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Using GROUP_CONCAT to Combine Rows in a Drupal Query
Recently I was working on a D7 to D8 migration. I was trying to import news items and their taxonomy terms (among many other things). To make things simple I wanted the query results to have (for each node) a single field that contained a comma-separated list of taxonomy terms which I could then explode during the row processing. Using GROUP_CONCAT we can achieve this! Let’s break it down:
The Drupal 7 site has the following structure (focusing on the important bits for this blog post):
123-- News Item (news_item) <content type>---- Categories (field_categories) <field collection>------ Audience (field_term_audience) <taxonomy reference; unlimited values>The migration relies on the d7_node migrate source plugin, which basically queries for nodes of a specific type. The query object looks like this (simplified for this blog post):
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Drupal 7 – Commerce Migration Class
Here’s a migration class I’ve been working on to import 8200 products. The biggest feature of this code is that it will automatically create a single product display node that groups all products who share the same “grouping identifier.” So, in my CSV import file I have a “grouping_identifier” column. If a product is available in ten colors, and they all share the same grouping identifier, a single product display will be created and each of these products will be referenced in it. This will result in a product on the frontend that allows ten different color choices. I don’t have the time right now to explain anything more… please leave a comment if you have a question.
