In SQL Server, the GROUPING() function is used to distinguish the null values that are returned by ROLLUP, CUBE, or GROUPING SETS from standard null values.
Basically it tells us whether a specified column expression in a GROUP BY list is aggregated or not.
The GROUPING() function returns either 1 or 0 (1 indicates that the column expression is aggregated and 0 indicates that it’s not).
SQL Server has a CHECKSUM_AGG() function that allows us to get the checksum of the values in a group. This can be useful for detecting changes in the values in a column.
In SQL Server, the APPROX_PERCENTILE_DISC() function calculates and returns an approximate percentile based on a discrete distribution of the column values.
We pass the desired percentile to the function when we call it.
In SQL Server, the APPROX_PERCENTILE_CONT() function calculates and returns an approximate percentile based on a continuous distribution of the column value. This is an interpolated value from the set of values in a group based on percentile value and sort specification.
In SQL Server, the GREATEST() function returns the maximum value from a list of one or more expressions.
The GREATEST() function was introduced in SQL Server 2022 (along with the LEAST() function).
SQL Server 2022 introduced the LEAST() and GREATEST() functions, which allow us to get the minimum or maximum value from a list of expressions.
The LEAST() function returns the minimum value from a list of one or more expressions.
Most major RDBMSs support the DISTINCT clause, which allows us to get unique – or “distinct” – rows from our SQL queries. But PostgreSQL’s implementation of this clause has an extra option that most other RDBMSs don’t include.
PostgreSQL allows us to include the ON() option when using DISTINCT. This enables us to specify exactly which columns should be evaluated by the DISTINCT modifier, while simultaneously allowing us to return columns that aren’t evaluated.
Many SQL databases have a window function called NTILE() function that divides a rowset or partition into a given number of groups (buckets). The function typically returns the bucket number of the current row within its partition.
Most of the major relational database management systems (RDBMSs) allow for a DISTINCT clause to be included in our SQL queries.
We use the DISTINCT keyword to return only unique rows. It eliminates duplicates from the results. If we have two or more rows with exactly the same data, we’ll only see one row in the results.