No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

UPDATE customers SET countryCode = 'USA' WHERE country = 'USA'; -- which gives the error, you just write: UPDATE customers SET countryCode = 'USA' WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more. 

Now you can be assured every record is updated like you expect.

No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. SAFE_UPDATES is by default on for a REASON. You can drive a car without safety belts and other things if you know what I mean ;) Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

UPDATE customers SET countryCode = 'USA' WHERE country = 'USA'; -- which gives the error, you just write: UPDATE customers SET countryCode = 'USA' WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more. 

Now you can be assured every record is (ALWAYS) updated as you expect.

No need to set SAFE_SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way because:

it's very dangerous

when updating tables this way without sequencially using a key, that's the reason it's default 'ON' to protect you from making mistakes! Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

UPDATE customers SET countryCode = 'USA' WHERE country = 'USA'; -- which gives the error, you just write: UPDATE customers SET countryCode = 'USA' WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more. 

Now you can be assured every record is updated like you expect.

No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

UPDATE customers SET countryCode = 'USA' WHERE country = 'USA'; -- which gives the error, you just write: UPDATE customers SET countryCode = 'USA' WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more. 

Now you can be assured every record is updated like you expect.