Im not familiar with SQLite. Can someone help me with generating random datetime value?
I tried to start with this (its for MS-SQL):
select dateadd(
millisecond,
cast(86400000 * RAND() as int),
convert(time, '00:00')
);
but sqlite returns error: invalid column millisecond.
I need something, that allows to generate random datetime with specified minimum and maximum date, but for now I think just need to know how to convert number to date.
Im using SQLite version 3.7.15.1.
The random() function generates random 64-bit integers.
The strftime() function with the '%s' parameter converts a date/time string into the number of seconds since 1970.
The datetime() function with the 'unixepoch' modifier converts a number of seconds into a date/time string.
To convert the random integer into the desired range of seconds, use the modulo operator (%) with the difference in seconds between the min/max dates as range, and add that to the start date.
For example, the following will generate a random timestamp in Jan 2000:
SELECT datetime(strftime('%s', '2000-01-01 00:00:00') +
abs(random() % (strftime('%s', '2000-01-31 23:59:59') -
strftime('%s', '2000-01-01 00:00:00'))
),
'unixepoch');
Related
I store date from Calendar.getTimeInMilliseconds() in SQLite DB.
I need to mark first rows by every month in SELECT statement, so I need convert time in milliseconds into any date format using SQLite function only. How can I avoid this?
One of SQLite's supported date/time formats is Unix timestamps, i.e., seconds since 1970.
To convert milliseconds to that, just divide by 1000.
Then use some date/time function to get the year and the month:
SELECT strftime('%Y-%m', MillisField / 1000, 'unixepoch') FROM MyTable
Datetime expects epochtime, which is in number of seconds while you are passing in milliseconds. Convert to seconds & apply.
SELECT datetime(1346142933585/1000, 'unixepoch');
Can verify this from this fiddle
http://sqlfiddle.com/#!5/d41d8/223
Do you need to avoid milliseconds to date conversion or function to convert milliseconds to date?
Since sqlite date functions work with seconds, then you can try to
convert milliseconds in your query, like this
select date(milliscolumn/1000,'unixepoch','localtime') from table1
convert millis to seconds before saving it to db, and then use date function in sql query
I was trying to get the count of calls per half-hour interval.
Couldn't figure it out.
select
count(call_id) as '#Calls',
1/2 h(date_time) as 'Call_Interval'
from My_Table
One method to aggregate by various time intervals is with DATEADD and DATEDIFF:
SELECT
COUNT(*) as '#Calls',
DATEADD(minute, (DATEDIFF(minute, '', date_time) / 30) * 30, '') as Call_Interval
FROM dbo.My_Table
GROUP BY DATEADD(minute, (DATEDIFF(minute, '', date_time) / 30) * 30, '')
ORDER BY Call_Interval;
On a side note, the empty string constant above represents the default value for datetime. The default values for datetime and other temporal types are listed below, expressed in ISO 8601 string format:
Data Type
Default Value
date
1900-01-01
datetime
1900-01-01T00:00:00
datetime2
1900-01-01T00:00:00
datetimeoffset
1900-01-01T00:00:00+00:00
smalldatetime
1900-01-01T00:00:00
time
00:00:00
Time interval calculations with a datepart more granular than minute (i.e. second, millisecond, and microsecond) may require a more recent base datetime value than the default value (e.g. 2020-01-01T00:00:00) to avoid overflow.
PreparedStatement psnmt=con.prepareStatement("SELECT (?)-(?) as DiffDate FROM dual");
psnmt.setTimestamp(1,ctenderdate);
psnmt.setTimestamp(2,btenderdate);
ResultSet resrt=psnmt.executeQuery();
if(!resrt.next())
{
out.println("No Records Found");
}
else
{
do
{
datediff=resrt.getString("DiffDate");
}
while(resrt.next());
System.out.println("the no of days Difference"+datediff);
}
ctenderdate=2015-06-27 00:00:00.0
btenderdate=2015-06-29 00:00:00.0
datediff=1 10:18:51.940000000
Expected datediff=2
How to round it off datediff to number of days
EDIT
Subtract TIMESTAMP values
If we really want to subtract two TIMESTAMP values, then we have to work with the INTERVAL DAY TO SECOND datatype that's returned. The easiest way to work with that is to use the EXTRACT function.
If want to return integer number of days (emulating the CEIL function) then we could test whether any part of the time (HOUR, MINUTE, SECOND) was non-zero. If they are all zero, we can use just the DAY portion. Otherwise, we have to add 1 to the DAY portion, and return that.
For example:
SELECT EXTRACT(DAY FROM diff.idts)
+ CASE
WHEN EXTRACT(HOUR FROM diff.idts) > 0
OR EXTRACT(MINUTE FROM diff.idts) > 0
OR EXTRACT(SECOND FROM diff.idts) > 0
THEN 1
ELSE 0
END
AS days_diff
FROM ( SELECT ? - ? AS idts FROM dual ) diff
ORIGINAL ANSWER
For Oracle database, you can perform this operation in the database:
SELECT CEIL(TO_DATE(?,'YYYY-MM-DD HH24:MI:SS.F')-TO_DATE(?,'YYYY-MM-DD HH24:MI:SS.F'))
FROM dual
This assumes the bind parameters are passed as strings, in format that matches the format model specified in the TO_DATE function, for example:
'2015-06-27 14:45:21.0'
(I'm assuming Oracle because of the use of the dual table, and because you are using subtraction operation between two dates. You would need a different statement for a different database.)
To unpack that expression a little bit...
The Oracle TO_DATE function converts a character string into an Oracle DATE value. The second argument is the format model, specifies that format of the first argument.
A subtraction operation between two DATE values returns the difference as a number of days (integer days plus fractional days.)
The CEIL function rounds a non-integer value up to the next higher integer.
FOLLOWUP
Q: how to use it with timestamp?
A: A subtraction of two TIMESTAMP values gets returned as an INTERVAL DAY TO SECOND datatype. And I'd prefer to avoid working with that.
In Oracle, when we do a subtraction of two DATE values, we get a decimal number. That's much easier to work with.
And in terms of "rounding" up a difference in days, I'm fine with disregarding fractional seconds.
If I had to pass in TIMESTAMP values, I would convert them to DATE values. The expressions above are already expecting string values, so I would just replace the ? with
TO_CHAR(?,'YYYY-MM-DD HH24:MI:SS')
If I had a requirement to pass in TIMESTAMP datatype, and return integer days difference rounded up, I would use a query like this:
SELECT CEIL( TO_DATE(TO_CHAR( ? ,'YYYY-MM-DD HH24:MI:SS'),'YYYY-MM-DD HH24:MI:SS')
- TO_DATE(TO_CHAR( ? ,'YYYY-MM-DD HH24:MI:SS'),'YYYY-MM-DD HH24:MI:SS')
) AS days_diff
FROM dual
Check out this link. There are answers for results in hours or minutes. What you are looking for should be similar.
My bad. I should not post just-a-link-answers. What you can do, as described there is:
SELECT TRUNC (SYSDATE) - TO_DATE ('10/20/2012', 'mm/dd/yyyy') FROM DUAL;
Notice the following details:
ENDDATE - STARTDATE will give you a number that corresponds to the
number of days between the two dates.
If you want the result in hours, multiply by 24; if minutes, multiply
by 24*60 and so forth.
You can also convert the result to an INTERVAL. There are two type of
intervals: NUMTODSINTERVAL(ENDDATE - STARTDATE, 'DAY') or
NUMTOYMINTERVAL(ENDDATE - STARTDATE, 'DAY')
We have a timestamp epoch column (BIGINT) stored in Hive.
We want to get Date 'yyyy-MM-dd' for this epoch.
Problem is my epoch is in milliseconds e.g. 1409535303522.
So select timestamp, from_unixtime(timestamp,'yyyy-MM-dd') gives wrong results for date as it expects epoch in seconds.
So i tried dividing it by 1000. But then it gets converted to Double and we can not apply function to it. Even CAST is not working when I try to Convert this double to Bigint.
Solved it by following query:
select timestamp, from_unixtime(CAST(timestamp/1000 as BIGINT), 'yyyy-MM-dd') from Hadoop_V1_Main_text_archieved limit 10;
The type should be double to ensure precision is not lost:
select from_unixtime(cast(1601256179170 as double)/1000.0, "yyyy-MM-dd hh:mm:ss.SSS") as event_timestamp
timestamp_ms is unixtime in milliseconds
SELECT from_unixtime(floor(CAST(timestamp_ms AS BIGINT)/1000), 'yyyy-MM-dd HH:mm:ss.SSS') as created_timestamp FROM table_name;
In the original answer you'll get string, but if you'd like to get date you need to call extra cast with date:
select
timestamp,
cast(from_unixtime(CAST(timestamp/1000 as BIGINT), 'yyyy-MM-dd') as date) as date_col
from Hadoop_V1_Main_text_archieved
limit 10;
Docs for casting dates and timestamps. For converting string to date:
cast(string as date)
If the string is in the form 'YYYY-MM-DD', then a date value corresponding to that year/month/day is returned. If the string value does not match this formate, then NULL is returned.
Date type is available only from Hive > 0.12.0 as mentioned here:
DATE (Note: Only available starting with Hive 0.12.0)
I am storing a timestamp field in a SQLite3 column as TIMESTAMP DATETIME DEFAULT CURRENT_TIMESTAMP and I was wondering if there was any way for it to include milliseconds in the timestamp as well?
Instead of CURRENT_TIMESTAMP, use (STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW')) so that your column definition become:
TIMESTAMP DATETIME DEFAULT(STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW'))
For example:
CREATE TABLE IF NOT EXISTS event
(when_ts DATETIME DEFAULT(STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW')));
To get number of milliseconds since epoch you can use julianday() with some additional calculations:
-- Julian time to Epoch MS
SELECT CAST((julianday('now') - 2440587.5)*86400000 AS INTEGER);
The following method doesn't require any multiplies or divides and should always produce the correct result, as multiple calls to get 'now' in a single query should always return the same result:
SELECT strftime('%s','now') || substr(strftime('%f','now'),4);
The generates the number of seconds and concatenates it to the milliseconds part from the current second+millisecond.
Here's a query that will generate a timestamp as a string with milliseconds:
select strftime("%Y-%m-%d %H:%M:%f", "now");
If you're really bent on using a numeric representation, you could use:
select julianday("now");
The accepted answer only gives you UTC. If you need a local time instead of UTC, use this:
strftime('%Y-%m-%d %H:%M:%f', 'now', 'localtime')