How to store small database, editable data on blockchain accessible by smart contract?

Question

New to blockchain and smart contracts. Been doing research and I realize I can't update my transaction smart contract. Is it possible to store database data as an entry to the ledger or in another smart contract that only I update that the transaction smart contract can access to pull the data?

For example

User wants to make a donation payment to an organization. His wallet needs to pull in all possible organizations for him to choose from a database which I would like to be decentralized.

Where can I store the organizations and their wallet address as well as update them or remove them? Also I want to add subsections of an organization and its address.

For example

User wallet pulls in:

• Hospital, address
• Hospital, lab, address,
• Hospital, ER, address
• Fire department, address
• Fire department, equipment fund, address
• Fire department, supplies fund, address
• Etc.

I would read the only one adding organizations and removing them . Is there a way to do this all decentralized inside the blockchain?

Chris

Answer 1

Smart contracts can have Arrays and Maps as data structures that store state permanently on the blockchain, and functions of the smart contract can modify them.

For your example, you could use something like this:

pragma solidity ^0.4.16;

contract MyOrgDatabase {
  struct Organization {
    address _where;
    string _name;
  }
  Organization[] public availableOrgs;
  address public owner = msg.sender;

  function addOrg(address _where, string _name) {
    require(msg.sender == owner);
    availableOrgs.push(Organization(_where, _name));
  }
}

That contract has a public availableOrgs property that anyone can read from the blockchain. But only the address that created the contract (the owner) can add organizations to that list (you'd probably also want to add functions for removing organizations from the list, or changing the ownership of the contract for a fully-featured contract, but that should give you the idea).