What happens internally when using SELECT INTO vs CREATE TABLE with temp tables

SELECT INTO dynamically creates the temp table and inserts data in a single operation. Internally it performs metadata creation and data loading together, uses TempDB heavily, and usually benefits from minimal logging, making it very fast for large bulk operations — but it does not create indexes, constraints, or statistics automatically, so plan stability is weaker.

CREATE TABLE + INSERT creates metadata first, then loads data. Inserts are fully logged, TempDB allocation is better controlled, statistics and indexes are supported, execution plans are more stable, and it supports temp table caching. This makes it better for OLTP, complex joins, and repeat execution scenarios.