There are two types of external tables – Hadoop and Native external tables that can be used to read and export data depending upon the type and format of the external data source. Which of the following statements are true about these external tables? (Select all that are applicable)

Answer options:

A.Hadoop external tables are only available in dedicated SQL pools, but not in serverless SQL pools.
B.Hadoop external tables are only available in serverless SQL pools, but not in dedicated SQL pools.
C.Native external tables are available in serverless SQL pools but are not available in dedicated Synapse SQL pools.
D.Native external tables are available in serverless SQL pools, but in Synapse SQL pools, they are only in gated preview.
E.The files having the name started with a period (.) or an underline (_) are skipped by both Hadoop as well as native external tables while reading the data.
F.Only the files having the name started with underline (__), not period(_) are skipped by both external tables.
G.Hadoop considers all files and skips no file irrespective of its name.

Correct Answers: A, D and E 
The below table highlights the major differences between Hadoop external table and the Native external table: 

Option A is correct. Hadoop external tables are available only in dedicated SQL pools, but not in serverless SQL pools.
Option B is incorrect. Hadoop external tables are only available in dedicated SQL pools, but not in serverless SQL pools.
Option C is incorrect. Native external tables are available in serverless SQL pools, and also available in dedicated Synapse SQL pools but only in gated preview.
Option D is correct. Native external tables are available in serverless SQL pools, but in Synapse SQL pools, they are only in gated preview.
Option E is correct. The files having the name started with a period (.) or an underline (_) are skipped by both Hadoop as well as native external tables while reading the data.
Option F is incorrect. Both types of files having the name started with a period (.) or an underline (_) are skipped by both types of external tables.
Option G is incorrect. Hadoop external tables skip the files having the name started with a period (.) or an underline (_).
Reference: 
To know more about using external tables with Synapse SQL, please visit the below-given link: 

https://docs.microsoft.com/en-us/azure/synapse-analytics/sql/develop-tables-external-tables?tabs=hadoop