alter table can be used to add a column to a table.The .schema command can be used to list the columns in a table.

~]$ sqlite3 /path/to/example.db
SQLite version 3.34.1 2021-01-20 14:10:07
Enter ".help" for usage hints.

sqlite> .schema users
CREATE TABLE users (
        id INTEGER NOT NULL,
        date_created DATETIME,
        email VARCHAR(100) NOT NULL,
        password VARCHAR(200) NOT NULL,
        PRIMARY KEY (id),
        UNIQUE (id),
        UNIQUE (email)
);

Here is an example of how to add a column to the table.

AVOID TROUBLE

If you want to set the column as NOT NULL make sure to include a default value such as DEFAULT 1

sqlite> ALTER TABLE users ADD COLUMN new_column VARCHAR(100) NOT NULL DEFAULT 1;

Or like this, as a oneliner command.

~]$ sqlite3 /path/to/example.db "ALTER TABLE users ADD COLUMN new_column VARCHAR(100) NOT NULL DEFAULT 1"

Then you'll probably want to update the value to the newly added column.

sqlite> UPDATE users SET new_column = 'foo' WHERE id = '1';
sqlite> UPDATE users SET new_column = 'bar' WHERE id = '2';