MySQL in Count (), group by uses

Count () In the statistics table or in the array record

COUNT (*) returns the number of rows retrieved, regardless of whether the value contains null

COUNT (column_name) returns the count of rows that are NOT NULL for column column_name

For example, query the number of user comments for a recipe for an activity:

SELECT COUNT  from WHERE id=530787 and Idtype='paiid' 

Now you want to query the number of comments for each user and display them in reverse order of the number of comments:

SELECT COUNT  as  from WHERE id=530787 and Idtype='paiid' GROUP  by ORDER  by DESC

Of course, you can also query the number of comments more than 5:

  #在group by after using the HAVING clause to qualify the conditions for grouping 
 SELECT  count  (Authorid) as  C, authorid,author from  uchome_ Comment where  id530787  and  idtype=   '  

17:20:54 Continuous Update

MySQL in Count (), group by uses