Is it possible to have permissioned data access? Suppose I am having a multi_index table and whoever adds data to that table only can access the data because I am having a table storage and one account named "myaccount" has added an entry but everyone else can access that data by doing cleos get table? Is there any way to change this or any other way to achieve permissioned data access?
I don't think that it is possible to have permissioned tables.Because as you are calling cleos get table but you are not giving any authorization to call this table query.So, i suggest to not to keep any private data in tables. For more see this Can we add the permission to access the table?
Is it possible to have permissioned data access?
No, not natively.
Is there any way to change this or any other way to achieve permissioned data access?
As suggested by others, the only way to keep some form of permissioned data on the blockchain is by only storing encrypted data. If you're worried about encryption / decryption resource consumption, you can perform these processes off-chain. This post shows a code example and a brief explanation of the process you could use.
See a list of different "permission models" here, how to encrypt private data in a public database:
Even though it is BigChainDb, the principles apply across all blockchains.