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From "Sean Hsuan-Yi Chu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-2354) Documentation for Concat Function & Concat Operator
Date Mon, 02 Mar 2015 17:38:05 GMT
Sean Hsuan-Yi Chu created DRILL-2354:
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             Summary: Documentation for Concat Function & Concat Operator 
                 Key: DRILL-2354
                 URL: https://issues.apache.org/jira/browse/DRILL-2354
             Project: Apache Drill
          Issue Type: Improvement
          Components: Documentation
            Reporter: Sean Hsuan-Yi Chu
            Assignee: Bridget Bevens


In Drill, we have two ways to concatenate Strings:
1. Concat Function: concat(c1, c2, c3, ...)
2. Concat Operator: c1 || c2 || c3 || ...

They are doing same thing except for dealing with NULL:
1. For concat function, NULL is treated as empty string

2. For concat operator: if any input is NULL, output NULL (no matter what other columns are)

These are subtle difference and would be better to be documented.
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Some discussion can be found from DRILL-2328



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