SQL – Other Things

Comparing PostgreSQL timestamps without timezones with dates with a timezone

Adam Zolo — Thu, 12 Jan 2023 23:04:33 +0000

Problem: you have a timestamp field and you need to compare it with something that has a timezone.

Let’s assume your database default timezone is UTC (can check it with show timezone;). Thus, we are making the assumption that your dates are stored in UTC.

Since timestamp does not have any timezone data, we first need to read it in UTC, so it adds the timezone data. Then we can convert it to the desired timezone:

select timestamp_field AT TIME ZONE 'UTC' AT TIME ZONE 'America/New_York'

Now, we have the timezone and proper daylight-saving offset.

Just for fun, let’s check if the current hour matches the hour from the saved timestamp field in the ‘America/New_York’ timezone:

EXTRACT ( HOUR FROM timestamp_field at time zone 'UTC' at time zone 'America/New_York') = EXTRACT ( HOUR FROM now() at time zone 'America/New_York')

Notice, that we do not read now() in UTC timezone first, because our DB default timezone is UTC and now() already has all of the timezone data.

Getting Min Max ids after splitting SQL table into n equal parts using ntile

Adam Zolo — Wed, 10 Jun 2020 13:11:10 +0000

This will split your_table into 10 equal parts, and give you the minimum and maximum id for each part:

with cte as
(
select
id,
ntile(10) over(order by a.id) as bucket_id
from your_table as a
group by a.id
)

select bucket_id, min(id), max(id)
from cte
group by bucket_id
order by bucket_id

Removing Duplicate Data from SQL Query Caused by New Line Character

Adam Zolo — Mon, 16 Sep 2013 21:08:03 +0000

We had a query retrieving data from a linked Oracle server. We needed unique rows only. This is the original query:

SELECT Column
     FROM OPENQUERY( LinkedServer, 'SELECT DISTINCT Column from TABLE;' );

However, this still returned some duplicates despite using DISTINCT. As it turned out, some rows had a new line character in them. The solution:

SELECT distinct replace(replace(Column,CHAR(13),''),CHAR(10),'')
     FROM OPENQUERY( LinkedServer, 'SELECT DISTINCT Column from TABLE;' )