UPDATE salary_detail
SET s_card = employer.s_card
FROM salary_detail, employer
WHERE salary_detail.static_no = employer.static_no
AND salary_detail.s_card is not NULL
SET s_card = employer.s_card
FROM salary_detail, employer
WHERE salary_detail.static_no = employer.static_no
AND salary_detail.s_card is not NULL
SET salary_detail.s_card = employer.s_card
FROM salary_detail, employer
WHERE salary_detail.static_no = employer.static_no AND salary_detail.s_card is not NULL
SET s_card = e.s_card
FROM salary_detail s, employer e
WHERE s.static_no = e.static_no AND s.s_card is not NULL