For a duration, the sql_start and sql_end fields can be which of the following?

The correct answer is the option that includes all statements as valid choices for the sql_start and sql_end fields used in Looker for defining durations.

Both sql_start and sql_end can utilize SQL expressions that either represent a timestamp or pull time directly from the database, providing flexibility depending on the specific needs of the analysis. Utilizing SQL expressions allows for precise control over how dates and times are handled, which is essential for accurate duration calculations and analyses.

Additionally, referencing an existing dimension group is also valid because dimension groups in Looker often encapsulate date or time fields that can simplify the management of time-based data. This versatility means that users can define durations in a variety of helpful ways, depending on the logical structure of their database and reporting requirements.

By combining these approaches, Looker ensures that developers can create accurate and meaningful duration calculations that meet diverse analytics needs, further demonstrating the importance of having multiple options for defining time-related fields.