Develop tables in Looker

Question 1

What is a derived table in Looker?

Answer 1

A query whose results are used as if the query were an actual table in the database.

Question 2

What can you compute with a derived table?

Answer 2

Customer-level aggregate metrics such as how many orders each customer has placed or when each customer placed their first order.

Question 3

What is the purpose of the derived_table parameter?

Answer 3

• To define a derived table under a view parameter.

Question 4

What are the two ways to define a derived table in Looker?

Answer 4

• Native derived table with LookML-based query
• SQL-based derived table with SQL query

Question 5

What is a native derived table?

Answer 5

A derived table based on queries defined using LookML terms.

Question 6

What is a SQL-based derived table?

Answer 6

A derived table defined using a SQL query.

Question 7

What is the main advantage of native derived tables over SQL-based derived tables?

Answer 7

Native derived tables are easier to read and understand.

Question 8

What SQL command is used to create a persistent derived table (PDT)?

Answer 8

CREATE TABLE Data Definition Language (DDL) statement.

Question 9

What is the purpose of the create_process parameter?

Answer 9

To create a PDT in multiple steps if the dialect does not support a single-step CREATE TABLE statement.

Question 10

What is the difference between temporary and persistent derived tables?

Answer 10

• Temporary derived tables are not written to the database.
• Persistent derived tables are written to a schema on your database.

Question 11

What happens when a user runs an Explore query involving a temporary derived table?

Answer 11

Looker constructs a SQL query using the derived table(s) plus requested fields, joins, and filter values.

Question 12

True or False: SQL-based derived tables can be incrementally built.

Answer 12

False.

Question 13

Fill in the blank: To create a native derived table, you use the _______ parameter.

Answer 13

explore_source

Question 14

What is the sql parameter used for in SQL-based derived tables?

Answer 14

To define a query in SQL terms.

Question 15

What is an important consideration for naming columns in SQL-based derived tables?

Answer 15

Each column should have a clean alias using AS.

Question 16

What type of derived tables are created by default if no persistence strategy is defined?

Answer 16

Temporary derived tables.

Question 17

What is the purpose of the sql_create parameter?

Answer 17

To create a PDT using custom DDL commands.

Question 18

What does Looker use when cached results are valid for a temporary derived table query?

Answer 18

The cached results.

Question 19

What should be ensured about temporary derived tables?

Answer 19

They should be performant and not put excessive strain on the database.

Question 20

In the context of Looker, what is a view?

Answer 20

A representation of a derived table that can be used like any other table in the database.

Question 21

List the fields included in the customer_order_summary derived table.

Answer 21

• customer_id
• first_order
• total_amount

Question 22

What parameter is used to create a derived table in Looker?

Answer 22

derived_table

Question 23

What are the two ways to define a derived table in Looker?

Answer 23

• LookML-based query
• SQL-based query

Question 24

What is a native derived table?

Answer 24

A derived table based on queries defined using LookML terms

Question 25

What parameter do you use to define a query for a native derived table?

Answer 25

explore_source

Question 26

In a native derived table, how are the columns created?

Answer 26

By referring to LookML dimensions or measures

Question 27

What is the main advantage of native derived tables over SQL-based derived tables?

Answer 27

They are easier to read and understand

Question 28

What is a SQL-based derived table?

Answer 28

A derived table defined using a SQL query

Question 29

What parameter is commonly used to define a SQL query in a SQL-based derived table?

Answer 29

sql

Question 30

Can you refer to LookML dimensions and measures in a SQL-based derived table?

Answer 30

No

Question 31

What is the purpose of the SQL Runner in Looker?

Answer 31

To create SQL queries and turn them into derived table definitions

Question 32

What is a persistent derived table (PDT)?

Answer 32

A derived table that is stored in the database for reuse

Question 33

What is the create_process parameter used for?

Answer 33

To create a PDT in multiple steps when a single CREATE TABLE statement is not supported

Question 34

What should you ensure when defining columns in a SQL-based derived table?

Answer 34

Give each column a clean alias using AS

Question 35

What is the sql_create parameter used for?

Answer 35

To create a PDT with custom DDL commands

Question 36

Fill in the blank: The two versions of the LookML illustrate how to create equivalent derived tables using either _______ or _______.

Answer 36

[LookML] [SQL]

Question 37

True or False: Both native and SQL-based derived tables can use the same derived_table parameter.

Answer 37

True

Question 38

What fields are included in the customer_order_summary derived table?

Answer 38

* customer_id * first_order * total_amount

Question 39

What does the dimension_group for first_order in the native derived table include?

Answer 39

* type: time * timeframes: [date, week, month]

Question 40

What SQL function is used to determine the first order date in the SQL-based derived table?

Answer 40

MIN(DATE(time))

Question 41

What must you include in the SQL query to reference column names in dimensions?

Answer 41

Clean aliases using AS