RE: How to avoid the null value in the field
Hi James,
You can update this existing records with default value of this two options field.
Two ways you can try to test.
1.Export then import records after update.
(1) Choose your entity(Doctors) with help of a view and Click on Export to Excel.

(2) Open the download excel and changes field that you want.
Fill Two option field column that is null with default value ‘No’ in excel.
(3) Save the excel.
(4) Click on Import.

(5) Choose excel.

(6) click Next and Finish button.


However, this way you need change value manually, it is just suitable for a small amount of records.so you can use flow to change huge records.
2.create an instant flow to update records.
(1) create and name an instant flow.

(2) Select Common Data service connector and select List records as an action.

(3) Add the Filter Query from Advanced options.
Filter Query : Field that type is Two options is null.

(4) choose update a record action and set the two options field value to ‘No’.


(5) Click Save and Test button.

(6) Test Results.


Regards,
Clofly