I've got a column to import into an Azure SQL DB that is supposed to be made of dates only but of course contains errors.
In TSQL I would like to do something like: convert to date if it's possible otherwise null.
Does anyone know a statement to test the convertibility of a string into a date?
use TryCast or Isdate
select
try_Cast('test' as date)
select try_Cast('4' as date)
select case when ISDATE('test')=1 then cast('test' as date) else null end
TryCast will fail if the expression is not in expected format ..ie.,if the explicit conversion of expression is not permitted
select
try_cast( 4 as xml)
select try_Cast(4 as date)
You could use TRY_PARSE:
Returns the result of an expression, translated to the requested data type, or null if the cast fails. Use TRY_PARSE only for converting from string to date/time and number types.
SELECT TRY_PARSE('20129901' AS DATE)
-- NULL
Additionaly you could add culture:
SELECT TRY_PARSE('10/25/2015' AS DATE USING 'en-US')
And importing:
INSERT INTO target_table(date_column, ...)
SELECT TRY_PARSE(date_string_column AS DATE) ...
FROM source_table
...
Related
In this query the 'Daily' in the case will be replaced by a variable. I am not able to make this query work. I want to have the date column being either a day, a week a month or a year based on the value of the variable. but it is giving me various errors..
CASE types date and double precison cannot be matched
syntax error near "as"
what am I doing wrong?
select
case 'Daily'
when 'Daily' then DATE(to_timestamp(e.startts)) as "Date",
when 'Weekly' then DATE_PART('week',to_timestamp(e.startts)) as "Date",
when 'Monthly' then to_char(to_timestamp(e.startts), 'mm/yyyy') as "Date",
when 'Yearly' then to_char(to_timestamp(e.startts), 'yyyy') as "Date",
end
sum(e.checked)
from entries e
WHERE
e.startts >= date_part('epoch', '2020-10-01T15:01:50.859Z'::timestamp)::int8
and e.stopts < date_part('epoch', '2021-11-08T15:01:50.859Z'::timestamp)::int8
group by "Date"
CASE ... END is an expression. An expression must have a well-defined data type, so PostgreSQL makes sure that the expressions in the THEN clause have the same data type (or at least compatible ones).
You would need a type cast, probably to text, in the first two branches:
... THEN CAST (date(to_timestamp(e.startts)) AS text)
But it would be much better to use to_char in all branches – there are format codes for everything you need.
An expression can have no alias, only an entry in the SELECT or FROM list can. So you need to append AS "Date" at the end of the CASE ... END expression, not somewhere in the middle.
My task is to convert a ABAP style date (i.e. 2017-11-20 which is represented as string "20171120") to a HANA date via sql script. This can easily be done by:
select to_date('20171120','YYYYMMDD') from dummy;
But there is another requirement: if the abap date is initial (value '00000000') the database shall store a null value. I have found a working solution: I replace the potential initial date '00000000' with 'Z' and trim the string to null if only 'Z' is found:
select to_date(trim(leading 'Z' from replace('00000000','00000000','Z')),'YYYYMMDD') from dummy;
-- result: null
select to_date(trim(leading 'Z' from replace('20171120','00000000','Z')),'YYYYMMDD') from dummy;
-- result: 2017-11-20
But this looks like a dirty hack. Has anybody an idea for a more elegant solution?
As explained in my presentation Innovation with SAP HANA - What are my options all that string manipulation is really not necessary.
Instead, use the appropriate conversion functions when dealing with ABAP date and time data. In this case, DATS_TO_DATE is the correct function.
with in_dates as
( select '20171120' as in_date from dummy
union all select '00000000' as in_date from dummy)
select
dats_to_date(in_date)
, in_date
from in_dates;
|DATS_TO_DATE(IN_DATE) |IN_DATE
-------------------------+---------
|2017-11-20 |20171120
|? |00000000
The ? here is the output representation for NULL.
DATS_TO_DATE does not return NULL if the given date is initial (0000-00-00), but a special date value (-1-12-31 to be precise).
To receive a NULL value in this case, as you requested, use the following statement:
NULLIF( DATS_TO_DATE(?), DATS_TO_DATE('00000000'))
e. g.:
INSERT INTO null_test VALUES (NULLIF( DATS_TO_DATE('00000000'), DATS_TO_DATE('00000000')));
=> returns NULL
INSERT INTO null_test VALUES (NULLIF( DATS_TO_DATE('20171224'), DATS_TO_DATE('00000000')));
=> returns 2017-12-24
As there are no tedious string operations involved, this statement should yield good performance.
select complaintno from complaintprocess where endtime='';
It Is Not Working
In complaintprocess table endtime datatype is timestamp without time zone.
Here I want to get one of the column in complaintprocess where endtime is empty.
You could not store '' as timestamp. I suspect that by blank you mean NULL value.
SELECT CAST('' AS timestamp);
-- ERROR: invalid input syntax for type timestamp: ""
To filter them you could use:
SELECT complaintno
FROM complaintprocess
WHERE endtime IS NULL;
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';
In my SQL Server database I have the dates stored as char(12) in the following format:
yyyymmddhhmm
I didn't create the definition and I cannot modify it. I always dealt with this string at application level, by using C#.
Now I need to perform a task in TSQL and I need to group by month. Therefore I need to extract the month. Is there any TSQL function available for this task?
In case there is not, is it a good solution to create a stored procedure, getMonth(stringDate) that takes the string and extract the 4th and 5th characters from it? Can I use the clause:
group by getMonth(stringDate)
in my query? Thanks
You can;
SUBSTRING(fld, 5, 2)
Personally I would not create a UDF for something so simple (which is what you would consider rather than an SP) unless you find yourself needing to cast that string to DATETIMEs
You can use the following to get your month, since month is always 2 characters after the 4 character year.
declare #date char(12)
set #date = '201203220906'
select substring(#date, 5, 2)
results: 03
or another way to get it is, then you can group by the results in either query:
declare #date char(12)
set #date = '201203220906'
select Month(cast(left(#date, 8) as datetime))
Assuming
CREATE TABLE #Table(
DateValue char(12),
Value int)
INSERT INTO #Table VALUES ('20120110833', 1)
INSERT INTO #Table VALUES ('20120110833', 2)
INSERT INTO #Table VALUES ('20120110833', 3)
INSERT INTO #Table VALUES ('20120210833', 4)
INSERT INTO #Table VALUES ('20120210833', 5)
You can simply do this:
select
MONTH(CAST(LEFT(DateValue, 8) as datetime)) Month,
SUM(value)
FROM
#Table
GROUP BY
MONTH(CAST(LEFT(DateValue, 8) as datetime))
trim the hour/minute part, cast as datetime and apply MONTH function
For this specific case (date in char type with format yyyymmddhhmm), you can use in your query the next functions:
substring (to extract yyyymmdd),
convert (to get datetime value),
datepart (to get month component)
...then you can group by month (or whatever date component), change datecolumnname and tablename with appropiate values
select datepart(month,convert(datetime,substring(datecolumnname,1,8),112)),
count(datepart(month,convert(datetime,substring(datecolumnname,1,8),112)))
from tablename
group by datepart(month,convert(datetime,substring(datecolumnname,1,8),112))