I'm new to elasticsearch.I have learnt how to give different queries and get search results with the understanding that each document is stored in json format.Is it possible to insert records that were obtained from an sql query on a relational database?If it is possible,how is it done? by converting each record into json format?
You need to build an index in elasticsearch similar to the way you've got your tables in the RMDBS, this can be done in a lot of ways and it really depends on what data you would need to access via elasticsearch. You shouldnt just dump your complete RMDBS data into ES.
If you search around you may find bulk data importers/synchronisers/rivers(deprecated) for your RMDBS to ES, some of these can run in the background and keep the indexes in ES upto date with your RMDBS.
You can create your own code as well which updates ES whenever any data is changed in your RMDBS. Look into the API for your platform Elastic Search Client APIhttps://www.elastic.co/guide/en/elasticsearch/client/index.html