Q:

What is difference between s3 select and athena

I am trying to understand what is difference between aws athena service and newly released s3 select (still in preview). And how usecases different for both of those? It seems both helps in selecting partial data from s3.

A:

You can think about AWS S3 Select as a cost-efficient storage optimization that allows retrieving data that matches the predicate in S3 and glacier aka push down filtering. 
AWS Athena is fully managed analytical service that allows running arbitrary ANSI SQL compliant queries - group by, having, window and geo functions, SQL DDL and DML.

A:

Athena is (from the little I've used it) more intended as a business reporting or analysis tool backed by S3.
S3 select appears to use the same sort of technology, but I would guess it's aimed more at direct use by applications to filter or shard their data sets.

A:

To give an overview as per my understanding :

Amazon Athena is an interactive query service that makes it easy to
  analyze data in Amazon S3 using standard SQL. Athena is serverless, so
  there is no infrastructure to manage, and you pay only for the queries
  that you run.

The Major Advantage of this as of now is :
Athena is out-of-the-box integrated with AWS Glue Data Catalog, you can also use Glue’s fully-managed ETL capabilities to transform data or convert it into columnar formats to optimize cost and improve performance.
Now as far the S3 Select Goes :

At present, there is no charge for using S3 Select while it is in
preview, and there is no definition of pricing. However, you will
need to apply at the reference
While in preview S3 Select supports CSV, JSON, and Parquet files with or without GZIP compression. During the preview objects that are encrypted at rest are not supported.
Because S3 Select is still in preview, AWS doesn't have internal
cases to verify how the service is being used. However, I could find
a reference from a blog that might interest you.

In my opinion, you can view this Twitch Video that can help you lot.

