![]() ![]() MySQL is the main database for, and back in the day, when a number of PlanetScale folks worked there, we had to do this kind of counting differently. It is clashing with other competing transactions. find shortest city name SET MinCityLen (SELECT MIN (CHARLENGTH (city)) FROM STATION) find longest city name SET MaxCityLen (SELECT MAX (CHARLENGTH (city)) FROM STATION) SELECT city, CHARLENGTH (city) FROM STATION WHERE find. In fact, until a recent version, you were guaranteed to get it sorted by the GROUP BY. Without the ORDER BY (ASC or DESC), you will probably get the output sorted by col. SELECT col, COUNT() FROM tbl GROUP BY col - no ORDER BY There definitely is an extra sort. You can see that this transaction has been waiting a significant amount of time to acquire a lock to increment the counter on this single row. mysql> SELECT pubid,GROUPCONCAT (DISTINCT cateid) -> FROM bookmast -> GROUP BY pubid -> ORDER BY GROUPCONCAT (DISTINCT cateid) ASC +-+-+ pubid GROUPCONCAT (DISTINCT cateid) +-+-+ P003 CA001,CA003 P005 CA001,CA004 P001 CA002,CA004 P0. Yours is not a case of a very simple query. SELECT col, COUNT() FROM tbl GROUP BY col ORDER BY COUNT() DESC versus. If you want descending order (as in this example), you use the DESC keyword. Record lock, heap no 2 PHYSICAL RECORD: n_fields 7 compact format info bits 0 As usual, you can use both ascending or descending order with ORDER BY. RECORD LOCKS space id 2 page no 4 n bits 184 index PRIMARY of table `github`.`downloads` trx id 79853106 lock_mode X locks rec but not gap waiting TRX HAS BEEN WAITING 5 SEC FOR THIS LOCK TO BE GRANTED: COUNT() can only be used with HAVING and must be used after GROUP BY statement Please find the following example: SELECT COUNT(), MDirector.PID FROM Movie INNER JOIN MDirector ON Movie.MID MDirector.MID GROUP BY MDirector. UPDATE slotted_counters SET count = count + 1 WHERE id = 1 MySQL thread id 24, OS thread handle 6281670656, query id 107 localhost root updating SQL ASC SQL ASC Keyword Previous SQL Keywords Reference Next ASC The ASC command is used to sort the data returned in ascending order. MySQL ORDER BY: with ASC attribute Let's take an example to retrieve the data in ascending order. LOCK WAIT 2 lock struct(s), heap size 1128, 1 row lock(s) ![]() When everything fits in RAM, the cost of the sort is minimal. But in either case, it will have to do some kind of sort at some point. InnoDB processes SELECT COUNT() statements by traversing the smallest available secondary index unless an index or optimizer hint directs the optimizer to use. TRANSACTION 79853106, ACTIVE 5 sec starting index read 1 Answer Sorted by: 1 The optimizer might build a hash table - key values of col, value count. As of MySQL 8.0.13, SELECT COUNT() FROM tblname query performance for InnoDB tables is optimized for single-threaded workloads if there are no extra clauses such as WHERE or GROUP BY. ![]()
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