SQL tournament date generator - sql

Question

I am trying to create a tournament where in each team will play each other once both home and away.
I want to generate a date so that each Friday the teams will play one another
TempExampletable shows what the end result will look like with each team playing once per week.
TempExampletable2 shows the data I currently have and what I will be using to generate the date.
DROP TABLE TempExampletable;
DROP TABLE TempExampletable2;
CREATE TABLE TempExampletable(
Home VARCHAR(100),
Away VARCHAR (100),
Playing DATETIME
)
INSERT INTO TempExampletable VALUES
('Team 1', 'Team 2', '2017/12/01 17:30:00'),
('Team 1', 'Team 3', '2017/12/08 17:30:00'),
('Team 1', 'Team 4', '2017/12/15 17:30:00'),
('Team 2', 'Team 1', '2017/12/22 17:30:00'),
('Team 2', 'Team 3', '2017/12/15 17:30:00'),
('Team 2', 'Team 4', '2017/12/08 17:30:00'),
('Team 3', 'Team 1', '2017/12/29 17:30:00'),
('Team 3', 'Team 2', '2018/11/05 17:30:00'),
('Team 3', 'Team 4', '2017/12/01 17:30:00'),
('Team 4', 'Team 1', '2018/01/05 17:30:00'),
('Team 4', 'Team 2', '2017/12/29 17:30:00'),
('Team 4', 'Team 3', '2017/12/22 17:30:00')
CREATE TABLE TempExampletable2(
Home VARCHAR(100),
Away VARCHAR (100),
Playing DATETIME
)
INSERT INTO TempExampletable2(Home, Away) VALUES
('Team 1', 'Team 2'),
('Team 1', 'Team 3'),
('Team 1', 'Team 4'),
('Team 2', 'Team 1'),
('Team 2', 'Team 3'),
('Team 2', 'Team 4'),
('Team 3', 'Team 1'),
('Team 3', 'Team 2'),
('Team 3', 'Team 4'),
('Team 4', 'Team 1'),
('Team 4', 'Team 2'),
('Team 4', 'Team 3')
SELECT * FROM TempExampletable2 ORDER BY Playing ASC;
SELECT * FROM TempExampletable ORDER BY Playing ASC;

Answer 1

Here is a solution. Please format the date as you like or you can insert into a datetime column
WITH teams AS
(SELECT Home, Away,
row_number() over(order by Home, Away) - 1 AS r_num
FROM TempExampletable2 )
SELECT Home, Away, DATEADD(week, r_num, '2017/12/01 17:30:00') AS Playing
FROM teams
ORDER BY Playing ASC;
Output
Home Away Playing
Team 1 Team 2 2017-12-01T17:30:00Z
Team 1 Team 3 2017-12-08T17:30:00Z
Team 1 Team 4 2017-12-15T17:30:00Z
Team 2 Team 1 2017-12-22T17:30:00Z
Team 2 Team 3 2017-12-29T17:30:00Z
Team 2 Team 4 2018-01-05T17:30:00Z
Team 3 Team 1 2018-01-12T17:30:00Z
Team 3 Team 2 2018-01-19T17:30:00Z
Team 3 Team 4 2018-01-26T17:30:00Z
Team 4 Team 1 2018-02-02T17:30:00Z
Team 4 Team 2 2018-02-09T17:30:00Z
Team 4 Team 3 2018-02-16T17:30:00Z

Answer 2

You know that because there are 4 teams involved, there are 2 matchups per week. If, within a given week, you schedule one matchup you know the second matchup cannot involve either of the participants from the first. (Team 1 can't play Team 2 and Team 3 at the same time, regardless of Home/Away decisions) This scenario makes it difficult to handle this in a set based approach where you'd be making use of Recursive CTE's or other methods.
The above is why I have written a double nested while loop to schedule the tournament season. The first loop for going week by week, and the second scheduling a matchup in each iteration.
Sample Data:
I simplified the sample data down to a list of the teams, and later create the matchups shown in your TempExampletable2
create table #team_table
(
Team char(6) not null
)
insert into #team_table
values ('Team 1')
, ('Team 2')
, ('Team 3')
, ('Team 4')
Answer:
create table #matchups
(
Home char(6) not null
, Away char(6) not null
)
create table #schedule
(
Home char(6) not null
, Away char(6) not null
, Playing datetime not null
)
insert into #matchups
select h.Team as Home
, a.Team as Away
from #team_table as h
cross join #team_table as a
where 1=1
and h.Team <> a.Team
declare #bgn_dt datetime = '2017-12-01 17:30:00'
, #tm_cnt int = (select count(*) from #team_table)
, #i int = 1
, #j int
, #j_max int
, #wk_cnt int
, #rnd int
, #cur_dt datetime;
set #wk_cnt = ((#tm_cnt * (#tm_cnt - 1)) / 2)
set #j_max = (#tm_cnt / 2) --games in a week
while #i <= #wk_cnt
begin --while i
set #cur_dt = dateadd(d, 7 * (#i - 1), #bgn_dt)
set #j = 1
while #j <= #j_max
begin
; with sched_teams as
(
select s.Home as Team
from #schedule as s
where 1=1
and s.Playing = #cur_dt
union all
select s.Away as Team
from #schedule as s
where 1=1
and s.Playing = #cur_dt
)
insert into #schedule
select top 1 m.Home
, m.Away
, #cur_dt as Playing
from #matchups as m
left join sched_teams as sh on m.Home = sh.Team --same team can't play 2 games in a single week
left join sched_teams as sa on m.Away = sa.Team --same team can't play 2 games in a single week
left join #schedule as s on m.Home = s.Home --can't play the same matchup twice
and m.Away = s.Away
where 1=1
and sh.Team is Null
and sa.Team is Null
and s.Home is Null
and s.Away is Null
order by m.Home asc
, m.Away asc
set #j += 1
end
set #i += 1
end --while i
select *
from #schedule
order by Home
, Away
The order by on the insert...select statement is only there to force the output to be the same as the expected output specified in TempExampletable.