After performing the following:
INSERT INTO times_table (start_time, end_time) VALUES (to_date('2/3/2016 12:05',
'MM/DD/YYYY HH24:MI'), to_date('2/3/2016 15:05', 'MM/DD/YYYY HH24:MI'));
PostgreSQL only displays the date.
If possible, would I have to run a separate select statement to extract the time (i.e. 12:05 and 15:05), stored in that field? Or are the times completey discard when the query gets executed.
I don't want to use timestamp, since I'd like to execute this in Oracle SQL as well.
to_date returns... a date. Surprise! So yeah, it's not going to give you the time.
You should be using the timestamp data type to store times and functions which return timestamps. So use to_timestamp.
Oracle also has a timestamp data type and to_timestamp function.
In general, trying to write one set of SQL that works with multiple databases results in either having to write very simple SQL that doesn't take advantage of any of the database's features, or madness.
Instead, use a SQL query builder to write your SQL for you, take care of compatibility issues, and allow you to add clauses to existing statements. For example, Javascript has Knex.js and Perl has SQL::Abstract.
Related
In my PostgreSQL database I have a daterange type where they are all of a format like so: [2017-08-01,2018-01-27). I'm trying to figure out a way to identify all elements where the entire range occurs in the past. Basically I need to do cleanup, so I'm wanting a DELETE FROM type statement.
Use the function upper():
delete from my_table
where upper(my_column) <= current_date;
I have a table on PostgreSQL with a field named data that is jsonb with a lot of objects, I want to make an index to speed up the queries. I'm using few rows to test the data (just 15 rows) but I don't want to have problems with the queries in the future. I'm getting data from the Twitter API, so with a week I get around 10gb of data. If I make the normal index
CREATE INDEX ON tweet((data->>'created_at'));
I get a text index, if I make:
Create index on tweet((CAST(data->>'created_at' AS timestamp)));
I get
ERROR: functions in index expression must be marked IMMUTABLE
I've tried to make it "inmutable" setting the timezone with
date_trunc('seconds', CAST(data->>'created_at' AS timestamp) at time zone 'GMT')
but I'm still getting the "immutable" error. So, How can I accomplish a timestamp index from a JSON? I know that I could make a simple column with the date because probably it will remain constant in the time, but I want to learn how to do that.
This expression won't be allowed in the index either:
(CAST(data->>'created_at' AS timestamp) at time zone 'UTC')
It's not immutable, because the first cast depends on your DateStyle setting (among other things). Doesn't help to translate the result to UTC after the function call, uncertainty has already crept in ...
The solution is a function that makes the cast immutable by fixing the time zone (like #a_horse already hinted).
I suggest to use to_timestamp() (which is also only STABLE, not IMMUTABLE) instead of the cast to rule out some source of trouble - DateStyle being one.
CREATE OR REPLACE FUNCTION f_cast_isots(text)
RETURNS timestamptz AS
$$SELECT to_timestamp($1, 'YYYY-MM-DD HH24:MI')$$ -- adapt to your needs
LANGUAGE sql IMMUTABLE;
Note that this returns timestamptz. Then:
CREATE INDEX foo ON t (f_cast_isots(data->>'created_at'));
Detailed explanation for this technique in this related answer:
Does PostgreSQL support "accent insensitive" collations?
Related:
Query on a time range ignoring the date of timestamps
In my table results from column work_time (interval type) display as 200:00:00. Is it possible to cut the seconds part, so it will be displayed as 200:00? Or, even better: 200h00min (I've seen it accepts h unit in insert so why not load it like this?).
Preferably, by altering work_time column, not by changing the select query.
This is not something you should do by altering a column but by changing the select query in some way. If you change the column you are changing storage and functional uses, and that's not good. To change it on output, you need to modify how it is retrieved.
You have two basic options. The first is to modify your select queries directly, using to_char(myintervalcol, 'HH24:MI')
However if your issue is that you have a common format you want to have universal access to in your select query, PostgreSQL has a neat trick I call "table methods." You can attach a function to a table in such a way that you can call it in a similar (but not quite identical) syntax to a new column. In this case you would do something like:
CREATE OR REPLACE FUNCTION myinterval_nosecs(mytable) RETURNS text LANGUAGE SQL
IMMUTABLE AS
$$
SELECT to_char($1.myintervalcol, 'HH24:MI');
$$;
This works on the row input, not on the underlying table. As it always returns the same information for the same input, you can mark it immutable and even index the output (meaning it can be run at plan time and indexed used).
To call this, you'd do something like:
SELECT myinterval_nosecs(m) FROM mytable m;
But you can then use the special syntax above to rewrite that as:
SELECT m.myinterval_nosecs FROM mytable m;
Note that since myinterval_nosecs is a function you cannot omit the m. at the beginning. This is because the query planner will rewrite the query in the former syntax and will not guess as to which relation you mean to run it against.
Wondering if there is a way to query a SQL Server database and somehow format columns to omit commas in the data if there is any.
Reason for asking is I have 10000+ records and through out the data the varchar have data like 3,25% and other 1%.
I'd prefer not to alter the data in the original table thus asking if a select with other functions would do the trick.
I have thought about selecting all the data into a temp table and stripping the commas but that is a lot of work for every time I do the query.
Any info or if its is possible please reply.
Take a look at the REPLACE function:
SELECT REPLACE(YourColumn, ',', '')
FROM YourTable
Use SQL REPLACE :
REPLACE(YourField,',','')
I am working on third party data which I need to load into my postgresql database. I am running into problems where sometimes I get the time '24:00:30' when it actually should be '00:00:30'. This rejects the data.
I tried to cast but it did not work.
insert into stop_times_test trip_id, cast(arrival_time as time), feed_id, status
from external_source;
Is there any way to convert to the correct one internally?
This may work for your case:
> select '0:0:0'::time + '24:00:30'::interval;
00:00:30
Cast to interval, then cast to time:
SELECT '24:00:30'::interval::time
If you want to bulk load the data with COPY or mass INSERT make the target column data type interval and convert it to time later. This works out of the box:
ALTER TABLE mytable ALTER col1 TYPE time;
No, there is no magic way of doing it. No cast will help you. 24:00:30 is an invalid time. Period.
You could try adding that value on a varchar and then using regular expressions to update the right values and insert them on the right columns. This sort of things happen a lot when doing data transformation.