Вы можете рассмотреть следующее:
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(id SERIAL PRIMARY KEY
,inning INT NOT NULL
,pitcher CHAR(3) NOT NULL
);
INSERT INTO my_table VALUES
(1,1,'AE1'),
(2,1,'AE1'),
(3,1,'AE1'),
(4,2,'AE1'),
(5,2,'AE1'),
(6,2,'AE2');
SELECT DISTINCT x.*
FROM my_table x
LEFT
JOIN my_table y
ON y.inning = x.inning
AND y.pitcher <> x.pitcher
AND y.id <> x.id
WHERE y.id IS NULL;
+----+--------+---------+
| id | inning | pitcher |
+----+--------+---------+
| 1 | 1 | AE1 |
| 2 | 1 | AE1 |
| 3 | 1 | AE1 |
+----+--------+---------+
3 rows in set (0.00 sec)