On 2018-09-16 1:29 AM, John Found wrote:
Is there some relation between the indexes used in the query, the GROUP BY
fields used
and the order of the result rows, when no "ORDER BY" clause is used?
I am asking, because I noticed, that on some queries, when I am using "ORDER
BY" the query always
use temporary b-tree for ordering, but by including the needed fields in the "GROUP
BY" clause
and removing the ORDER BY clause, the query returns the rows in the proper
order without temp b-tree.
So, is it safe to use this implicit ordering, or this behavior can be changed
in the future versions of SQLite?
The answer to your question, is no, never. Using ORDER BY is the *only* safe
way to guarantee results come in a particular order. When you don't use ORDER
BY you are explicitly saying that the order of result rows isn't significant and
so the DBMS can use whatever order it feels like at any time without any prior
notice of changes. -- Darren Duncan
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