Question

I have a MySQL InnoDB table laid out like so:
id (int), run_id (int), element_name (varchar), value (text), line_order, column_order

`MyDB`.`MyTable` (
  `id` bigint(20) NOT NULL,
  `run_id` int(11) NOT NULL,
  `element_name` varchar(255) NOT NULL,
  `value` text,
  `line_order` int(11) default NULL,
  `column_order` int(11) default NULL

It is used to store data generated by a Java program that used to output this in CSV format, hence the line_order and column_order.
Lets say I have 4 entries (according to the table description):

1,1,'ELEMENT 1','A',0,0
2,1,'ELEMENT 2','B',0,1
3,1,'ELEMENT 1','C',1,0
4,1,'ELEMENT 2','D',1,1

I want to pivot this data in a view for reporting so that it would look like more like the CSV would, where the output would look this:

---------------------
|ELEMENT 1|ELEMENT 2| <--- Element Name
---------------------
|   A     |   B     | <--- Value From line_order = 0
---------------------
|   C     |   D     | <--- Value From line_order = 1
---------------------

The data coming in is extremely dynamic; it can be in any order, can be any of over 900 different elements, and the value could be anything. The Run ID ties them all together, and the line and column order basically let me know where the user wants that data to come back in order. I want it to sort/group by line and column order in the displayed matrix.

Answer 1

You can do that with a self join:

select e1.element_name, e1.value, e2.value
from MyTable e1
inner join MyTable e2
on e1.element_name = e2.element_name
and e2.line_order = 1
where e1.line_order = 0

The from selects line_order = 1, the inner join selects line_order = 2.

Switch inner join to cross join if you’d like to return elements with only one line_order.

In reply to your comment, you could write out a fixed number of elements like:

select
    line_order
,   max(case when element_name = 'element 1' then value end) as Element1Value
,   max(case when element_name = 'element 2' then value end) as Element2Value
,   max(case when element_name = 'element 3' then value end) as Element3Value
,   ...
from MyTable
group by line_order

The max() construct assumes that (element_name, line_order) is unique.