Crossing/Rotating table rows to rows and columns

From: Iuri Sampaio <iuri(dot)sampaio(at)gmail(dot)com>
To: pgsql-sql <pgsql-sql(at)lists(dot)postgresql(dot)org>
Subject: Crossing/Rotating table rows to rows and columns
Date: 2020-09-03 02:58:46
Message-ID: 2B732C2C-5DC9-4D66-A54C-90EFF8780541@gmail.com
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Hi there,
How would I convert/rotate (i.e. cross table) the following datasource, which is originally returned by rows (i.e. datetime and total), to rows as hours and columns as dates, where the columns (dates) will be assigned with "total" as their value.
Here it is the chunk of code to convert from base64url to binary PNG

select date_trunc('hour', o.creation_date) AS datetime,
COUNT(1) AS total
FROM cr_items ci, acs_objects o, cr_revisions cr
WHERE ci.item_id = o.object_id
AND ci.item_id = cr.item_id
AND ci.latest_revision = cr.revision_id
AND ci.content_type = :content_type
AND o.creation_date BETWEEN :creation_date::date - INTERVAL '6 day' AND :creation_date::date + INTERVAL '1 day'
GROUP BY 1 ORDER BY datetime ASC''

From the table structure, such as:

hour | total
------------------------+-------
2020-07-26 02:00:00+00 | 1
2020-07-26 04:00:00+00 | 7
2020-07-26 05:00:00+00 | 6
2020-07-26 06:00:00+00 | 6
2020-07-26 07:00:00+00 | 17
2020-07-26 08:00:00+00 | 17
2020-07-26 09:00:00+00 | 6
2020-07-26 10:00:00+00 | 8
2020-07-26 11:00:00+00 | 14
2020-07-26 12:00:00+00 | 16
2020-07-26 13:00:00+00 | 10
2020-07-26 14:00:00+00 | 17
2020-07-26 15:00:00+00 | 15
2020-07-26 16:00:00+00 | 2
2020-07-27 00:00:00+00 | 1
2020-07-27 06:00:00+00 | 1
..
2020-08-01 07:00:00+00 | 7
2020-08-01 08:00:00+00 | 4
2020-08-01 09:00:00+00 | 7
2020-08-01 10:00:00+00 | 10
2020-08-01 11:00:00+00 | 20
2020-08-01 12:00:00+00 | 25
2020-08-01 13:00:00+00 | 18
2020-08-01 14:00:00+00 | 14
2020-08-01 15:00:00+00 | 12
2020-08-01 16:00:00+00 | 4
(91 rows)

It would result in the table, as in:

hour 2020-7-26 2020-7-27 ... 2020-7-31 2020-8-01
0:00:00
1:00:00
2:00:00
3:00:00
4:00:00
5:00:00 1
6:00:00 2 2 4 22 7 4
7:00:00 8 2 3 8 1
8:00:00 3 8 4 1 9 4
9:00:00 4 6 2 35 8
10:00:00 9 19 14 2 10 2
11:00:00 11 8 7 13 10 13 10
12:00:00 12 7 18 12 8 12 5
13:00:00 6 14 8 24 10 6 6
14:00:00 8 10 9 7 14 11 4
15:00:00 21 10 4 2 13 15
16:00:00 12 15 11 10 22 22
17:00:00 30 14 11 28 10 29
18:00:00 1
19:00:00
20:00:00
21:00:00
22:00:00
23:00:00

I've tried to use crosstabN(text sql), to solve the problem directly in the datasource layer, but apparently tablefunc is not supported in the datamodel Squema https://www.postgresql.org/docs/9.2/tablefunc.html <https://www.postgresql.org/docs/9.2/tablefunc.html>
ERROR: function crosstab(unknown, unknown) does not exist
LINE 1: select * from crosstab('select o.creation_date::date AS day ...
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.

Thus, I was wondering if there is a better approach to write a beautiful code out of it.

Does anyone have an idea on how to write this crosstable display?

Best wishes,
I

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