Create unpivot-multiple-columns in-snowflake.md

Author: structured-query-language

unpivot-multiple-columns in-snowflake.md

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+# Unpivot multiple columns in Snowflake
+
+Suppose you have a Wide Table format Performance Ratings data as following:
+
+| NAME         | ACTING_RATING | ACTING_COMMENTS | COMEDY_RATING | COMEDY_COMMENTS | MUSICAL_PERFORMANCE_RATING | MUSICAL_PERFORMANCE_COMMENTS |
+|--------------|---------------|-----------------|---------------|-----------------|----------------------------|------------------------------|
+| Groucho Marx | 4             | Awesome         | 3             | Super           | 4                          | Really good                  |
+| Harpo Marx   | 4             | Awesome         | 4             | Awesome         | 4                          |                              |
+| Groucho Marx | 4             |                 | 3             | Thumbs up       | 4                          | Nice                         |
+| Harpo Marx   | 4             | Best Acting     | 4             | Nice            | 4                          | Best performance Award!      |
+
+and you need to convert it to a Long Table Format as following
+
+| NAM          | SKILL                      | SKILL_RATING | COMMENTS                | SKILL_COMMENTS               | SPLIT(SKILL, '-')[1] |
+|--------------|----------------------------|--------------|-------------------------|------------------------------|----------------------|
+| Groucho Marx | ACTING_RATING              | 4            | Awesome                 | ACTING_COMMENTS              |                      |
+| Groucho Marx | COMEDY_RATING              | 3            | Super                   | COMEDY_COMMENTS              |                      |
+| Groucho Marx | MUSICAL_PERFORMANCE_RATING | 4            | Really good             | MUSICAL_PERFORMANCE_COMMENTS |                      |
+| Harpo Marx   | ACTING_RATING              | 4            | Awesome                 | ACTING_COMMENTS              |                      |
+| Harpo Marx   | COMEDY_RATING              | 4            | Awesome                 | COMEDY_COMMENTS              |                      |
+| Harpo Marx   | MUSICAL_PERFORMANCE_RATING | 4            |                         | MUSICAL_PERFORMANCE_COMMENTS |                      |
+| Groucho Marx | ACTING_RATING              | 4            |                         | ACTING_COMMENTS              |                      |
+| Groucho Marx | COMEDY_RATING              | 3            | Thumbs up               | COMEDY_COMMENTS              |                      |
+| Groucho Marx | MUSICAL_PERFORMANCE_RATING | 4            | Nice                    | MUSICAL_PERFORMANCE_COMMENTS |                      |
+| Harpo Marx   | ACTING_RATING              | 4            | Best Acting             | ACTING_COMMENTS              |                      |
+| Harpo Marx   | COMEDY_RATING              | 4            | Nice                    | COMEDY_COMMENTS              |                      |
+| Harpo Marx   | MUSICAL_PERFORMANCE_RATING | 4            | Best performance Award! | MUSICAL_PERFORMANCE_COMMENTS |                      |
+
+This can be achieve by using the UNPIVOT function or the UNION ALL in Snowflake
+
+## Using UNPIVOT
+
+```sql
+select 
+  name
+  , skill
+  , skill_rating
+  , comments
+  , skill_comments
+from performer_ratings
+    unpivot include nulls (skill_rating for skill in (acting_rating,  comedy_rating, musical_performance_rating)) 
+    unpivot include nulls (comments for skill_comments in (acting_comments,comedy_comments, musical_performance_comments)) 
+--Following where clause is added to filter the unmatched rows
+where split(skill, '_')[0] = split(skill_comments, '_')[0];
+
+```
+
+
+## Using UNION ALL
+
+```sql
+
+select NAME
+  , 'ACTING_RATING' as SKILL, ACTING_RATING as SKILL_RATING, ACTING_COMMENTS as SKILL_COMMENTS
+from performer_ratings
+union all
+select NAME
+  , 'COMEDY_RATING', COMEDY_RATING, COMEDY_COMMENTS
+from performer_ratings
+union all
+select NAME
+  , 'MUSICAL_PERFORMANCE_RATING', MUSICAL_PERFORMANCE_RATING, MUSICAL_PERFORMANCE_COMMENTS
+from performer_ratings
+;
+```