PostgreSQL has an aggregate function called array_agg() that allows us to generate an array from the result set of a query.
The function accepts an argument which is used to generate the array. This argument is typically the column that we want to use in order to populate the array.
Continue readingIn SQL Server the VARP() function returns the statistical variance for the population for all values in the specified expression.
In SQL Server the VAR() function returns the statistical variance of all values in the specified expression.
In SQL Server the STDEVP() function returns the statistical standard deviation for the population for all values in the specified expression.
In SQL Server the STDEV() function returns the statistical standard deviation of all values in a specified expression.
So we can use this function to get the standard deviation of all values in a column.
Continue readingSQL Server has a GROUPING_ID() function that returns the level of grouping based on its arguments.
We pass one or more column expressions to the function, and it computes the level of grouping. The column expressions must match the ones provided by the GROUP BY clause.
When using the GROUP BY clause in SQL Server, we can use the GROUPING SETS() option to combine multiple GROUP BY clauses into one GROUP BY clause. When we do this, the results are the equivalent of doing a UNION ALL of the specified groups.
SQL Server provides GROUP BY CUBE() functionality that we can use in our SQL queries, which creates groups for all possible combinations of columns.
It’s similar to the GROUP BY ROLLUP() functionality, except that it can provide us with more information, due to the fact that it groups all possible combinations.
When we use the GROUP BY clause in SQL Server, we have several options for specifying how the GROUP BY operation is applied. One such option is the ROLLUP modifier. We can use this modifier to create subtotals and grand totals.
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).