从一个sql表搜索并插入到另一个

Question

I have a table called places which has 2 million records. In these records there is a column called city_name .

In another table I have 2 columns: city_name and city_id .

My aim is to search the table cities with the city_name from the table places and insert the corresponding city_id from the table cities into the table places.

I have tried to use the following:

UPDATE places
INNER JOIN cities USING (city_name)
SET places.city_id = cities.city_id

The problem with this is that it has worked but i am having random city_id's in the city_id field that does not match the city name.

I should also mention that there might not be a corresponding city name in the table cities, so i want to ignore records that do not exist.

Can anyone help please. I am using phpmyadmin

Thank you

Answer 1

If I understand your request correctly the solution would be

UPDATE places
SET places.city_id = (SELECT cities.city_id
                      FROM cities
                      WHERE cities.city_name = places.city_name)