How does following query work , could not find documents explaining how following query works.Are there any other similar queries for casting values?
SELECT date '2017-01-01' FROM dual;
Gives result 1/1/2017
Your query is using a date literal. From the Oracle documentation:
You can specify a DATE value as a string literal, or you can convert a character or numeric value to a date value with the TO_DATE function. DATE literals are the only case in which Oracle Database accepts a TO_DATE expression in place of a string literal.
To specify a DATE value as a literal, you must use the Gregorian calendar. You can specify an ANSI literal, as shown in this example:
DATE '1998-12-25'
Related
In my DB, there is a date field in the format yyyymmdd.
I have to get all the dates in the format dd-mm-yyyy for that particlar date.
ex:
Date
20170130
20170228
20170325
for the above dates, I need the output in the below format with the dates and day of the particular dates
date day
30-01-2017 tuesday
28-02-2017 tuesday
25-03-2017 saturday
If the column is a string, then it can hold invalid date values such as February 31, one way to avoid this is by a small function such as this:
create or replace
function my_to_date( p_str in varchar2 ) return date
is
begin
return to_date( p_str );
exception
when others then
return null;
end;
\\
select to_char(my_to_date('20170231'),'DD-MM-YYYY Day')
from dual
\\
Demo
Try below:
Select to_char(yrdate, 'dd-mm-yyyy'), to_char(yrdate, 'D') from yrtable
It sounds like your dates aren't actually DATE fields but some kind of CHAR field? The best option would be to convert to DATE and then convert back to CHAR:
SELECT TO_CHAR(TO_DATE(mydate, 'YYYYMMDD'), 'DD-MM-YYYY Day')
FROM mytable;
This uses the YYYYMMDD mask to convert your string into a date, then uses the mask DD-MM-YYYY Day to convert it back into a string. Use day if you want the day name in lowercase (as in your OP).
#user2778168 answer will give you the results you want. But why?
Your database does not have dates stored in yyyymmdd format or any other date format for at mater, unless it's defined with a character type definition. Oracle stores all dates in a single internal structure, and with only slight variations timestamps are the same. The format used only tells Oracle how to display the value or to convert a string to a date. Unless a specific format is specified Oracle uses the NLS_DATE_FORMAT for this determination. See here and scan down to "Datetime Format Models" for format specifications.
To see this run the following:
select value
from nls_session_parameters
where parameter = 'NLS_DATE_FORMAT';
Select yrdate default_format
, to_char(yrdate, 'dd-mm-yyyy') specified_format
, dump(yrdate) unformated
from yrtable;
alter session set nls_date_format = 'Month dd,yyyy';
Rerun the above queries.
It seems you hold date column(date1) in character format. Suppose you have a table named days:
SQL> desc days
date1 varchar2(10)
then,
we should convert it into date, and then into char format, with aliases in quotation marks to provide lowercase aliases as you wanted.
perhaps your database's date language is non-english like mine(turkish), then you need to convert it to english.
lastly, it'a appropriate to order the results according to converted date, seen from your output. So we can use the following SQL :
select to_char(to_date(date1,'yyyymmdd'),'dd-mm-yyyy') "date",
to_char(to_date(date1,'yyyymmdd'),'day','nls_date_language=english') "day"
from days
order by to_date(date1,'yyyymmdd');
D e m o
One of the columns my_column in my table is of type varchar where i store value of date in string. The format is 'MM/DD/YY'. I want to use cast function of hibernate to convert this column value to date. But it appears that the cast function accepts string of 'yy-mm-dd' format to convert. Is it possible to use cast for string with specific date format for conversion. Something like this: cast(am.my_column as date format 'mm/dd/yy')
cast function in hibernate is used this way: cast(am.my_column as date).
My use case is basically converting the column value from string to date and making a date comparison. cast(am.my_column as date format 'mm/dd/yy') > '12/30/2017'
Instead of casting a column value inside the query, you may consider to give '12/30/2017' as parameter (with type of Java Date). So that you can directly write am.my_column > :parameterDate
I have a question regarding SQL dates.
The table I am working with has a date field in the following format: "22-SEP-08". The field is a date column.
I am trying to figure out how to output records from 1/1/2000 to present day.
The code below is not filtering the date field:
Select distinct entity.lt_date
from feed.entitytable entity
where entity.lt_date >= '2000-01-01'
Any help regarding this issue is much appreciated. Thanks!
Edit: I am using Oracle SQL Developer to write my code.
DATEs do not have "a format". Any format you see is applied by the application displaying the date value.
You can either change the configuration of SQL Developer to display dates in a different format, or you can use to_char() to format the date the way you want.
The reason your statement does not work, is most probably because of the implicit data type conversion that you are relying on.
'2000-01-01' is a string value, not a date. And the string is converted using the NLS settings of your session. Given the fact that you see dates displayed as DD-MON-YY means that that is the format that is used by the evil implicit data type conversion. You should supply date values always as real date literals.
There are two ways of specifying a real date literal. The first is ANSI SQL and simple uses the keyword DATE in front of an ISO formatted string:
where entity.lt_date >= DATE '2000-01-01'
Note the DATE keyword in front of the string, wich makes it a real date literal not a string expression.
The other option is to use to_date() to convert a character value into a date:
where entity.lt_date >= to_date('2000-01-01', 'yyyy-mm-dd');
More details about specifying date literals can be found in the manual:
Date literals
to_date function
My guess is the data type isn't a Date. Just in case its a char type, try to convert it using the Oracle TO_DATE() function. The Oracle documentation below should help you with parameters.
http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions183.htm
An implicit datatype conversion bites once again.
You're right. The predicate is not doing the comparison you are expecting,
Oracle is performing an implicit datatype conversion, from DATE to VARCHAR, so that it can do a comparison to the string literal.
If lt_date column is DATE datatype, then Oracle is seeing your where clause:
where entity.lt_date >= '2000-01-01'
Oracle is actually seeing it as if it's written like this:
where TO_CHAR(entity.lt_date) >= '2000-01-01'
And that's where the "format" problem comes in. The column itself does not have a "format". Because the second argument to the TO_CHAR function is not supplied, Oracle is using the value of the NLS_DATE_FORMAT parameter (from your session). And that's probably set to DD-MON-YY. Which is why that's the "format" you're seeing when you a run a SELECT statement in SQL*Plus. Because the DATE value is (again) being run through a TO_CHAR function to get a string that can be displayed.
To get the "filtering" you want, don't do a comparison to a string literal. Instead, do the comparison to an expression that has DATE datatype.
You can use the Oracle TO_DATE function. And you don't want to rely on setting of NLS_DATE_FORMAT, explicitly specify the format model as the second argument to the function. For example:
DO THIS
where entity.lt_date >= TO_DATE('2000-01-01','YYYY-MM-DD')
DON'T DO THIS
It's also possible to specify the format model as the second argument to the TO_CHAR function.
where TO_CHAR(entity.lt_date,'YYYY-MM-DD') >= '2001-01-01'
But you don't want to do that because that's going to force Oracle to evaluate that expression on the left side for every flipping row in the table, so it has a string value to do the comparison. (That's true unless someone created a function-based index for you.) If you do the comparison on the bare column, using the TO_DATE on the literal side, Oracle can make effective use of an appropriate index (with lt_date as the leading column) to satisfy the predicate.
The date column that I have is in varchar2 and I want to convert those values in YYYY-MM-DD
DATE
7/26/2013
7/29/2013
8/1/2013
8/4/2013
7/28/2013
7/31/2013
8/3/2013
7/30/2013
8/5/2013
7/25/2013
8/2/2013
8/6/2013
7/27/2013
You should never store dates in a VARCHAR column
So in order to display it differently now, you need to first convert the string to a date and then back to a string
If you are certain that all "dates" do have the right (and same) format, then the following should work:
select to_char(to_date(date, 'mm/dd/yyyy'), 'yyyy-mm-dd')
from the_table;
But I wouldn't be surprised if that gives you an error because one or more rows have a date which is formatted differently. Something which could not have happened had you defined the column to be of type DATE right from the beginning.
You should really, really consider changing that column to be a real DATE column.
Btw: DATE is a horrible name for such a column. It is a reserved word and it simply doesn't tell you anything about what is actually stored in that column (a "start date", an "end date", a "birth date", a "due date", ...)
You have to convert your string to date and than convert to char with expected format
select TO_CHAR(TO_DATE(datecol, 'MM/DD/YYYY'),'YYYY-MM-DD')
from your_table
Sql Fiddle Demo
you can use REGEXP_REPLACE function to manipulate strings or to_date and to_char to convert string to date and than to string back with different format.
select to_char(TO_DATE("Date", 'MM/DD/YYYY'),'yyyy-mm-dd')
from Table1
SQL FIDDLE
I'm sure this is quite simple, but I've been stuck on it for some time. How can I convert a varchar field (YYYYMM) to a date (MM/01/YY) in SQL?
Thanks.
Edit: I'm using Open Office Base (HSQL), not MySQL; sorry for the confusion.
Try the str_to_date and date_format functions. Something like:
select date_format( str_to_date( my_column, '%Y%c' ), '%c/01/%y' ) from my_table
try :
SELECT STR_TO_DATE(CONCAT(myDate,'01'),'%Y%m%d')
FROM myTable
Use STR_TO_DATE:
From mysql.com:
STR_TO_DATE(str,format)
This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts.
The date, time, or datetime values contained in str should be given in the format indicated by format. For the specifiers that can be used in format, see the DATE_FORMAT() function description. If str contains an illegal date, time, or datetime value, STR_TO_DATE() returns NULL. Starting from MySQL 5.0.3, an illegal value also produces a warning.
Range checking on the parts of date values is as described in Section 11.3.1, “The DATETIME, DATE, and TIMESTAMP Types”. This means, for example, that “zero” dates or dates with part values of 0 are allowed unless the SQL mode is set to disallow such values.
mysql> SELECT STR_TO_DATE('00/00/0000', '%m/%d/%Y');
-> '0000-00-00'
mysql> SELECT STR_TO_DATE('04/31/2004', '%m/%d/%Y');
-> '2004-04-31'
Get the year:
SUBSTRING(field FROM 2 FOR 2)
Get the month:
SUBSTRING(field FROM -2 FOR 2)
Compose the date:
CONCAT(SUBSTRING(field FROM -2 FOR 2), '/01/', SUBSTRING(field FROM 2 FOR 2))
This will convert from YYYYMM to MM/01/YY.
To be clear: if you're looking for method to convert some value of type Varchar/Text to value of type Date than solutions are:
using CAST function
CAST(LEFT('201205',4)||'-'||SUBSTRING('201205' FROM 5 FOR 6)||'-01' AS DATE)
starting from OpenOffice 3.4 (HSQLDB 2.x) new Oracle-like function TO_DATE supposed to be available
TO_DATE('201205','YYYYMM')
in addition to the written i can mention that you also can construct a string with ANSI/ISO 'YYYY-MM-DD' formatted representation of the date,- Base will acknowledge that and succesfully convert it to the Date type if necessary (e.g. INSERTing in Date typed column etc.)
Here is doc's on HyperSQL and highly recommended OO Base guide by Andrew Pitonyak