WITH common_subquery AS (
SELECT user_id, column1, column2
FROM shared_table
WHERE condition
)
SELECT user_id, column1, column2
FROM common_subquery
JOIN table1 ...
UNION
SELECT user_id, column1, column2
FROM common_subquery
JOIN table2 ...
WITH common_subquery AS (
SELECT user_id, column1, column2
FROM shared_table
WHERE condition
)
SELECT user_id, column1, column2
FROM common_subquery
JOIN table1 ...
UNION
SELECT user_id, column1, column2
FROM common_subquery
JOIN table2 ...