How to transpose multiple rows into multiple columns?

Question

Grouping col_1 in ascending values of seq column to display values from comment columns in multiple columns for below sample data:

col_1  |  Seq  |  Comment |
--------------------------|
ABC    |   30  |  TestC   |
ABC    |   50  |  TestE   |
ABC    |   80  |  TestG   |
ABC    |   10  |  TestA   |
ABC    |   60  |  TestF   |
ABC    |   20  |  TestB   |
ABC    |   70  |  TestF   |
ABC    |   40  |  TestD   |
DEF    |   20  |  TestB   |
DEF    |   10  |  TestA   |
GHI    |   10  |  TestA   |
--------------------------|

Expected output of sql should be:
Col_1  | Col_2 | Col_3 | Col_4 | Col_5 | Col_6 | Col_7 | Col_8 | 
-------|-------|-------|-------|-------|-------|-------|-------|
ABC    | TestA | TestB | TestC | TestD | TestE | TestF | TestG |
DEF    | TestA | TestB |       |       |       |       |       |
GHI    | TestA |       |       |       |       |       |       |
-------|-------|-------|-------|-------|-------|-------|-------|

Gordon Linoff · Accepted Answer · 2018-07-22 21:18:29Z

1

You can use conditional aggregation and row_number():

select col_1,
       max(case when seqnum = 1 then comment end) as col_2,
       max(case when seqnum = 2 then comment end) as col_3,
       max(case when seqnum = 3 then comment end) as col_4,
       . . .
from (select t.*,
             row_number() over (partition by col_1 order by seq) as seqnum
      from t
     ) t
group by col_1;

answered Jul 22, 2018 at 21:18

Gordon Linoff

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2 Comments

Rinku Gautam Over a year ago

By using CASE or DECODE, it unnecessarily uses huge lines of code. I want to avoid hard-code kind of coding and use advanced features of SQL. Even a procedure will help.

Gordon Linoff Over a year ago

@RinkuGautam . . . This answers the question that you asked. If you have another question, you should ask it as a question.

Kaushik Nayak · Accepted Answer · 2018-07-23 04:13:42Z

0

This basically uses the same row_number function used in Gordon's answer, but for a PIVOT clause.

SELECT *
FROM (
    SELECT t.COL_1
        ,t.comments
        ,row_number() OVER (
            PARTITION BY col_1 ORDER BY seq
            ) AS seqnum
    FROM t
    ) t
PIVOT(MAX(comments) FOR seqnum IN (1 as col_2,2 as col_3,3 as col_4,
                                   4 as col_5,5 as col_6,6 as col_7,
                                   8 as col_8));

Demo

answered Jul 23, 2018 at 4:13

Kaushik Nayak

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