I have searched for this but found nothing even relevant to answer my question. My doubt is like we know that max size for a varchar2 data type is 32767 bytes so on similar lines how much space is allocated to store a value of date data type. Is it treated like the varchar2 data type? such that the size will depend on number of characters? or is it something different.
Thanks
From the documentation:
The database stores dates internally as numbers. Dates are stored in fixed-length fields of 7 bytes each, corresponding to century, year, month, day, hour, minute, and second.
So a date is always 7 bytes. Timestamps are longer (11 bytes) to hold the additional precision, and adding time zone increases that further (to 13 bytes). You can see that if you dump a value:
create table t42 (d date, t timestamp);
insert into t42 (d, t) values (sysdate, systimestamp);
column dumpd format a40
column dumpt format a60
select dump(d) as dumpd, dump(t) as dumpt
from t42;
DUMPD DUMPT
---------------------------------------- ------------------------------------------------------------
Typ=12 Len=7: 120,114,3,21,12,30,11 Typ=180 Len=11: 120,114,3,21,12,30,11,17,32,145,56
Related
TRANSACTION_DATE is a DATE data type.
This code lists all of the event dates to the MI:SSSS.
select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS') as trans_date from ticket_orders;
Now I want to get counts for those dates and I get ORA-00979 not a GROUP BY function.
select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS') as trans_date,
count(*)
from ticket_orders
group by to_char(transaction_date,'YYYY-MON-DD HH24:MI:SSSS');
ERROR ORA-00979: not a GROUP BY expression
How do I get a count of transactions to the MI:SSSS precision?
A DATE data type is a binary data type that is composed of 7 bytes representing century, year-of-century, month, day, hour, minute and second. It ALWAYS has those components and it NEVER contains fractional seconds (that is for the TIMESTAMP data type which can have fractional seconds and/or time zone information).
If DATE type does not store fractional seconds, why does a typical row from my first query look like this 2021-FEB-25 07:58:2626
That is because you are displaying the seconds twice as you use the SS format model for seconds twice.
Your query can just be:
select to_char(transaction_date,'YYYY-MON-DD HH24:MI:SS') as trans_date,
count(*)
from ticket_orders
group by
transaction_date;
db<>fiddle here
The DATE data type does not store fractional seconds. You can reference the Oracle documentation about data types.
DATE
Valid date range from January 1, 4712 BC, to December 31, 9999 AD. The
default format is determined explicitly by the NLS_DATE_FORMAT
parameter or implicitly by the NLS_TERRITORY parameter. The size is
fixed at 7 bytes. This data type contains the datetime fields YEAR,
MONTH, DAY, HOUR, MINUTE, and SECOND. It does not have fractional
seconds or a time zone.
If you want a data type that stores fractional seconds you will need to use TIMESTAMP
TIMESTAMP [(fractional_seconds_precision)]
Year, month, and day values of date, as well as hour, minute, and
second values of time, where fractional_seconds_precision is the
number of digits in the fractional part of the SECOND datetime field.
Accepted values of fractional_seconds_precision are 0 to 9. The
default is 6. The default format is determined explicitly by the
NLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORY
parameter. The size is 7 or 11 bytes, depending on the precision. This
data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE,
and SECOND. It contains fractional seconds but does not have a time
zone.
I want to store a structure (Activity) with a Months field, the user can select 1 or more months for each activity, but I have to filter in a query by a specific month.
I have 4 approaches to store de data:
I can create a table Activity_month that each row represents the activity with each month selected.
Store in a Varchar2(12), and each month es a unique character.
Store in a NUMBER(2), and each bit is a month, and the selected month is represented with 1, so the bit array 000100000011 represents that April, November, and December were selected.
Create 12 Number(1) columns for each month.
Which one is better for store and search?
It depends on how you will use it this data... Will you use it to filter data? How often? What filters will be most popular? So you need to answer a few questions:
Will you filter data just by one month? ie show me rows for April
Will you filter it as: give me those rows for April and June, but not January and December?
Will you aggregate rows by month?
Store in a NUMBER(2), and each bit is a month, and the selected month is represented with 1, so the bit array 000100000011 represents that April, November, and December were selected.
Create 12 Number(1) columns for each month.
You can use also virtual columns: for example, you can create 12 Number(1) columns and add virtual column
generated as (jan*power(2,11)+feb*power(2,10)+...+dec*power(2,0)).
But, since Number(1) takes 2 bytes, I'd prefer varchar2(1 byte) with check(... in ('Y','N') (or '0','1'):
SQL> select dump(cast(1 as number(1))) dmp_number_1 from dual;
DMP_NUMBER_1
--------------------
Typ=2 Len=2: 193,2
SQL> select dump(cast('Y' as varchar2(1))) dmp_varchar_1 from dual;
DMP_VARCHAR_1
--------------------
Typ=1 Len=1: 89
In this case you can create virtual column generated as (jan||feb||...||dec).
Or even winter as (jan||feb||dec)
Then you will need to decide if you want to create indexes on them.
Umm, Hello, can someone tell me how many bytes takes Date Time format in Oracle SQL pls ?
I tryed to find it with google, but i couldnt find it.
Thank for answer.
You can use DUMP function to retrive information about expression value, like this SELECT DUMP(SYSDATE,10) FROM dual
and it says Typ=13 Len=8: 223,7,4,23,14,17,41,0, so 8 bytes.
From oracle docs
http://docs.oracle.com/cd/B28359_01/server.111/b28286/functions048.htm#SQLRF00635
DUMP returns a VARCHAR2 value containing the datatype code, length in
bytes, and internal representation of expr. The returned result is
always in the database character set.
Aslo, there are two different raw forms for DATEs in Oracle:
https://community.oracle.com/thread/2257401
Type 12 (7 bytes) is used for DATE columns
Type 13 (8 bytes)
is used for other DATE expressions, including DATE literals and results for date arithmetic and functions.
The size of a date time format is fixed at 7 bytes, see Oracle's documentation or alternatively run this:
select vsize(sysdate) from dual
or this:
create table test (dt date);
select data_length from user_tab_columns where table_name = 'ZTEST';
In one field I need to store not a datetime pair, i.e. a standard Oracle date.
01/10/2009 22:10:39
But time only
22:10:39
I think that save disk space (I have 2 million rows) or provide faster processing.
You could try the INTERVAL DAY TO SECOND data type but it won't save you any disk space ... it is very suitable for this purpose though.
create table t1 (time_of_day interval day (0) to second(0));
insert into t1 values (TO_DSINTERVAL('0 23:59:59'));
select date '2009-05-13'+time_of_day
from t1;
11 bytes though.
Your best bet would probably be storing "seconds since midnight" as a number field.
SELECT to_char( SYSDATE, 'SSSSS' ) FROM dual;
You can extract the time from a date as a string like this:
to_char(sysdate,'HH.MI.SS')
but there is no time-only data type that will help you save space.
you can use:
TO_CHAR(<DATE_COLUMN>, '<TIME_FORMAT>');
example
TO_CHAR(SYSDATE, 'HH24:MI:SS');
for time format you can check in here
You would save a few Mb of disk space(which is nothing nowadays) and you would gain next to nothing in performance.
You could use a column of NUMBER type for storing the number of seconds since midnight as suggested, just don't forget about the constraints.
(You'd probably use NUMBER(5, 0) which uses 1-3 bytes depending on the stored value, instead of a constant 7 bytes used by a DATE column)
I have created a table in Oracle in which I have KPI_START_DATE column which is a Date datatype, and KPI_START_TIME which is a TIMESTAMP datatype.
Now I want to modify this date dataype for
KPI_START_DATE to dd/mm/yyyy
and
KPI_START_TIME to HH:MI:SS.
So that user should always enter the date and time in this column in this proper format.
I tried below query but its was giving error:
Alter table KPI_DEFINITION MODIFY(to_char(KPI_START_DATE,'dd/mm/yyyy') )
DATE and TIMESTAMP columns do not have any inherent readable format. The values are stored in Oracle's own internal representation, which has no resemblance to a human-readable date or time. At the point to retrieve or display a value you can convert it to whatever format you want, with to_char().
Both DATE and TIMESTAMP have date and time components (to second precision with DATE, and with fractional seconds with TIMESTAMP; plus time zone information with the extended data types), and you should not try to store them separately as two columns. Have a single column and extract the information you need at any time; to get the information out of a single column but split into two fields you could do:
select to_char(KPI_START, 'dd/mm/yyyy') as KPI_START_DATE,
to_char(KPI_START, 'hh24:mi:ss') as KPI_START_TIME
but you'd generally want both together anyway:
select to_char(KPI_START, 'dd/mm/yyyy hh24:mi:ss')
Also notice the 'hh24' format model to get the 24-hour clock time; otherwise you wouldn't see any difference between 3 a.m. and 3 p.m.
You can store a value in either type of column with the time set to midnight, but it does still have a time component - it is just midnight. You can't store a value in either type of column with just a time component - it has to have a date too. You could make that a nominal date and just ignore it, but I've never seen a valid reason to do that - you're wasting storage in two columns, and making searching for and comparing values much harder. Oracle even provides a default date if you don't specify one (first day of current month). But the value always has both a date and a time part:
create table KPI_DEFINITION (KPI_START date);
insert into KPI_DEFINITION (KPI_START)
values (to_date('27/01/2015', 'DD/MM/YYYY'));
insert into KPI_DEFINITION (KPI_START)
values (to_date('12:41:57', 'HH24:MI:SS'));
select to_char(KPI_START, 'YYYY-MM-DD HH24:MI:SS') from KPI_DEFINITION;
TO_CHAR(KPI_START,'YYYY-MM-DDHH24:MI:SS')
-----------------------------------------
2015-01-27 00:00:00
2015-01-01 12:41:57
Your users should be inserting a single value with both date and time as one:
insert into KPI_DEFINITION (KPI_START)
values (to_date('27/01/2015 12:41:57', 'DD/MM/YYYY HH24:MI:SS'));
select to_char(KPI_START, 'YYYY-MM-DD HH24:MI:SS') from KPI_DEFINITION;
TO_CHAR(KPI_START,'YYYY-MM-DDHH24:MI:SS')
-----------------------------------------
2015-01-27 12:41:57
You can also use date or timestamp literals, and if using to_date() you should always specify the full format - don't rely on NLS settings as they may be different for other users.
You should understand difference between datatype and format. DATE is a datatype. TIMESTAMP is a datatype. None of them have formats, they're just numbers.
When converting character datatype to or from date datatype, format should be applied. It's an attribute of an actual conversion, nothing else.
Look at this:
SQL> create table tmp$date(d date);
Table created
SQL> insert into tmp$date values (DATE '2010-11-01');
1 row inserted
SQL> insert into tmp$date values (DATE '2014-12-28');
1 row inserted
SQL> select d, dump(d) from tmp$date;
D DUMP(D)
----------- ---------------------------------
01.11.2010 Typ=12 Len=7: 120,110,11,1,1,1,1
28.12.2014 Typ=12 Len=7: 120,114,12,28,1,1,1
There is no any 'format' here.
DISPLAYING and STORING are NOT the same when it comes to DATE.
When people say Oracle isn’t storing the date in the format they wanted, what is really happening is Oracle is not presenting the date in the character string format they expected or wanted.
When a data element of type DATE is selected, it must be converted from its internal, binary format, to a string of characters for human consumption. The conversion of data from one type to another is known as known a “conversion”, “type casting” or “coercion”. In Oracle the conversion between dates and character strings is controlled by the NLS_DATE_FORMAT model. The NLS_DATE_FORMAT can be set in any of several different locations, each with its own scope of influence.
I could go on with my leacture over DATE data type, but I am glad that someone has already got a good writeup over this. Please read this https://edstevensdba.wordpress.com/2011/04/07/nls_date_format/