patternsqlMinor
Is this a new common pattern in Oracle Where exists ( Select NULL FROM...)?
Viewed 0 times
thisfromnewnullwhereexistsselectoraclecommonpattern
Problem
Years ago, it was common to write
Last year I noticed that many t-sql scripts switched to using the number 1 instead of the star
just on SO I saw this Oracle example
Is this a common pattern with Oracle?
And which are the performance arguments to use something like this.
where exists (Select * from some_table where some_condition)Last year I noticed that many t-sql scripts switched to using the number 1 instead of the star
where exists (Select 1 from some_table where some_condition)just on SO I saw this Oracle example
WHERE EXISTS (SELECT NULL FROM ...Is this a common pattern with Oracle?
And which are the performance arguments to use something like this.
Solution
Short answer: I would hope not!
Even the
Even the
SELECT 1 idiom may have outlived its usefulness, as database engines have advanced enough to recognize that you don't really want the rows, you just want to know if the rows exist. I've looked at execution plans in SQL 2005, and have generally seen these re-written as joins, even where SELECT * is used.Context
StackExchange Database Administrators Q#287, answer score: 6
Revisions (0)
No revisions yet.