How to add default value in SQLite?

Looks good to me. Here are the Docs.

sqlite> create table t1 (id INTEGER PRIMARY KEY, name TEXT, created DATE);
sqlite> .table
t1
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t1 (id INTEGER PRIMARY KEY, name TEXT, created DATE);
COMMIT;

sqlite> alter table t1 add column status varchar default 'N';
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t1 (id INTEGER PRIMARY KEY, name TEXT, created DATE, status varchar default 'N');
COMMIT;

sqlite> insert into t1 (name) values ("test");
sqlite> select * from t1;
1|test||N

Dump your schema and verify that your table structure is there after calling ALTER TABLE but before the INSERT. If it’s in a transaction, make sure to COMMIT the transaction before the insert.

$ sqlite3 test.db ".dump"