How to change in postgresql password of the user using SQL. I have user (alex) and his password (e.g. pass) i need to change using sql statement his password to NULL...
You will of course have to do this as a Postgres superuser.
Unfortunately, that doesn't let you log in with a blank password. You can only log in without a password if your pg_hba.conf entry specifies an auth type of 'trust' instead of 'md5' or 'password'.
So this SQL command is just cleaning up the password for a user that used to have one, but who is now trusted to get in without a password. You can't actually authenticate with a blank password. The distinction is slight.
The syntax for changing a user's password is