I am not able to update password in user table with update query. It shows "You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option ....".

It looks like your MySql session has the safe-updates option set. This means that you can't update or delete records without specifying a key (ex. primary key) in the where clause. 

You can run the below query to disable safe mode,

SET SQL_SAFE_UPDATES = 0;
 After this query try to run update password query in same table. Once operation completed, make sure you set it to default by running below command,

SET SQL_SAFE_UPDATES = 1;