docs/en/sql-reference/statements/alter/database-comment.md
Adds, modifies, or removes a database comment, regardless of whether it was set
before or not. The comment change is reflected in both system.databases
and the SHOW CREATE DATABASE query.
ALTER DATABASE [db].name [ON CLUSTER cluster] MODIFY COMMENT 'Comment'
To create a DATABASE with a comment:
CREATE DATABASE database_with_comment ENGINE = Memory COMMENT 'The temporary database';
To modify the comment:
ALTER DATABASE database_with_comment
MODIFY COMMENT 'new comment on a database';
To view the modified comment:
SELECT comment
FROM system.databases
WHERE name = 'database_with_comment';
┌─comment─────────────────┐
│ new comment on database │
└─────────────────────────┘
To remove the database comment:
ALTER DATABASE database_with_comment
MODIFY COMMENT '';
To verify that the comment was removed:
SELECT comment
FROM system.databases
WHERE name = 'database_with_comment';
┌─comment─┐
│ │
└─────────┘