Avatto>>DATA SCIENTIST>>SHORT QUESTIONS>>Tableau Interview Questions
In Star schema, the Fact is at the center and surrounded by dimension tables. A snowflake schema is similar to star schema. In Snowflake schema, dimension table/s may be connected to other related dimensions. For example, the Product dimension may connect to the Category dimension. What is a Snowflake scheme?
When creating a dashboard, it is important to get the requirements from the users. When gathering requirements,

  • -Take data requirements. Data sources, key filters, data refresh frequency.

  • -Ask users about the KPI (Key Performance Indicators).

  • -Inquire about the questions users are trying to answer.

  • -Document business rules required for the dashboards.

  • -Understand security requirements.

  • -Gather details about any existing reports or desired visualization.

  • -Provide layout of the screen in terms of a dashboard- charts, and tables in excel or hand-drawn. Get the user's feedback on the layout.

  • -Get requirements about the screen resolution.
A primary key uniquely identifies a record in a table. The primary key in one table is referenced by a foreign key in another table. Two relational tables are linked based on the primary key and foreign key.
The joins in SQL are:

a) Inner Join. Returns matching rows from both the tables.
b) Left/Outer join. Returns all rows from the left table and the matched rows from the right table.
c) Right/Outer join. Returns all rows from the Right table and the matched rows from the left table.
d) Full/Outer join. Returns all rows from table1 and from the table. It combines the result of both LEFT and RIGHT joins.
e) Cartesian join. Join every row of one table to every row of another table.
Union and Union All are used to combine the results of queries. Union eliminates duplicate records and Union All includes all the records.