如何对后续行进行分组（基于标准）然后对它们进行计数[MySQL]？

Question

Let's say I have such a table (ordered by date):

id | name | type  | date 
 1 | A    | 1     | 01-08-2012
 2 | A    | 2     | 01-08-2012
 3 | B    | 1     | 02-09-2012
 4 | A    | 1     | 01-10-2012
 5 | A    | 4     | 01-10-2012
 6 | A    | 5     | 02-10-2012

I want to group subsequent rows that have the same 'name' value and count them:

name | count 
A    | 2
B    | 1
A    | 3

I was thinking about writing a stored procedure and using cursors, but I was also wondering, if there's a simpler solution, for example using nested SELECTs, etc.

My question is very similar to: how to group array and count them , but that one concerns PHP.

Answer 1

To do that I used a couple of variables, the table structure, I created my own just for testing and it's:

create table abc (id int, name varchar(20),type int);

insert into abc values 
( 1 , 'A'    , 1  ),
( 2 , 'A'    , 2 ),
( 3 , 'B'    , 1  ),
( 4 , 'A'    , 1  ),
( 5 , 'A'    , 4  ),
( 6 , 'A'    , 5  )

the query ended being like this:

set @a:='';
set @counter:=1;
set @groupby:=0;
select *,count(REPEATED) from (select name,if(@a=name,@counter:=@counter+1,@counter:=1) as rep,if(@counter=1,@groupby:=@groupby+1,@groupby) as repeated,@a:=name type from abc) as t group by repeated

you can see it works in SQLFIDDLE if you have any question let me know.

In the SQLFIDDLE