When a SQL DELETE query times out, what happens with the data?

Question

If I were to run a DELETE FROM some_table, and that were to timeout, what happens to the data?

The way I see it, one of two things might happen:

• The data is deleted up to the point where the query times out, so if there were 1,000,000 entries in the database and the first 500,000 were deleted, they'd stay deleted. The database now contains half as many as it did before the query was run.

• The data is deleted, the query times out, the data is rolled back (I would guess from the logs made by DELETE?). The database now contains the exact same data it started with.

Both seem logical. Would one happen 100% of the time? Or is this dependent on some settings I'm unaware of? Note that I'm not asking about the viability of the DELETE, I realize that TRUNCATE would likely be opportune. This is purely out of curiosity of how timeout functions with DELETE.

Answer 1

The Oracle, SQL Server,MySQL, PostgreSQL databases follows ACID properties. Hence whenever delete statement shows timed-out it must get rolled back. You can get overview of ACID from the this Link.