SQL Server 2019

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CREATE TABLE player (
  player   NVARCHAR(32)
)
INSERT INTO
  player
VALUES
  ('A'),
  ('B'),
  ('C')
;

SELECT
  *
FROM
  player


player


A

B

C


SELECT
  l.player,
  r.player
FROM
  player   l
INNER JOIN
  player   r
    ON l.player < r.player
ORDER BY
  l.player,
  r.player


player
player


A
B

A
C

B
C


INSERT INTO
  player
VALUES
  ('D')
;

SELECT
  *
FROM
  player


player


A

B

C

D


SELECT
  l.player,
  r.player
FROM
  player   l
INNER JOIN
  player   r
    ON l.player < r.player
ORDER BY
  l.player,
  r.player


player
player


A
B

A
C

A
D

B
C

B
D

C
D