查找当天给出的第一个第二个时间戳

I have a date format like '2016-09-21'. What I want to achieve is given that day find the first second of the first day of the current month (current year).

I want to do this because a have a MySQL column with a DATETIME format. So I want to SELECT all records of the current month.

You can use SQL to get all records of the current month:

select * from your_table
where year(curdate()) = year(datecolumn)
and month(curdate()) = month(datecolumn)

From: mysql query to select all rows of current month?