - declares dimensions to omit from the view level of detail
Joins
The merging of multiple data sources based on each source’s leftmost column of data.
There are four join types:
- Inner: matches in both tables
- Left: all values from the left table and any matches from the right table. When a value in the left table doesn’t have a match in the right table, you see a null value.
- Right: all values from the right table and any matches from the left table. When a value in the right table doesn’t have a match in the left table, you see a null value.
- Full Outer: all values from both tables. When a value from either table doesn’t have a math with the other table, you see a null value.
Unions
Combining data sources by appending rows of one table into another table.
Fields (aka column headers) must match for the union to work correctly.
Discrete Date Parts vs. Continuous Date Values
Discrete Date Parts
- Blue
- Produce headers in a view
- Behave like dimensions
Continuous Date Values
- Green
- Produce axes in a view
- Behave like measures
Parameter
A workbook variable that replaces a constant value in a calculation, filter, or reference line.
Parameters can depend on the input of the user.
Aggregation type: Dimension
Returns a list of all unique values in a measure or dimension.
Example: if the measure contains values [1, 2, 2, 3] the Dimension aggregation will return [1, 2, 3]
Aggregation type: Attribute
Returns the value only if all rows have the same value, otherwise it returns an asterisk.
Dimension vs. Measure
Dimension = qualitative values. Examples: names, dates, geographical data
Measure = numeric, quantitative values. Measures are aggregated when added to a view. The type of default aggregation depends on the context of the view.
Dimensions and measures can be either discrete or continuous.
Data Sources: Live Connection vs. Extract
Live connection: direct connection to underlying data, providing real-time data. Fresher data but slower performance. Stored in storage (hard drive) as opposed to memory (RAM).
Extract: a snapshot of data. Optimized for aggregation. Faster performance but less fresh data. .tde or .hyper file types. Extracts are stored in memory (RAM) as opposed to storage (hard drive).
Discrete fields vs. Continuous fields
Discrete = Blue. Finite. Column headers.
Continuous = Green. Infinite. Axes.