added sql for adding created_at and updated_at code example

Example 1: add created and updatedAt fields in mysql

ALTER TABLE t1
ADD COLUMN createdAt TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
ADD COLUMN updatedAt DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

Example 2: ADD COLOUNS CREATED AND UPDATED AT IN MYSQL

ALTER TABLE t1
ADD COLUMN created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
ADD COLUMN updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;