MaxGekk commented on a change in pull request #28558:
URL: https://github.com/apache/spark/pull/28558#discussion_r426370104
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File path: docs/sql-ref-datetime-pattern.md
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@@ -76,6 +76,57 @@ The count of pattern letters determines the format.
- Year: The count of letters determines the minimum field width below which
padding is used. If the count of letters is two, then a reduced two digit form
is used. For printing, this outputs the rightmost two digits. For parsing, this
will parse using the base value of 2000, resulting in a year within the range
2000 to 2099 inclusive. If the count of letters is less than four (but not
two), then the sign is only output for negative years. Otherwise, the sign is
output if the pad width is exceeded when 'G' is not present.
+- Month: If the number of pattern letters is 3 or more, the month is
interpreted as text; otherwise, it is interpreted as a number. The text form is
depend on letters - 'M' denotes the 'standard' form, and 'L' is for
'stand-alone' form. The difference between the 'standard' and 'stand-alone'
forms is trickier to describe as there is no difference in English. However, in
other languages there is a difference in the word used when the text is used
alone, as opposed to in a complete date. For example, the word used for a month
when used alone in a date picker is different to the word used for month in
association with a day and year in a date. Here are examples for all supported
pattern letters:
+ - `'M'` or `'L'`: Month number in a year starting from 1. There is no
difference between 'M' and 'L'. Month from 1 to 9 are printed without padding.
+ ```sql
+ spark-sql> select date_format(date '1970-01-01', "M");
+ 1
+ spark-sql> select date_format(date '1970-12-01', "L");
+ 12
+ ```
+ - `'MM'` or `'LL'`: Month number in a year starting from 1. Zero padding is
added for month 1-9.
+ ```sql
+ spark-sql> select date_format(date '1970-1-01', "LL");
+ 01
+ spark-sql> select date_format(date '1970-09-01', "MM");
+ 09
+ ```
+ - `'MMM'`: Short textual representation in the standard form. The month
pattern should be a part of a date pattern not just a stand-alone month except
locales where there is no difference between stand and stand-alone forms like
in English.
+ ```sql
+ spark-sql> select date_format(date '1970-01-01', "d MMM");
+ 1 Jan
+ spark-sql> select to_csv(named_struct('date', date '1970-01-01'),
map('dateFormat', 'dd MMM', 'locale', 'RU'));
+ 01 янв.
+ ```
+ - `'LLL'`: Short textual representation in the stand-alone form. It should
be used to format/parse only months without any other date fields.
+ ```sql
+ spark-sql> select date_format(date '1970-01-01', "LLL");
+ Jan
+ spark-sql> select to_csv(named_struct('date', date '1970-01-01'),
map('dateFormat', 'LLL', 'locale', 'RU'));
+ янв.
+ ```
+ - `'MMMM'`: full textual month representation in the standard form. It is
used for parsing/formatting months as a part of dates/timestamps.
+ ```sql
+ spark-sql> select date_format(date '1970-01-01', "MMMM yyyy");
+ January 1970
+ spark-sql> select to_csv(named_struct('date', date '1970-01-01'),
map('dateFormat', 'd MMMM', 'locale', 'RU'));
+ 1 января
+ ```
+ - `'LLLL'`: full textual month representation in the stand-alone form. The
pattern can be used to format/parse only months.
+ ```sql
+ spark-sql> select date_format(date '1970-01-01', "LLLL");
+ January
+ spark-sql> select to_csv(named_struct('date', date '1970-01-01'),
map('dateFormat', 'LLLL', 'locale', 'RU'));
+ январь
+ ```
+ - `'LLLLL'` or `'MMMMM'`: Narrow textual representation of standard or
stand-alone forms. Typically it is a single letter.
Review comment:
I wrote above that the list of all supported patterns or do you think we
must say for idiots that others are not supported?
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