Add GROUP_CONCAT aggregate function to views

GROUP_CONCAT is not part of the SQL ANSI standard so it will limit portability of the feature.

This should be dealt with in contrib.

IIRC there is already an issue for this.

The patch fails for me (for 8.4.x). I think it's missing ']' character.

Also I'd like to point out that group_concat is used for other fields than just numeric. Changing 'field' => 'numeric' to 'field' => 'field' enables concatenation of textual fields as well.

There are already some issues (like the one I linked as related) but no real fixes. Some recommend using the contrib module Views Aggregator Plus but does not solve the problem for me. It introduces a whole new paradigm for views which has it's own problems.

Here is my crude patch of how I got the group concat to work.

The patch does not apply using patch level p2. Here is an updated one that does.

The change might be crude, not portable and lacking features such as the ability to define separators and the like, but for a simple case it has worked well for me.

Patch in #10 does not apply either. This should work.

Here is the patch from #11 rerolled for Drupal 8.6.1.

It works. thanks

New features go into the latest dev branch. Also unassigned after 18 months.

The field argument for the handler shall not be "field" as it tries to load it from the entity object. I am having problem when trying to actually output it.
Here is an updated patch.

This needs tests.

tested #15 patch and found

• that it would prevent saving views actually using group_concat (on strings)
• hence added a GroupByString to views and
• added Group Concat DISTINCT option

Wouldn’t the addition of GROUP_CONCAT to Core limit it’s installation on non MySQL databases?

Patch #17 is working well for me. I would however love to see some more settings on this Filter Plugin - specifically to allow the substitution of a separator (e.g. not a comma) also there is no space between records. Allowing a unique separator would fix that. I'm wondering why this does not allow the use of token/twig replacements. Maybe that's too much to task.

Patch in #17 works great for me - thanks!

#17 works for me too, but it only returns ID values. The formatting options are removed from the field.

This would be great to add as well as what #20 suggested.

This works with data export which is a bonus as its needed for xml feeds for commerce.

Correction. The ID value only returned on commerce variation attributes. With the correct relationship fields it works correctly.

Patch has solved our problems too. thank you. we used "rewrite" and {{ |replace({',': "
"})|raw}} to get each value on to its own line. assuming same could be done if someone wanted to replace 'comma' with 'comma space'

@petednz: We need to add testing for the added functionality. First to test if the added functionality does what it is supposed to and second to make sure that it keep working and that some future update does not break the added functionality.

Here's patch #17 that fixes the PHP 7.4 deprecation notice and some linting errors.

Fixed PHPCss error.

The original patch was missing some code. I've added it back and included the changes in #29.

The above patch wasn't applying to core version 9.2.2 and above.
Its minor change which removes the space from the comment line // https://www.drupal.org/node/571548. to make it compatible with latest version.

The latest patch doesn't work for postgresql

Just testing locally this works:

public function aggregationMethodConcatSimple($group_type, $field) {
    return strtoupper($group_type) . '(' . $field . ', \',\')';
  }

It needs to specify the string to use as glue, ie ','

Moving back to needs work based on comment #36 and no test cases being added

Can we have a list of entity links instead of list of strings? It would be very useful too.