I'm new in PostgreSQL I need to convert the minute's value in a column into hours and minutes format I have searched in various sources but failed to achive.Some one please help me to achieve this.
In mean while I try to use to_char() as follows :
UPDATE tablename SET col2 = TO_CHAR(((col1*60 ||`second`))::interval, ‘HH24:MI:SS’) where id = 145;
but I get the following error...
column "late_by" is of type timestamp with time zone but expression is of type text
LINE 2: UPDATE attendance SET late_by = TO_CHAR(((lateby*60 || 'seco...
^
HINT: You will need to rewrite or cast the expression.
It is unclear what type each column in your statement is.
But if it helps, you can perform maths on intervals
select interval '60 seconds' * 15;
or in your case, if "col1" is integer: interval '60 seconds' * col1;
your column late_by is of time timestamp, yet you want to update it with interval, not timestamp. If you want to save how much time somebody is late, better use interval, eg:
t=# create table w3 (t interval);
CREATE TABLE
t=# insert into w3 select (185||' seconds')::interval;
INSERT 0 1
t=# select * from w3;
t
----------
00:03:05
(1 row)
as you can see "conversion" to minutes done by postgres itself
Related
I want to find the latest value of a column for particular time duration(1 minute in my case) from Kusto table.
I have timeseries data in PostgreSQL table and I am using last() function (https://docs.timescale.com/api/latest/hyperfunctions/last/)to find the latest value of scaled_value for 1 minute time bucket of PostgreSQL and I want to use same function in Kusto Table to get the latest value of scaled_value . What will be correct function to use in Kusto corresponding to last() function in Postgresql
Code I am using in PostgreSQL :
SELECT CAST(EXTRACT(EPOCH FROM time_bucket('1 minutes', timestamp) AT TIME ZONE 'UTC') * 1000 AS BIGINT) as timestamp_epoch,
vessel_telemetry.timeSeries,
last(vessel_telemetry.scaled_value, vessel_telemetry.timestamp) as scaled_value,
FROM shipping.vessel_telemetry
WHERE vessel_telemetry.ingested_timestamp >= '2022-07-20T10:10:58.71Z' AND vessel_telemetry.ingested_timestamp < '2022-07-20T10:15:33.703985Z'
GROUP BY time_bucket('1 minutes', vessel_telemetry.timestamp), vessel_telemetry.vessel_timeSeries
Corresponding code I am using in ADX
VesselTelemetry_DS
| where ingested_timestamp >= datetime(2022-07-20T10:10:58.71Z) and ingested_timestamp < datetime(2022-07-20T10:15:33.703985Z)
| summarize max_scaled_value = max(scaled_value) by bin(timestamp, 1m), timeSeries
| project timestamp_epoch =(datetime_diff('second', timestamp, datetime(1970-01-01)))*1000, timeSeries, max_scaled_value
The data that i am getting using PostgreSQL is not matching with the data I am getting from ADX Query. I think the functionality of last() function of Postgre is different from max() function of ADX. Is there any function in ADX that we can use to perform same as last() of PSQL
arg_max()
arg_max (ExprToMaximize, * | ExprToReturn [, ...])
Please note the order of the parameters, which is opposite to Timescale's last() -
First the expression to maximize, in your case timestamp and then the expression(s) to return, in your case scaled_value
I have a big table in a postgres db with location of units. Now I need to retrieve a location for every 60 seconds.
In Mysql, this is a piece of cake: select * from location_table where unit_id = '123' GROUP BY round(timestamp / 60)
But in postgres this seems to be a very hard problem. I also have the timestamps in dateformat rather than in epoch format.
Here is an example of how the table looks
CREATE TABLE location_table (
unit_id int,
"timestamp" timestamp(3) without time zone NOT NULL,
lat double precision,
lng double precision
);
Use date_trunc() to make sets per minute:
SELECT * -- most likely not what you want
FROM location_table
WHERE unit_id = 123 -- numbers don't need quotes '
GROUP BY date_trunc('minute', 'timestamp');
The * is of course wrong, but I don't know what you want to know about the GROUP so I can't come up with something better.
Edit:
When you need a random result from your table, DISTINCT ON () could do the job:
SELECT DISTINCT ON(date_trunc('minute', timestamp))
* -- your columns
FROM location_table;
There are other (standard SQL) solutions as well, like using row_number().
i have a table where my date/time is of form: 2020-03-10 22:54:08
This is a timestampped object. I tried the following query but didn't return any rows:
select ts from table1
where cast(ts as timestamp) = '2020-03-10 22:54:08'
returns nothing.
How do i query based on date and time in postgressql?
A timestamp has microsecond resolution, so you have to use same techiques as when testing floating point numbers: Round it or use only < and > for comparison.
To retrieve data from a database, you need to refer to SQL SELECT syntax. In your situation, the ts column is already a timestamp, so there is no need to use cast(). Bear in mind, however, that a timestamp type contains fractions of a second (i.e., 2020-03-10 22:54:03.xxx), so you would be better off using a comparison operator (>,<,>=,or <=)
You can retrieve all columns by using the * syntax:
select *
from my_table
where ts >= '2020-03-10 22:54:08';
tymestamp type by default contains also microseconds, so, now() which, for example, is 2020-03-11 01:56:27.593985 here obviously is not equal to 2020-03-11 01:56:27. If you do not want to have microseconds precision in your data then declare your field like ts timestamp(0) NOT NULL DEFAULT now() which means "0 decimal digits for microseconds":
select
current_timestamp::timestamp as ts,
current_timestamp::timestamp(2) as ts2,
current_timestamp::timestamp(0) as ts0;
ts | ts2 | ts0
---------------------------+------------------------+---------------------
2020-03-11 02:02:52.98298 | 2020-03-11 02:02:52.98 | 2020-03-11 02:02:53
Actually this worked.
select distinct(ts) from my_table where ts >= '2020-03-10 22:54:08' and ts <= '2020-03-10 22:54:09'
But this doesn't give me the whole rows
But then i tried this and this worked:
select ts from table1
where to_char(ts,'YYYY-MM-DD HH24:MI:SS') = '2020-03-10 22:54:08'
So I have a string time column in a table and now I want to change that time to date time type and then query data for selected dates.
Is there a direct way to do so? One way I could think of is
1) add a new column
2) insert values into it with converted date
3) Query using the new column
Here I am stuck with the 2nd step with INSERT so need help with that
ALTER TABLE "nds".”unacast_sample_august_2018"
ADD COLUMN new_date timestamp
-- Need correction in select statement that I don't understand
INSERT INTO "nds".”unacast_sample_august_2018” (new_date)
(SELECT new_date from_iso8601_date(substr(timestamp,1,10))
Could some one help me with correction and if possible a better way of doing it?
Tried other way to do in single step but gives error as Column does not exist new_date
SELECT *
FROM (SELECT from_iso8601_date(substr(timestamp,1,10)) FROM "db_name"."table_name") AS new_date
WHERE new_date > from_iso8601('2018-08-26') limit 10;
AND
SELECT new_date = (SELECT from_iso8601_date(substr(timestamp,1,10)))
FROM "db_name"."table_name"
WHERE new_date > from_iso8601('2018-08-26') limit 10;
Could someone correct these queries?
You don't need those steps, just use USING CAST clause on your ALTER TABLE:
CREATE TABLE foobar (my_timestamp) AS
VALUES ('2018-09-20 00:00:00');
ALTER TABLE foobar
ALTER COLUMN my_timestamp TYPE timestamp USING CAST(my_timestamp AS TIMESTAMP);
If your string timestamps are in a correct format this should be enough.
Solved as follows:
select *
from
(
SELECT from_iso8601_date(substr(timestamp,1,10)) as day,*
FROM "db"."table"
)
WHERE day > date_parse('2018-08-26', '%Y-%m-%d')
limit 10
I need to include EXTRACT() function within WHERE clause as follow:
SELECT * FROM my_table WHERE EXTRACT(YEAR FROM date) = '2014';
I get a message like this:
pg_catalog.date_part(unknown, text) doesn't exist**
SQL State 42883
Here is my_table content (gid INTEGER, date DATE):
gid | date
-------+-------------
1 | 2014-12-12
2 | 2014-12-08
3 | 2013-17-15
I have to do it this way because the query is sent from a form on a website that includes a 'Year' field where users enter the year on a 4-digits basis.
The problem is that your column is of data type text, while EXTRACT() only works for date / time types.
You should convert your column to the appropriate data type.
ALTER TABLE my_table ALTER COLUMN date TYPE date;
That's smaller (4 bytes instead of 11 for the text), faster and cleaner (disallows illegal dates and most typos).
If you have non-standard format add a USING clause with a conversion expression. Example:
Alter character field to date
Also, for your queries to be fast with a plain index on date you should rather use sargable predicates. Like:
SELECT * FROM my_table
WHERE date >= '2014-01-01'
AND date < '2015-01-01';
Or, to go with your 4-digit input for the year:
SELECT * FROM my_table
WHERE date >= to_date('2014', 'YYYY')
AND date < to_date('2015', 'YYYY');
You could also be more explicit:
to_date('2014' || '0101', 'YYYYMMNDD')
Both produce the same date '2014-01-01'.
Aside: date is a reserved word in standard SQL and a basic type name in Postgres. Don't use it as identifier.
This happens because the column has a text or varchar type, as opposed to date or timestamp. This is easily reproducible:
SELECT 1 WHERE extract(year from '2014-01-01'::text)='2014';
yields this error:
ERROR: function pg_catalog.date_part(unknown, text) does not exist
LINE 1: SELECT 1 WHERE extract(year from '2014-01-01'::text)='2014';
^ HINT: No function matches the given name and argument types. You might need to add explicit type casts.
extract or is underlying function date_part does not exist for text-like datatypes, but they're not needed anyway. Extracting the year from this date format is equivalent to getting the 4 first characters, so your query would be:
SELECT * FROM my_table WHERE left(date,4)='2014';