Tableau Desktop Specialist (TDS-C01) Study Notes

Data Connections and Extracts

Connecting and Preparing Data is 25% of the exam (~11 questions).

Feature	Live Connection	Extract (.hyper)
Data freshness	Always current	Snapshot at time of extract
Performance	Depends on DB speed	Fast — optimized columnar storage
Works offline	No	Yes
Best for	Real-time data needs	Large datasets, offline, faster queries
Security	DB credentials required	Data copied to .hyper file

Method	When to Use	Key Behavior
Join	Two tables from the same data source	Physical merge — can create duplicate rows with multiple fact tables
Relationship	Tableau default (recommended)	Context-aware, no duplicates, lazy loading, preserves granularity
Union	Stack rows from similar table structures	Appends rows — tables must have same or compatible columns
Blend	Different data sources in same view	Acts like a left join; primary source drives; secondary aggregates

Extension	Description
.twb	Tableau Workbook — XML file, references data sources externally
.twbx	Tableau Packaged Workbook — includes data + workbook in one file
.tds	Tableau Data Source — connection metadata only, no data
.tdsx	Tableau Packaged Data Source — metadata + local file data
.hyper	Tableau Extract — optimized columnar data file
.tde	Old extract format (replaced by .hyper since Tableau 10.5)

Aliases — rename dimension member values (e.g., 'NY' → 'New York')
Geographic Roles — assign lat/lon, city, country, state, etc. to enable map views
Default Aggregation — change a measure's default from SUM to AVG, MIN, MAX, COUNT, etc.
Data Type — change String/Number/Date/Boolean in the data pane
Rename fields — double-click a field name in the Data pane

Data Connections and Extracts

Connecting and Preparing Data is 25% of the exam (~11 questions).

Feature	Live Connection	Extract (.hyper)
Data freshness	Always current	Snapshot at time of extract
Performance	Depends on DB speed	Fast — optimized columnar storage
Works offline	No	Yes
Best for	Real-time data needs	Large datasets, offline, faster queries
Security	DB credentials required	Data copied to .hyper file

Method	When to Use	Key Behavior
Join	Two tables from the same data source	Physical merge — can create duplicate rows with multiple fact tables
Relationship	Tableau default (recommended)	Context-aware, no duplicates, lazy loading, preserves granularity
Union	Stack rows from similar table structures	Appends rows — tables must have same or compatible columns
Blend	Different data sources in same view	Acts like a left join; primary source drives; secondary aggregates

Extension	Description
.twb	Tableau Workbook — XML file, references data sources externally
.twbx	Tableau Packaged Workbook — includes data + workbook in one file
.tds	Tableau Data Source — connection metadata only, no data
.tdsx	Tableau Packaged Data Source — metadata + local file data
.hyper	Tableau Extract — optimized columnar data file
.tde	Old extract format (replaced by .hyper since Tableau 10.5)

Aliases — rename dimension member values (e.g., 'NY' → 'New York')
Geographic Roles — assign lat/lon, city, country, state, etc. to enable map views
Default Aggregation — change a measure's default from SUM to AVG, MIN, MAX, COUNT, etc.
Data Type — change String/Number/Date/Boolean in the data pane
Rename fields — double-click a field name in the Data pane