Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance
Hashes a password and compares the hash to the hash of an existing password. PWDCOMPARE can be used to search for blank SQL Server login passwords or common weak passwords.
Transact-SQL syntax conventions
PWDCOMPARE ( 'clear_text_password' , password_hash [ , version ] )
To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation.
' clear_text_password '
Is the unencrypted password. clear_text_password is sysname (nvarchar(128)).
Is the encryption hash of a password. password_hash is varbinary(128).
Obsolete parameter that can be set to 1 if password_hash represents a value from a login earlier than SQL Server 2000 (8.x) that was migrated to SQL Server 2005 (9.x) or later but never converted to the SQL Server 2000 (8.x) system. version is int.
This parameter is provided for backwards compatibility, but is ignored because password hash blobs now contain their own version descriptions. This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.
Returns 1 if the hash of the clear_text_password matches the password_hash parameter, and 0 if it does not.
The PWDCOMPARE function is not a threat against the strength of password hashes because the same test could be performed by trying to log in using the password provided as the first parameter.
PWDCOMPARE cannot be used with the passwords of contained database users. There is no contained database equivalent.
PWDENCRYPT is available to public.
CONTROL SERVER permission is required to examine the password_hash column of sys.sql_logins.
A. Identifying logins that have no passwords
The following example identifies SQL Server logins that have no passwords.
SELECT name FROM sys.sql_logins WHERE PWDCOMPARE('', password_hash) = 1 ;
B. Searching for common passwords
To search for common passwords that you want to identify and change, specify the password as the first parameter. For example, execute the following statement to search for a password specified as
SELECT name FROM sys.sql_logins WHERE PWDCOMPARE('password', password_hash) = 1 ;