如何对后续行进行分组(基于标准)然后对它们进行计数 [MySQL]?
假设我有一个这样的表(按日期排序):
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
我想对具有相同名称"值的后续行进行分组并对其进行计数:
I want to group subsequent rows that have the same 'name' value and count them:
name | count
A | 2
B | 1
A | 3
我正在考虑编写一个存储过程并使用游标，但我也想知道是否有更简单的解决方案，例如使用嵌套的 SELECT 等.
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.
我的问题非常类似于:如何对数组进行分组和计数，但那个是关于 PHP 的.
My question is very similar to: how to group array and count them, but that one concerns PHP.
推荐答案
为此我使用了几个变量，表结构，我创建自己的只是为了测试，它是:
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 )
查询结束是这样的:
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
您可以在 SQLFIDDLE 中看到它的工作原理，如果您有任何问题，请告诉我知道.
you can see it works in SQLFIDDLE if you have any question let me know.
在 SQLFIDDLE 中
In the SQLFIDDLE
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