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.
Fix Error “The function ‘RANK’ must have an OVER clause with ORDER BY” in SQL Server
When using window functions such as RANK() in SQL Server, we must provide an OVER clause clause with an ORDER BY clause.
If you’re getting an error that reads “The function ‘RANK’ must have an OVER clause with ORDER BY”, it’s probably because you’re including an OVER clause with the RANK() function (as is required), but you’re omitting the ORDER BY clause.
To fix this error, add an ORDER BY clause to the OVER clause.
An Introduction to SQL Server’s GROUPING_ID() Function
SQL 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.
A Quick Overview of UNION DISTINCT in SQL
If you’ve ever used the UNION clause in a SQL query, chances are you used UNION ALL or just UNION by itself. But some RDBMSs also accept a UNION DISTINCT option.
The UNION DISTINCT option is basically the equivalent of UNION by itself. That is, it removes redundant duplicate rows.
Fix Error “function lag(numeric, numeric) does not exist” in PostgreSQL
If you’re getting an error in PostgreSQL that reads something like “function lag(numeric, numeric) does not exist“, it could be because your second argument is the wrong data type.
The second argument to the lag() function is optional, but if it’s provided, it must be an integer.
So to fix this issue, make sure the second argument is an integer. Alternatively, you can omit the second argument altogether if you’re happy to use the default value of 1.
How to Limit the Rows Returned by a SQL Query
When writing SQL queries, we’ll often use a WHERE clause or HAVING clause to narrow the results down to just those rows that we’re interested in.
But sometimes we might want to reduce the number of rows returned without adding extra filtering criteria. Sometimes we might just want to see a handful of rows, without hundreds, thousands or even millions of rows being returned.
Understanding GROUPING SETS() in SQL Server
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.
How GROUP BY CUBE() Works in SQL Server
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.
Fix Error “The function ‘LEAD’ must have an OVER clause” in SQL Server
If you’re getting SQL Server error 10753 that reads “The function ‘LEAD’ must have an OVER clause”, it’s probably because you’re calling the LEAD() function without an OVER clause.
The LEAD() function requires an OVER clause (and that clause must have an ORDER BY clause).
To fix this issue, be sure to include an OVER clause when calling the LEAD() function.
Understanding GROUP BY ROLLUP() in SQL Server
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.