How Can I Preserve Array Element Order When Joining Tables in PostgreSQL?

PostgreSQL Joins with Array Types: Ordering Array Elements

In PostgreSQL, it is often necessary to join tables with array type columns. However, when dealing with array types, maintaining the order of elements can be challenging.

Problem:

The goal is to retrieve data from the items table in the order of the elements in the array type column id_items from the some_chosen_data_in_order table.

Attempts:

Unsuccessful attempts include using the JOIN and subquery approaches, which fail to preserve the order of array elements.

Solution:

The solution involves using the unnest() function, which returns individual elements from an array. By using a LEFT JOIN with unnest() applied to id_items, we can get the items in the desired order.

Example:

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

This query will select items from the items table with ids: 1,2,3,2,3,5, in that order.

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