Question: I have four columns of contact namely `contact1`, `contact2`, `contact3`, `contact4`.
How to write sql to get unique contacts from 4 contacts?

```
contact1   contact2   contact3   contact4
8888498756 8888498756 8888498756 8888498756

```

These are four same contacts how to get unique only in sql.

```
select ca.propno, ca.contact1, ca.contact2, ca.mobile1, ca.mobile2
from BIUSR.tbl_trn_customer_address ca
where ca.contact1 not in (ca.contact2, ca.mobile1, ca.mobile2)

```

Answer: 
Take a look at this package for React Native <https://github.com/peterp/react-native-tags> it should solve your problem, and it is easy to implement
there are a lot of libraries to help with a few use cases. If it's minor we can build our own logic but if you want many things cover you can go with the libraries and later contribute to them.

One such library for your use case is this: <https://github.com/prakhar1989/react-tags#readme>