Question

Timezones
---------
-AreaCode varchar
-Timezone varchar

Contacts
--------
-Phone    varchar
-Timezone varchar

Everything is populated except Timezone in the Contacts table, so I want to lookup the timezone for each phone number and update the contacts. Here’s what I tried to do, but MySQL gives

Error 1242 Subquery returns more than one row

For each timezone (0,-1,-2,-3,-4,-5), I execute this update:

update contacts 
set contacts.timezone = '-1' 
where left(contacts.phone,3) = (Select timezones.areacode 
                                from timezones 
                                where timezones.timezone = '-1');

Answer 1

Your subquery returns more than one row. Just replace “=” with “IN” to handle this issue:

update contacts 
set contacts.timezone = '-1' 
where left(contacts.phone,3) in (Select timezones.areacode 
                                from timezones 
                                where timezones.timezone = '-1');