postgresql - SQL statements to replace specific cell data -

i want update data in specific cell. have googled , know need use update, of examples seeing show how change data in batches not single cell , don't want mess up.

so here example of answer table;

id | answer | user | location  1  | ans 1  | usr1 | loc 1 2  | ans 2  | usr2 | loc 2 3  | ans 3  | usr3 | loc 3 4  | ans 4  | usr4 | loc 4 

so if wanted change user usr3 usr2 in record 3, how write that?

thanks!

update answer set user = 'usr2' id = 3;