WebFeb 7, 2012 · Some changes that may improve the query: Change COUNT (id) to COUNT (*). Since id is (I guess) the PRIMARY KEY and NOT NULL, the results will be identical. Add an ORDER BY NULL after ther GROUP BY clause. In MySQL, a group by operation also sorts the results, unless you specify other wise. The (page_id, date_created) is probably … Web2 days ago · Using index for group-by:类似于访问表的Using index方式,Using index for group-by表示MySQL发现了一个索引,可以用来查 询GROUP BY或DISTINCT查询的所有 …
performance - Can an index speed up a query with GROUP BY…
WebJan 30, 2011 · Even if we add FORCE INDEX to the query on two indexes EXPLAIN will return the exact same thing. To make it collect across two indexes, and then intersect them, use this: select t.* from t1 as a force index (ix_t1_on_i) join t1 as b force index (ix_t1_on_j) on a.id=b.id where a.i=2 and b.j=3 or a.i=3 and b.j=2. Web# EXPLAIN ANALYZE SELECT a,b,sum(c) FROM foo GROUP BY a,b ORDER BY a,b; QUERY PLAN ----- GroupAggregate (cost=0.42..61292.04 rows=50 width=14) (actual … gold coast farm wedding
Understanding Indexes in MySQL: Part One Severalnines
WebMay 14, 2024 · The Benefits and Drawbacks of Using Indexes in MySQL. The main benefit of using indexes in MySQL is the increased performance of search queries matching a WHERE clause – indexes speed up SELECT queries matching a WHERE clause because MySQL doesn’t read through the entire table to find rows relevant to the query. However, … WebThe most efficient way to process GROUP BY is when an index is used to directly retrieve the grouping columns. With this access method, MySQL uses the property of some … WebNot likely. GROUP BY and ORDER BY typically entail a sort. However, in this case a HashAggregate is used (likely because we're working with the whole table).. CREATE TABLE foo AS SELECT x % 5 AS a, x % 10 AS b, x AS c FROM generate_series(1,1e6) AS x; With the HashAggregate plan, hcfcd wmd