Question

Considering the following table:

someId INTEGER #PK
ageStart TINYINT(3)
ageEnd TINYINT(3)
dateBegin INTEGER
dateEnd INTEGER

Where dateBegin and dateEnd are dates represented as days since 1800-12-28…

And considering some sample data:

someId | ageStart | ageEnd | dateStart | dateEnd
------------------------------------------------
   203 |       16 |     25 |     76533 |   76539   \
   506 |       16 |     25 |     76540 |   76546    adjacent rows
   384 |       16 |     25 |     76547 |   76553   /
   342 |       16 |     25 |     76563 |   76569   \
   545 |       16 |     25 |     76570 |   76576    adjacent rows
   764 |       16 |     25 |     76577 |   76583   /

(There would be arbitrary rows mixed in off course, I just want to illustrate 2 relevant rowsets)

Is it possible to find adjacent rows for a given age category (ageStart to ageEnd) without a stored procedure? The criteria for adjacency is: dateStart is 1 day after dateEnd of the previous found row.

For instance, given the above sample data, if I were to query it with the following parameters:

ageStart = 16
ageEnd = 25
dateStart = 76533

I would like it to return me the rows 1, 2 and 3 of the sample data, since their dates are adjacent (dayStart is next day of previous row’s dateEnd).

ageStart = 16
ageEnd = 25
dateStart = 76563

…would give me rows 4, 5 and 6 of the sample data

Answer 1

Probably not efficient if lots of data into your table but try this:

SELECT b.*
FROM
(SELECT @continue:=2) init,
(
 SELECT * 
 FROM ageTable 
 WHERE ageStart=16 AND 
       ageEnd=25   AND 
       dateStart=76533
) a 
  INNER JOIN (
   SELECT *
   FROM ageTable
   ORDER BY dateStart
  ) b ON (
    b.ageStart=a.ageStart AND
    b.ageEnd=a.ageEnd     AND
    b.dateStart>=a.dateStart
  ) 
  LEFT JOIN ageTable c ON (
    c.dateStart=b.dateEnd+1 AND
    c.ageStart=b.ageStart   AND 
    c.ageEnd=b.ageEnd
  )
WHERE 
 CASE
  WHEN @continue=2 THEN
   CASE
    WHEN c.someId IS NULL THEN
     @continue:=1
    ELSE
     @continue
   END
  WHEN @continue=1 THEN
   @continue:=0
  ELSE
   @continue
 END