By Is GROUP BY faster than distinct Postgres?
GROUP-BY is anyway not worse than DISTINCT, and it is better sometimes.
Is distinct faster than GROUP BY MySQL?
DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the distinct results afterwards. is faster, if you don’t have an index on profession .
Is GROUP BY faster than distinct?
DISTINCT is used to filter unique records out of all records in the table. It removes the duplicate rows. SELECT DISTINCT will always be the same, or faster than a GROUP BY.
Why GROUP BY is faster than distinct?
DISTINCT would usually be faster than GROUP BY if a) there’s no index on that column and b) you are not ordering as well since GROUP BY does both filtering and ordering.
Should I use GROUP BY or distinct?
If you want to group your results, use GROUP BY, if you just want a unique list of a specific column, use DISTINCT. This will give your database a chance to optimise the query for your needs. Please don’t use GROUP BY when you mean DISTINCT, even if they happen to work the same.
Can I use distinct in GROUP BY?
Distinct is used to find unique/distinct records where as a group by is used to group a selected set of rows into summary rows by one or more columns or an expression. The functional difference is thus obvious. The group by can also be used to find distinct values as shown in below query.
Is GROUP BY or distinct better?
In MySQL, DISTINCT seems a bit faster than GROUP BY if theField is not indexed. DISTINCT only eliminate duplicate rows but GROUP BY seems to sort them in addition.
Can you use distinct in GROUP BY?
Well, GROUP BY and DISTINCT have their own use. GROUP BY cannot replace DISTINCT in some situations and DISTINCT cannot take place of GROUP BY. It is as per your choice and situation how you are optimizing both of them and choosing where to use GROUP BY and DISTINCT.
Does distinct reduce performance?
Your EXPLAIN shows 2,491 distinct users out of half a million qualifying rows. This won’t become super-fast, no matter what you do, but it can be substantially faster.
What’s the difference in performance between MySQL and Postgres?
This article is technical comparison between PostgreSQL vs MYSQL performance. PostgreSQL really is SQL compliant unlike MySQL. PostgreSQL better implements a lot of the things that oracle does in an open source environment even though MySQL is owned by oracle.
What does distinct on in PostgreSQL do?
The docs explain DISTINCT ON: SELECT DISTINCT ON ( expression [, …] ) keeps only the first row of each set of rows where the given expressions evaluate to equal And the reason I haven’t heard about it is: DISTINCT ON ( … ) is an extension of the SQL standard. PostgreSQL does all the heavy lifting for us.
Which is faster group by or distinct in Postgres?
Group by is expensive than Distinct since Group by does a sort on the result while distinct avoids it. But if you want to make group by yield the same result as distinct give order by null .. well distinct can be slower than group by on some occasions in postgres (dont know about other dbs).
Can you use distinct and group by together in MySQL?
The insane ability to allow partial group by in older versions of MySQL, has to be one top contender for most caused confusion in the it industry. could mean (1,1) or (1,2) and MySQL would randomly return one of these. DISTINCT does not matter in this case, the result is still in-deterministic.