How to group continuous ranges using MySQL - mysql

Question

I have a table that contains categories, dates and rates. Each category can have different rates for different dates, one category can have only one rate at a given date.
Id CatId Date Rate
------ ------ ------------ ---------
000001 12 2009-07-07 1
000002 12 2009-07-08 1
000003 12 2009-07-09 1
000004 12 2009-07-10 2
000005 12 2009-07-15 1
000006 12 2009-07-16 1
000007 13 2009-07-08 1
000008 13 2009-07-09 1
000009 14 2009-07-07 2
000010 14 2009-07-08 1
000010 14 2009-07-10 1
Unique index (catid, Date, Rate)
I would like for each category to group all continuous dates ranges and keep only the begin and the end of the range.
For the previous example, we would have:
CatId Begin End Rate
------ ------------ ------------ ---------
12 2009-07-07 2009-07-09 1
12 2009-07-10 2009-07-10 2
12 2009-07-15 2009-07-16 1
13 2009-07-08 2009-07-09 1
14 2009-07-07 2009-07-07 2
14 2009-07-08 2009-07-08 1
14 2009-07-10 2009-07-10 1
I found a similar solution in the forum which did not exactly give the result
WITH q AS
(
SELECT *,
ROW_NUMBER() OVER (PARTITION BY CatId, Rate ORDER BY [Date]) AS rnd,
ROW_NUMBER() OVER (PARTITION BY CatId ORDER BY [Date]) AS rn
FROM my_table
)
SELECT CatId AS catidd, MIN([Date]) as beginn, MAX([Date])as endd, Rate
FROM q
GROUP BY CatId, rnd - rn, Rate
SEE SQL FIDDLE
How can I do the same thing in mysql?
Please help!

Answer 1

MySQL doesn't support analytic functions, but you can emulate such behaviour with user-defined variables:
SELECT CatID, Begin, MAX(Date) AS End, Rate
FROM (
SELECT my_table.*,
#f:=CONVERT(
IF(#c<=>CatId AND #r<=>Rate AND DATEDIFF(Date, #d)=1, #f, Date), DATE
) AS Begin,
#c:=CatId, #d:=Date, #r:=Rate
FROM my_table JOIN (SELECT #c:=NULL) AS init
ORDER BY CatId, Rate, Date
) AS t
GROUP BY CatID, Begin, Rate
See it on sqlfiddle.

Answer 2

SELECT catid,min(ddate),max(ddate),rate
FROM (
SELECT
Catid,
Ddate,
rate,
#rn := CASE WHEN (#prev <> rate
or DATEDIFF(ddate, #prev_date)>1) THEN #rn+1 ELSE #rn END AS rn,
#prev := rate,
#prev_id := catid ,
#prev_date :=ddate
FROM (
SELECT CatID,Ddate,rate
FROM rankdate
ORDER BY CatID, Ddate ) AS a ,
(SELECT #prev := -1, #rn := 0, #prev_id:=0 ,#prev_date:=-1) AS vars
) T1 group by catid,rn
Note: The line (SELECT #prev := -1, #rn := 0, #prev_id:=0 ,#prev_date:=-1) AS vars is not necessary in Mysql Workspace, but it is in the PHP mysql_query function.
SQL FIDDLE HERE

Answer 3

I know I am late, still posting a solution that worked for me.
Had the same issue, here's how I got it
Found a good solution using variables
SELECT MIN(id) AS id, MIN(date) AS date, MIN(state) AS state, COUNT(*) cnt
FROM (
SELECT #r := #r + (#state != state OR #state IS NULL) AS gn,
#state := state AS sn,
s.id, s.date, s.state
FROM (
SELECT #r := 0,
#state := NULL
) vars,
t_range s
ORDER BY
date, state
) q
GROUP BY gn
More details at : https://explainextended.com/2009/07/24/mysql-grouping-continuous-ranges/