update문에 select 문 사용하기

UPDATE table_a
SET column_a = column_b
WHERE userid IN (SELECT userid
FROM b)

UPDATE table_a
SET (column_1, column__2) = (SELECT column_a, column_b
FROM table_b
WHERE join_column_1 = table_a.join_column_a);

UPDATE table_a
SET column_1 = (SELECT COLUMN
FROM table_b
WHERE userid = table_a.userid);

UPDATE table_a
SET (column_1) = (SELECT COLUMN
FROM table_b
WHERE userid = table_a.userid AND url IS NOT NULL);