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https://issues.apache.org/jira/browse/CALCITE-759?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16499128#comment-16499128
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Julian Hyde commented on CALCITE-759:
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Thanks for doing this analysis. Very useful.
Of the ones that are supported by multiple databases (DATEPART, DAY, LAST_DAY,
TO_CHAR, TO_TIMESTAMP), are their specifications largely the same?
WEEKDAY (Mon=0, Sun=6) seems to occur in MySQL but not in ODBC or any other
database I could find. So we should use MySQL as the standard. Frankly, low
priority, because WEEKDAY\(x) == MOD(EXTRACT(DOW FROM x) + 1, 7).
If there is a conflict between ODBC and another database, the ODBC semantics
should only apply if they call using ODBC function syntax: {code}{fn
FUNCTION_NAME(arg, ...)}{code}
I think the high priority ones are the TO_xxx functions (e.g. TO_CHAR,
TO_TIMESTAMP). Anything that involves formatting or parsing is too complicated
to achieve using the existing functions.
What do other people think are the important functions to add to Calcite?
> Add DayOfWeek and other missing date/time functions
> ---------------------------------------------------
>
> Key: CALCITE-759
> URL: https://issues.apache.org/jira/browse/CALCITE-759
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
> Labels: dialect, newbie
>
> Calcite implements EXTRACT, FLOOR, CEIL, CAST, +, - on date/time values and
> much can be accomplished with these. But there are other useful functions in
> other databases.
> For example MySQL has DayOfWeek. See
> https://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html. It is
> tricky to achieve the same in Calcite (you'd need to subtract the epoch and
> take the interval modulo 7).
> We need to review the date/time functions in MySQL, Postgres and Oracle, and
> add functions to ensure that you can accomplish the same things in Calcite
> fairly easily.
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