在继承情况下使用UNION with JOIN - MySQL

CREATE TABLE parent (
  id INT PRIMARY KEY,
  common_field VARCHAR(50)
);

CREATE TABLE child1 (
  id INT PRIMARY KEY,
  child1_field VARCHAR(50),
  FOREIGN KEY (id) REFERENCES parent(id)
);

CREATE TABLE child2 (
  id INT PRIMARY KEY,
  child2_field VARCHAR(50),
  FOREIGN KEY (id) REFERENCES parent(id)
);

SELECT parent.id, parent.common_field, child1.child1_field, NULL AS child2_field
FROM parent
JOIN child1 ON parent.id = child1.id
UNION
SELECT parent.id, parent.common_field, NULL AS child1_field, child2.child2_field
FROM parent
JOIN child2 ON parent.id = child2.id;