MySQL 5.7

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CREATE TABLE user (
    user_id BINARY(16) PRIMARY KEY NOT NULL,
    first_name VARCHAR(25) NOT NULL, 
    last_name VARCHAR(25) NOT NULL
)
INSERT INTO user VALUES (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", "-","")),
    "Jon",
    "Smith"), (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-005056907767", "-","")),
    "Jane",
    "Doe");
SELECT * FROM user WHERE user_id = UNHEX(CONCAT(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", '-', '')))


user_id
first_name
last_name


null
Jon
Smith


CREATE TABLE summary (
    user_id BINARY(16) PRIMARY KEY NOT NULL,
    risk_score INT, 
    counted INT
)
INSERT INTO summary VALUES (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", "-","")),
    35,
    200), (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-005056907767", "-","")),24, 100);
SELECT * FROM summary WHERE user_id = UNHEX(CONCAT(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", '-', '')))


user_id
risk_score
counted


null
35
200


SELECT * 
FROM user
LEFT JOIN summary using(user_id) WHERE user.user_id = UNHEX(REPLACE("3f06af63-a93c-11e4-9797-005056907767", "-",""))


user_id
first_name
last_name
risk_score
counted


null
Jane
Doe
24
100


CREATE TABLE test (
    user_id BINARY(16) PRIMARY KEY NOT NULL,
    age INT, 
    likes INT
)
INSERT INTO test VALUES (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", "-","")),
    30,
    202), (UNHEX(REPLACE("3f06af63-a93c-11e4-9797-005056907767", "-","")),14, 150);
SELECT * FROM test WHERE user_id = UNHEX(CONCAT(REPLACE("3f06af63-a93c-11e4-9797-00505690773f", '-', '')))


user_id
age
likes


null
30
202


SELECT * 
FROM user
JOIN summary ON summary.user_id = user.user_id 
LEFT JOIN test ON test.user_id = summary.user_id


user_id
first_name
last_name
user_id
risk_score
counted
user_id
age
likes


null
Jon
Smith
null
35
200
null
30
202

null
Jane
Doe
null
24
100
null
14
150

user_id	first_name	last_name	user_id	risk_score	counted	user_id	age	likes
null	Jon	Smith	null	35	200	null	30	202
null	Jane	Doe	null	24	100	null	14	150