postgresql ：ERROR: role “user001“ cannot be dropped because some objects depend on it

1.创建用户user001

CREATE USER user001 WITH PASSWORD '123456';
ALTER ROLE user001 CREATEROLE CREATEDB;

GRANT ALL PRIVILEGES ON DATABASE testdb TO username;

2.postgres 管理员删除用户user001 报错

DROP user user001

ERROR: role “user001” cannot be dropped because some objects depend on it
DETAIL: owner of database dbname

3.解决办法

revoke all on database databasename from user001;
DROP user user001

4.如果数据库是user001用户创建的

alter database testdb owner to postgres
DROP user user001