NOW() : Current Date & Time in MySQL

SELECT NOW(); 

20160917165099.000000

SELECT NOW()- interval 1 HOUR  as One_hour_back,
 NOW() as Present, 
 NOW()+ interval 1 HOUR as One_hour_After

Yesterday & Tomorrow date by using NOW()

SELECT NOW()- interval 1 day  as Yesterday, 
NOW() as Today, 
NOW()+ interval 1 day as Tomorrow

Queries using Date and Time

Last Month , Today and Next Month

SELECT NOW()- interval 1 month  as LastMonth, 
NOW() as Today, 
NOW()+ interval 1 Month as NextMonth

Matching only date part ( not time ) with datetime field or Now()

SELECT * from table_name WHERE DATE(date_column)='2019-12-26'

SELECT * from table_name WHERE DATE(date_column)=CURDATE()

Read more on CURDATE()

Adding current date and time by default to a record.