In SQL Server, the ALL operator can be used with a subquery to compare a scalar value with a single-column set of values returned by the subquery.
It’s also true that the SELECT clause and UNION operator both accept an ALL argument, although this usage has a different purpose (allows duplicates in the result set).
Below are examples of using the ALL operator with a subquery.
Comparison operators are an important part of most programming languages.
Comparison operators are used to compare two expressions. The result is either true or false. It could also be unknown. This could also be represented by either 1, 0, or NULL, depending on the language. These are typically known as “Boolean expressions”.
When used with databases, comparison operators can be used inside your SQL queries to filter data to a certain criteria.
Continue readingIn SQL Server, the ANSI_NULLS setting allows you to specify how NULL values are treated in queries.
More specifically, it allows you to specify ISO compliant behaviour of the Equal To (=) and Not Equal To (<>) comparison operators when they are used with NULL values.
SQL Server has an ANSI_NULLS setting that determines how NULL values are evaluated when compared to another value with the Equals (=) and Not Equal To (<>) comparison operators.
While it’s true that you can change the ANSI_NULLS setting at the session level (using SET ANSI_NULLS), each database also has its own ANSI_NULLS setting.
You can check your database to see whether its ANSI_NULLS setting is ON or OFF.
To do this with T-SQL, you can either use the sys.databases catalog view or the DATABASEPROPERTYEX() function.
In SQL Server, you can use the sysmail_help_status_sp stored procedure on the msdb database to check the status of the Database Mail queues.
If you use Database Mail in SQL Server, you can use the sysmail_sentitems view to return a list of all emails that Database Mail has sent.
If you use Database Mail in SQL Server, you can use the sysmail_allitems view to check the status of all emails that Database Mail has processed.
If you’re trying to send email using Database Mail in SQL Server, but it fails to send, you can check the sysmail_event_log view to see why it failed.
The sysmail_event_log view returns one row for each Windows or SQL Server message returned by the Database Mail system. By “message”, I don’t mean the actual mail message. I mean a message such as the error message that explains why the mail failed.
You can also use the sysmail_configure_sp stored procedure to determine what types of messages are logged.
If you’re trying to send mail with SQL Server but it’s not being delivered, try checking the sysmail_faileditems view.
When sending emails from SQL Server, you can check for any unsent mail with the sysmail_unsentitems view.