SQL: Subtracting 1 day from a timestamp date

I am using Datagrip for Postgresql. I have a table with a date field in timestamp format (ex: 2016-11-01 00:00:00). I want to be able to:

1. apply a mathematical operator to subtract 1 day
2. filter it based on a time window of today-130 days
3. display it without the hh/mm/ss part of the stamp (2016-10-31)

Current starting query:

select org_id, count(accounts) as count, ((date_at) - 1) as dateat from sourcetable where date_at <= now() - 130 group by org_id, dateat 

The ((date_at)-1) clause on line 1 results in:

[42883] ERROR: operator does not exist: timestamp without time zone - integer Hint: No operator matches the given name and argument type(s). You might need to add explicit type casts. Position: 69

The now() clause spawns a similar message:

[42883] ERROR: operator does not exist: timestamp with time zone - integer Hint: No operator matches the given name and argument type(s). You might need to add explicit type casts. Position: ...

Online guides to type casts are singularly unhelpful. Input is appreciated.

2 Answers

Use the INTERVAL type to it. E.g:

--yesterday SELECT NOW() - INTERVAL '1 DAY'; --Unrelated: PostgreSQL also supports some interesting shortcuts: SELECT 'yesterday'::TIMESTAMP, 'tomorrow'::TIMESTAMP, 'allballs'::TIME AS aka_midnight; 

You can do the following then:

SELECT org_id, count(accounts) AS COUNT, ((date_at) - INTERVAL '1 DAY') AS dateat FROM sourcetable WHERE date_at <= now() - INTERVAL '130 DAYS' GROUP BY org_id, dateat; 

TIPS

Tip 1

You can append multiple operands. E.g.: how to get last day of current month?

SELECT date_trunc('MONTH', CURRENT_DATE) + INTERVAL '1 MONTH - 1 DAY'; 

Tip 2

You can also create an interval using make_interval function, useful when you need to create it at runtime (not using literals):

SELECT make_interval(days => 10 + 2); SELECT make_interval(days => 1, hours => 2); SELECT make_interval(0, 1, 0, 5, 0, 0, 0.0); 

More info:

Date/Time Functions and Operators

datatype-datetime (Especial values).

You can cast a TIMESTAMP to a DATE, which allows you to subtract an INTEGER from it.

For instance, to get yesterday:

now()::DATE - 1 

So your query will become:

SELECT org_id, date_at::DATE - 1 AS dateat, COUNT(accounts) AS count FROM sourcetable WHERE date_at <= NOW()::DATE - 130 GROUP BY 1, 2