Date and time values are not entirely intuitive to aggregate into averages in T-SQL, although the business case does arguably exist. Suppose, for instance, that you have a production log with a “duration” column (in the “time” datatype), and you want to find the totalt or average duration for a certain group of items.
It’s possible, but I would still call it a workaround.
Continue readingThe “include actual execution plan” feature in SQL Server Management Studio is an invaluable tool for performance tuning. It returns the actual execution plan used for each statement, including actual row counts, tempdb spills and a lot of other information you need to do performance tuning.
But sometimes you want to run a series of statements or procedures where you only want the execution plan for some of the statements. Here’s how:
Whenever you’re building a data warehouse or similar solution, you’ll probably want to have a “calendar dimension”, a table that contains all days in a range of years. A challenge with this type of table is getting all the public holidays right, which could be particularly important if your business depends on this, like financial markets or logistics.
At one point or another, you’re going to come across intervals when working in SQL Server. You could say that an interval is where you don’t have a single value, but actually a range of values, commonly delimited within a start and an end value. This range could be a group of accounts, versions of dimension members (in an SCD) or date/time intervals.
sqlsunday.com 