SQL查找列的总和

Question

I have a table insurance with columns:

p_id smallint
2011_inv int
2012_inv int
city char(15)

I want to find out sum total of 2012_inv for all p_id where 2011_inv is equal but city name is different. Please help. I have been struggling with this all evening.

Refer to the table below

Answer 1

SELECT SUM(tiv_2012) FROM insurance
WHERE tiv_2011 = tiv_2012
AND city NOT 'value';

City is different from what? There needs to be a value for City for it to be different from something