sql - Update attribute only when value is not nil -

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i have simple sql statement:

update people  set (updated_at, first_name, last_name, email) =      (now(), r.first_name, r.last_name, r.email)  id = r.p_id;

i want set email value when r.email not nil.

is there way in 1 query?

i assume part of query

you need add conditional. depending on dbms (postgresql, mysql) need different solutions.

postgresql

you'll need coalesce. coalesce function returns first of arguments not null. 

update people set (updated_at, first_name, last_name, email) = (now(), r.first_name, r.last_name,      (coalesce (r.email, people.email))  people, r people.id = r.p_id

mysql

you'll need if condition:

if (r.email null, people.email, r.email)

so query need perform should similar to:

update people set (updated_at, first_name, last_name, email) = (now(), r.first_name, r.last_name,      (if (r.email null, people.email, r.email))  people, r people.id = r.p_id

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