[jira] [Updated] (TAJO-746) Implements function COALESCE

["hyoungjunkim (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TAJO-746?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

hyoungjunkim updated TAJO-746:
------------------------------

    Attachment: TAJO-746.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
>
>
> 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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