MySQL 5.7

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CREATE TABLE Score (
    round_id VARCHAR(50),
	team_id VARCHAR(50),
	score INT 
);

INSERT INTO Score  VALUES ('424d4186-4432-4b8d-ab9d-00ee71945cf6','752f9ebc-7016-42f2-be90-768711fc3d46',18);
INSERT INTO Score  VALUES ('424d4186-4432-4b8d-ab9d-00ee71945cf6','90dd8de4-8ddc-46cd-8b67-d93edbede174',7);
INSERT INTO Score  VALUES ('3fbb49a0-7a8a-4db5-b854-84a9ce7ac2b3','90dd8de4-8ddc-46cd-8b67-d93edbede174',20);
INSERT INTO Score  VALUES ('3fbb49a0-7a8a-4db5-b854-84a9ce7ac2b3','752f9ebc-7016-42f2-be90-768711fc3d46',21);

CREATE TABLE Teams (
    id VARCHAR(50),
	tournament_id VARCHAR(50)
);

INSERT INTO Teams  VALUES ('2b56a499-9fc4-40c2-a7c4-43762c2b27e7','9aaa6f86-5555-49b8-99a6-900a90dc3c7c');
INSERT INTO Teams  VALUES ('752f9ebc-7016-42f2-be90-768711fc3d46','9aaa6f86-5555-49b8-99a6-900a90dc3c7c');
INSERT INTO Teams  VALUES ('7c9aa32a-ff99-4169-9512-27bc0aac0093','9aaa6f86-5555-49b8-99a6-900a90dc3c7c');
INSERT INTO Teams  VALUES ('90dd8de4-8ddc-46cd-8b67-d93edbede174','9aaa6f86-5555-49b8-99a6-900a90dc3c7c');

team_id	COUNT(m_Score)
752f9ebc-7016-42f2-be90-768711fc3d46	2
90dd8de4-8ddc-46cd-8b67-d93edbede174	0