I have a requirement.
I will provide input as date and time.
My Function must return the date and time of that particular location.
But, my db and computer will be at same date and time only
I need in Sql Anywhere
Thanks,
Nirmal
Related
How to use to_date function in oracle-sqldeveloper to convert a string
May 1 2019 12:00 to date datatype? Does Date in SQL store time too,
or it only stores date? I tried using the to_date function with some
format but it always removes the time part.
If the time is not possible in Date datatype what could be a good alternative?
You can convert your date to a string with (assuming 24-hour values, which seems likely as you don't have an AM/PM marker):
to_date('May 1 2019 12:00', 'Mon DD YYYY HH24:MI', 'nls_date_language=English')
The format elements are in the documentation. I've included the optional third argument to to_date() because your month name has to be interpreted in English, regardless of your session settings.
it always removes the time part
Oracle dates always have both date and time parts, even if the time is set to midnight. You're probably seeing the result of that query as '01-MAY-19'.
Dates don't have any intrinsic human-readable format; Oracle uses its own internal representation, which you generally don't need to worry about.
In most clients and IDEs the session NLS_DATE_FORMAT setting is used to display native dates as strings. For historic reasons that still defaults to DD-MON-YY, despite Y2K, during database creation. it can be changed at database level, and sessions will then inherit that. But each session can override it, e.g. by issuing:
alter session set nls_date_format = 'YYYY-MM-DD HH24:MI:SS'
You can also explicitly convert a date value back to a string, and specify which format elements you want to include, via a to_char() call. Only do that when displaying a value - if you're storing dates or passing them around to functions, always do that as the proper date data type, not as strings. (If you have to pass them outside the database as strings, e.g. to a remote API, you'd usually want to use an ISO-8601 format).
db<>fiddle showing the default output, explicitly formatted as a string (again, for display only - do not store or manipulate dates as string), and with the session format modified.
In SQL Developer you can also go to Tools->Preferences->Database->NLS and change the 'Date format' there - that setting will then apply when you create new sessions, without having to issue alter session each time.
Let's say that I need to create 'chat-like' system. Of course I need to deal with dates somehow.
I read about it a lot and I have some knowledge but I really don't know how to use it.
I would like to store message date in UTC (postgres 12)
Each user should be able to select his time zone and this time zone should be saved into database (standard approach)
When message is retrieved from database I need to convert message date into valid local date based on user selected timezone.
This is really all I need to do and here problem starts:
In postgres date is stored with offset f.e 2020-05-01 00:00:00+02, but I want to store timezone in another table, not here
How can I store user timezone? I should use names like "EST5EDT" or use time offsets as integer?
Where can I find list of all timezones to present user? (Each global website f.e. facebook has list of timezones with offsets, where can I find list of all valid timezones?)
How can I select date with user appropriate timezone? f.e.
SELECT convert_to_user_date("Date", "timezonename??")
FROM "Messages"
Is this correct way to achieve my goal?
These days you don't have to resort to UTC. You can store full timestamps with time zone. This way e.g. you won't lose DST status at the moment the timestamp was recorded in the database.
https://www.postgresql.org/docs/current/datatype-datetime.html
You can easily select the timestamp stored with any time zone shifted to target user's time zone (assuming it's stored somewhere in user preferences). The syntax is SELECT ... AT TIME ZONE
https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-ZONECONVERT
You are very close to a workable setup.
First, use timestamp or timestamp without timezone column data type to store those UTC date/time stamps.
Second, store your users' preferred time zones in varchar(63) columns in the form Asia/Kolkata or America/Halifax.
Third, use postgresql's built in view pg_timezone_names to get a list of valid time zones. You can use it to populate a pulldown list of choices in your user-settings screen.
If you have time for some real excellence in your user-settings screen, you can suggest time zone settings you guess from the users' ip adresses and allow them to change them if your guess was wrong. Read this. How to get Time Zone through IP Address in PHP
Then, when your application starts using postgresql on behalf of any user, look up that user's chosen time zone in your users table, and use it in this SQL command. SET TIME ZONE 'America/Halifax'; (whatever the user's choice is).
Then when you retrieve your time stamps, they will be rendered in the user's local time, and when you store the they'll be in UTC.
The 'toobz are full of advice about this. Here's something that might be useful. How to get Time Zone through IP Address in PHP
Use the data type timestamp with time zone. Don't be worried by the name — that data type really represents an absolute point of time and does not store time zone information.
The only thing you have to do is to set the timezone parameter correctly for the time zone of the client connection, then the value will be represented correctly in that time zone. PostgreSQL does all the work for you.
If you don't like the string representation (e.g., you are disturbed by the time zone offset displayed), use to_char to format the output the way you like:
CREATE TABLE dates (x timestamp with time zone NOT NULL);
SET timezone = 'Europe/Vienna';
INSERT INTO dates VALUES ('2020-06-01 03:00:00');
SET timezone = 'Asia/Kolkata';
SELECT to_char(x, 'YYYY-MM-DD HH24:MI:SS') FROM dates;
to_char
---------------------
2020-06-01 06:30:00
(1 row)
Is there a way to store a date in a PostgreSQL db using the Ethiopian date format? I'm trying to store 29th or 30th of February but it throws an error, because in the Julian calendar there's no such thing. Any inputs?
I am not sure that I'll tell you something new but...
Databases are used by programs or by interfaces, I never saw databases that are used by end-user in console with psql.
If you are develop an application, that must display dates in specific calendar, you can store date in PostgreSQL in TIMESTAMP. All operations with dates will work correct in database. But you have to implement conversion from TIMESTAMP into string representation and vice versa in your application manually. If this is most important thing for your application, you will do this.
All queries that must return date you will write with conversion into DOUBLE PRECISION e.g.
SELECT EXTRACT(EPOCH FROM timestamp_field)
This returns DOUBLE PRECISION value that represents timestamp in numerical format.
All date parameters in queries you have convert from numerical presentation in TIMESTAMP using built-in function to_timestamp:
update table_name set
timestamp_fileld = to_timestamp(1384852375.46666)
The other solution is to write psql functions that do this for you directly in queries, but anyway you need to handle each input/output of date fields in queries.
I have a requirement to disregard records from the DB that are more than 10 minutes old. However, the DB server is present in a different time zone than the app server. I tried to leverage the time zone details from the timestamp column value but it seems that they do not store the time zone details in that column value (bad design?). However, i have found a way to get this information for the DB instance using a query:
select dbtimezone from dual.
However, most of the implementations in java support time zones via names and not offset information. I need to be able to translate this offset exactly to a timezone (EST etc) so that i may not miss any DST related time in my calculations. like so:
TimeZone dbZone = TimeZone.getTimeZone(10000); // offset is +10000
Calendar cal = Calendar.getInstance(dbZone);
cal.setTime(new Date());
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
df.setTimeZone(dbZone);
Date parsedDate = df.parse(df.format(cal.getTime()));
The plan is to convert the present client/app time to the DB specific timezone time and perform the difference between the two.
This cannot be done in a query due to some restraints. Please do not ask me to write a query to get latest records etc. Must be done in Java.
Any tips?
I am guessing it might get you in the right direction. You can try the following so you know the offset from EST and can do the calculation accordingly:
SELECT TZ_OFFSET('US/Eastern') FROM DUAL;
So a return of -3:00 would mean it is PST time. Maybe you've already tried this?
I am trying to execute the following query
INSERT INTO hotspot(timestamp) VALUES
(timestamp with time zone '2012-10-25 14:00:00 +05:00' at time zone 'EET');
and i want to pass the timestamp as a variable.
My timestamp column is type of timestamp with time zone.
Do you have any idea how this can be done?
When i do... (Java, Postgresql)
String stm= "INSERT INTO hotspot(timestamp) VALUES(timestamp with time zone ? at time zone 'EET')";
pst = con.prepareStatement(stm);
pst.setString(1, "2012-08-24 14:00:00 +05:00");
pst.executeUpdate();
I get a syntax error at or near "$1"
Is there anyway i can overcome this error??
Thank you in advance!!
Update: I tried to use the setTimestamp by the following way...
Calendar c=Calendar.getInstance(TimeZone.getTimeZone("GMT+05:00"));
String stm= "INSERT INTO hotspot(timestamp) VALUES(?)";
pst = con.prepareStatement(stm);
pst.setTimestamp(1,Timestamp.valueOf("2012-01-05 14:00:00"), c );
pst.executeUpdate();
I suppose that the correct value in the DB should be (regarding that my local time zone is EET (+02))
2012-01-05 11:00:00 +02
but using pgadmin i check the value and i get
2012-01-05 14:00:00 +02
Any suggestions?
Consider using the setTimestamp() method instead of setString() method. Check this link in order to understand how to use PreparedStatement.
Edit: As I explained in the comment, check the API reference for setTimestamp() with three parameters:
Sets the designated parameter to the given java.sql.Timestamp value,
using the given Calendar object. The driver uses the Calendar object
to construct an SQL TIMESTAMP value, which the driver then sends to
the database. With a Calendar object, the driver can calculate the
timestamp taking into account a custom timezone. If no Calendar object
is specified, the driver uses the default timezone, which is that of
the virtual machine running the application.
Federico Cristina is quite right that setTimestamp is the correct way to do this.
The reason for the syntax error is that you can't specify the type with a leading type-specifier when passing a parameter. The INTEGER '4' style is only valid for literals, not parameters.
Your code will be PREPAREd then EXECUTEd at the protocol level. Here's what happens if I PREPARE it:
regress=> PREPARE blah(timestamptz) AS INSERT INTO hotspot(timestamp) VALUES(timestamp with time zone $1 at time zone 'EET');
ERROR: syntax error at or near "$1"
LINE 1: ...otspot(timestamp) VALUES(timestamp with time zone $1 at time...
Since the data type is specified in the query parameter you can omit it, writing instead:
String stm= "INSERT INTO hotspot(\"timestamp\") VALUES(? at time zone 'EET')";
Note that I've double-quoted "timestamp" as well, because it's a reserved word. It'll work without quotes in some contexts but not others. Choosing a data type name or reserved word as a column name is generally a bad idea.