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https://issues.apache.org/jira/browse/TAJO-746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13972388#comment-13972388
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Keuntae Park commented on TAJO-746:
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OK, [~hyunsik].
I created a bug fix issue TAJO-770 and uploaded the patch.
> Implements function COALESCE
> ----------------------------
>
> Key: TAJO-746
> URL: https://issues.apache.org/jira/browse/TAJO-746
> Project: Tajo
> Issue Type: New Feature
> Reporter: hyoungjunkim
> Assignee: hyoungjunkim
> Attachments: TAJO-746.patch, TAJO-746_2.patch
>
>
> See title.
> The next description is from the postgresql
> document(http://www.postgresql.org/docs/9.1/static/functions-conditional.html).
>
> {noformat}
> COALESCE(value [, ...])
> {noformat}
> The COALESCE function returns the first of its arguments that is not null.
> Null is returned only if all arguments are null. It is often used to
> substitute a default value for null values when data is retrieved for
> display, for example:
> {code:sql}
> SELECT COALESCE(description, short_description, '(none)') ...
> {code}
> Like a CASE expression, COALESCE only evaluates the arguments that are needed
> to determine the result; that is, arguments to the right of the first
> non-null argument are not evaluated. This SQL-standard function provides
> capabilities similar to NVL and IFNULL, which are used in some other database
> systems.
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