Example (MySQL):

CREATE TABLE table1 (id INT, name VARCHAR(20), cats FLOAT);
CREATE TABLE table2 (id INT, age INTEGER);

SELECT id AS ID, name, cats, age
FROM (SELECT table1.id, name, cats, age
FROM table1
JOIN table2 ON table1.id = table2.id);

According to Derived Tables at dev.mysql.com, an alias is mandatory. You can add the alias by using the Introduce alias quick-fix.

After the quick-fix is applied:

SELECT id AS ID, name, cats, age
FROM (SELECT table1.id, name, cats, age
FROM table1
JOIN table2 ON table1.id = table2.id);