MySQL 5.6

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CREATE TABLE t( Id INT,	Owner VARCHAR(80), Company VARCHAR(80),	Job VARCHAR(10) )
INSERT INTO t VALUES
(1,'John Doe','Company 1','CEO'),
(1,'John Doe','Company 2','CEO'),
(1,'John Doe','Company 3','CEO'),
(1,'Gab Durand','Company 4','CEO'),
(1,'Rob Dujn','Company 5','CTO'),
(1,'Alex DoeMorse','Company 6','COO')
SELECT Id, Owner, company, Job,
       (SELECT COUNT(*) 
          FROM t 
         WHERE id = tt.id 
           AND Owner = tt.Owner ) AS count
  FROM t AS tt


Id
Owner
company
Job
count


1
John Doe
Company 1
CEO
3

1
John Doe
Company 2
CEO
3

1
John Doe
Company 3
CEO
3

1
Gab Durand
Company 4
CEO
1

1
Rob Dujn
Company 5
CTO
1

1
Alex DoeMorse
Company 6
COO
1

Id	Owner	company	Job	count
1	John Doe	Company 1	CEO	3
1	John Doe	Company 2	CEO	3
1	John Doe	Company 3	CEO	3
1	Gab Durand	Company 4	CEO	1
1	Rob Dujn	Company 5	CTO	1
1	Alex DoeMorse	Company 6	COO	1