How to Join PostgreSQL Tables with Array Types and Maintain Element Order?

Joining PostgreSQL Tables with Array Types and Preserving Element Order

Consider two tables in a database:

• items: Contains unique ID rows along with various fields.
• some_chosen_data_in_order: Includes an array type field named id_items with ID values from the items table arranged in a particular sequence.

To retrieve data from the items table based on the array field values in some_chosen_data_in_order while preserving their order, you can employ the following query:

SELECT t.*
FROM unnest(ARRAY[1,2,3,2,3,5]) item_id
LEFT JOIN items t on t.id=item_id

This query performs the following actions:

• unnest(ARRAY[1,2,3,2,3,5]): Unnests the provided array into individual elements, creating a sequence of rows.
• LEFT JOIN items t on t.id=item_id: Joins the unnested elements to the items table based on the id field.
• The LEFT JOIN ensures that all unnested elements are returned, even if they do not have matching rows in the items table.

By using this query, you can retrieve the items in the order specified by the id_items array in the some_chosen_data_in_order table.

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