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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4401) Document USING clause in joins
Date Fri, 09 Oct 2009 13:06:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12764006#action_12764006
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Knut Anders Hatlen commented on DERBY-4401:
-------------------------------------------

Some examples with toursdb:

-- Inner join that shows the number of cities in each country
SELECT COUNTRY, COUNT(*) AS NUM
    FROM COUNTRIES INNER JOIN CITIES USING (COUNTRY)
    GROUP BY COUNTRY ORDER BY NUM

-- Left outer join that shows the same as the previous join, but also includes countries with
no cities in the result
SELECT COUNTRY, COUNT(CITY_ID) AS NUM
    FROM COUNTRIES LEFT OUTER JOIN CITIES USING (COUNTRY)
    GROUP BY COUNTRY ORDER BY NUM

> Document USING clause in joins
> ------------------------------
>
>                 Key: DERBY-4401
>                 URL: https://issues.apache.org/jira/browse/DERBY-4401
>             Project: Derby
>          Issue Type: Improvement
>          Components: Documentation
>    Affects Versions: 10.6.0.0
>            Reporter: Knut Anders Hatlen
>            Priority: Minor
>
> DERBY-4370 made some of the join operations accept a USING clause. This should be documented
in the reference manual.
> The JOIN operations section talks about "join clause", which should be fine since that
could mean both ON clause and USING clause.
> The sections INNER JOIN operation, LEFT OUTER JOIN operation and RIGHT OUTER JOIN operation
need to be updated with the new syntax. We need to replace
> {
>     ON booleanExpression
> }
> with
> {
>     { ON booleanExpression } |
>     { USING ( Simple-column-Name [ , Simple-column-Name ]* ) }
> }
> Perhaps it would make sense to factor out this part of the syntax into a separate element
JoinSpecification, and explain the meaning of USING there.

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