Q:

How to add a boolean datatype column to an existing table in sql?

I have a table called person in my database. I want to add another column to the same table and it's a Boolean datatype column. I have tried following queries but it says syntax error near default. I know this is a common and there are lot of answers. I have tried many of them and couldn't figure out to make it work. So please help me.         
queries I have tried 
ALTER TABLE person add column "AdminApproved" BOOLEAN SET default FALSE;
ALTER TABLE person alter column "AdminApproved" BOOLEAN SET default FALSE;         

I have tried without SET key word too.

A:

In SQL SERVER it is BIT, though it allows NULL to be stored 
ALTER TABLE person add  [AdminApproved] BIT default 'FALSE';

Also there are other mistakes in your query

When you alter a table to add column no need to mention column keyword in alter statement 
For adding default constraint no need to use SET keyword
Default value for a BIT column can be ('TRUE' or '1') / ('FALSE' or 0). TRUE or FALSE needs to mentioned as string not as Identifier 

A:

The answer given by Pரதீப் creates a nullable bool, not a bool, which may be fine for you. For example in C# it would create: bool? AdminApprovednot bool AdminApproved.
If you need to create a bool (defaulting to false):
    ALTER TABLE person
    ADD AdminApproved BIT
    DEFAULT 0 NOT NULL;

