SQL Get Current Date

Databases allow you to compare a column or result set against today's current date.
PostgreSQL, MySQL, Oracle
SQL Server
select * from rent_payments where payment_date < current_date;

Assume that we run this query on March 5th, 2018 (3/5/2018).

rent_payments table

id payment_date dollar_amount
1 3/1/2018 2000
2 3/2/2018 1500
3 3/1/2018 1800
4 3/3/2018 1900
5 4/2/2018 2000
6 4/2/2018 1900

Query results

id payment_date dollar_amount
1 3/1/2018 2000
2 3/2/2018 1500
3 3/1/2018 1800
4 3/3/2018 1900