To view all indexes for a table or view, you can use sp_helpindex.
By default, the query optimizer already updates statistics as necessary to improve the query plan; in some cases you can improve query performance by using UPDATE STATISTICS or the stored procedure sp_updatestats to update statistics more frequently than the default updates.
An example of a "read-only operation" is a data analysis on a data dump from some app or research study.
For example, if I was a data scientist working for a daily diary, I might query what percentage of users eat ice cream on the same day that they run, to understand if exercise makes people want to reward themselves: An example of "read/write operations" is a software engineer creating the backend for a webapp.
Joomla's database querying has changed since the new Joomla Framework was introduced "query chaining" is now the recommended method for building database queries (although string queries are still supported).
Query chaining refers to a method of connecting a number of methods, one after the other, with each method returning an object that can support the next method, improving readability and simplifying code.