Database rules and types

Typically, there are four types of database rules. These rules dictate different responsibilities:

• Read and write rules: As already seen, the .read and .write rule types are utilized to pronounce the conditions under which the data in a Realtime Database might be perused and written by clients.
• Data validation rules: The .validate rule type enables standards to be used that approve data values before they are written to the database. This gives an adaptable approach to guarantee that data sent to the database meets the precise form. This includes ensuring that the data sent to a specific database node is string and does not surpass a particular length, child node limits, and so on. 
• Indexing rules: The .indexOn rule type gives a system by which you, as the application engineer, have database nodes to be indexed, so intern helps you in arranging your child nodes as indexes, and it will help in ordering and querying.