MySQL 5.7

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select version();


version()


5.7.27


CREATE TABLE  tab
(
  t_id    INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
  t_key   INTEGER NOT NULL,
  t_name  VARCHAR(10) NOT NULL,
  t_value VARCHAR(10) NOT NULL
);
INSERT INTO tab (t_key, t_name, t_value)
VALUES




(85, 'Color',  'Red'),
(85, 'Size',   'Big'),
(85, 'Weight', '6'),


(86, 'Color',  'Red'),
(86, 'Size',   'Big'),
(86, 'Weight', '6'),

(87, 'Color',  'Red'),
(87, 'Size',   'Small'),
(87, 'Weight', '7');

SELECT t1.t_key AS "t1key", t1.t_name AS "t1name", t1.t_value AS "t1value",
       t2.t_key AS "t2key", t2.t_name AS "t2name", t2.t_value AS "t2value"
FROM tab t1
JOIN tab t2
ON t1.t_key != t2.t_key
  AND t1.t_name = t2.t_name
  AND t1.t_value = t2.t_value
ORDER BY t1.t_id, t2.t_id;


t1key
t1name
t1value
t2key
t2name
t2value


85
Color
Red
86
Color
Red

85
Color
Red
87
Color
Red

85
Size
Big
86
Size
Big

85
Weight
6
86
Weight
6

86
Color
Red
85
Color
Red

86
Color
Red
87
Color
Red

86
Size
Big
85
Size
Big

86
Weight
6
85
Weight
6

87
Color
Red
85
Color
Red

87
Color
Red
86
Color
Red


SELECT 
  DISTINCT LEAST(t1key, t2key) AS "lst", 
        GREATEST(t1key, t2key) AS "gst",
    COUNT(LEAST(t1key, t2key)) AS "mn_c",
    COUNT(GREATEST(t1key, t2key)) AS "mx_c"
FROM
(

  SELECT t1.t_key AS "t1key", t1.t_name AS "t1name", t1.t_value AS "t1value",
         t2.t_key AS "t2key", t2.t_name AS "t2name", t2.t_value AS "t2value"
  FROM tab t1
  JOIN tab t2
  ON t1.t_key != t2.t_key
    AND t1.t_name = t2.t_name
    AND t1.t_value = t2.t_value
  ORDER BY t1.t_id, t2.t_id
)
AS t1
GROUP BY t1.t1key, t1.t2key
ORDER BY 1, 2, 3;


lst
gst
mn_c
mx_c


85
86
3
3

85
87
1
1

86
87
1
1


SELECT 
  DISTINCT LEAST(t1key, t2key) AS "lst", 
        GREATEST(t1key, t2key) AS "gst",
  COUNT(LEAST(t1key, t2key)) AS "mn_c"  -- << NOT NECESSARY - SHOWS NO. OF DUPS
  -- COUNT(GREATEST(t1key, t2key)) AS mx_c
FROM
(

  SELECT t1.t_key AS "t1key", t1.t_name AS "t1name", t1.t_value AS "t1value",
         t2.t_key AS "t2key", t2.t_name AS "t2name", t2.t_value AS "t2value"
  FROM tab t1
  JOIN tab t2
  ON t1.t_key != t2.t_key
    AND t1.t_name = t2.t_name
    AND t1.t_value = t2.t_value
  ORDER BY t1.t_id, t2.t_id
)
AS t1
GROUP BY t1.t1key, t1.t2key
HAVING
COUNT(LEAST(t1key, t2key)) 
  = (SELECT COUNT(tab.t_key) FROM tab WHERE t_key = t1.t1key)
AND
COUNT(GREATEST(t1key, t2key))
  = (SELECT COUNT(tab.t_key) FROM tab WHERE t_key = t1.t2key)
ORDER BY 1, 2;



lst
gst
mn_c


85
86
3

t1key	t1name	t1value	t2key	t2name	t2value
85	Color	Red	86	Color	Red
85	Color	Red	87	Color	Red
85	Size	Big	86	Size	Big
85	Weight	6	86	Weight	6
86	Color	Red	85	Color	Red
86	Color	Red	87	Color	Red
86	Size	Big	85	Size	Big
86	Weight	6	85	Weight	6
87	Color	Red	85	Color	Red
87	Color	Red	86	Color	Red