Update specific records of MySQL table

Question

I am dealing with phone system and have to work with multiple service vendors. For one vendor I have a MySQL table country_codes like this -

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Answer 1

update cc set
    country_code = t.country_code
from country_codes cc
join (
    select country_code, country, char_length(trim(cast(country_code as char))) as code_len
    from country_codes
    where country_code <> 0
) t on 
    t.country_code = cast(substr(cast(cc.area_code as char), 1, t.code_len) as signed integer) and
    cc.country_code = 0 and
    cc.country like concat(t.country, '%')

I've added cc.country like concat(t.country, '%') to condition to be more specific but it assumes that each cellular network name starts with its country name - so if it's not true omit it.

Added after @Sachyn comment:

Test code used on SQLZOO works fine, it is for testing only, it's not an update query:

select cc.*, t.country_code as new_country_code
from (
    select 93 as country_code, 93  as area_code , 'Afghanistan' as country union
    select 0  , 9375 , 'Afghanistan Cellular-AT' union
    select 0  , 9370 , 'Afghanistan Cellular-AWCC' union
    select 355, 355  , 'Albania' union
    select 0  , 35568, 'Albania Cellular-AMC' union
    select 0  , 35567, 'Albania Cellular-Eagle' union
    select 213, 213  , 'Algeria' union
    select 0  , 21377, 'Algeria Cellular-Djezzy' union
    select 0  , 2135 , 'Algeria Cellular-Wataniya'
) cc
join (
    select country_code, country, char_length(rtrim(cast(country_code as char))) as code_len
    from (
        select 93 as country_code, 93  as area_code , 'Afghanistan' as country union
        select 0  , 9375 , 'Afghanistan Cellular-AT' union
        select 0  , 9370 , 'Afghanistan Cellular-AWCC' union
        select 355, 355  , 'Albania' union
        select 0  , 35568, 'Albania Cellular-AMC' union
        select 0  , 35567, 'Albania Cellular-Eagle' union
        select 213, 213  , 'Algeria' union
        select 0  , 21377, 'Algeria Cellular-Djezzy' union
        select 0  , 2135 , 'Algeria Cellular-Wataniya'
    ) c
    where country_code <> 0
) t on 
    t.country_code = cast(substr(cast(cc.area_code as char), 1, t.code_len) as signed integer) and
    cc.country_code = 0 and
    cc.country like concat(t.country, '%')