MySQL has a LAG() function that we can use to return the value of a previous row of our choosing, based on how many rows back it is from the current row.
Armed with that value, we can then calculate the difference between it and the current row’s value.
Continue readingIf you’re getting SQL Server error 10753 that reads “The function ‘NTILE’ must have an OVER clause”, it’s probably because you’re calling the NTILE() function without an OVER clause.
The NTILE() 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 NTILE() function.
If you’re getting error 245 that reads something like “Conversion failed when converting the varchar value ‘Five’ to data type int” when using the LEAST() or GREATEST() functions in SQL Server, it’s probably because your arguments aren’t of a comparable data type.
When using LEAST() and GREATEST(), all arguments must be of a data type that is comparable and that can be implicitly converted to the data type of the argument with the highest precedence.
To fix this issue, be sure to pass arguments of comparable data types.
Continue readingIf you have a query that returns multiple columns with numeric values in SQL Server, you can pass them to the GREATEST() function to find out which column has the highest value.
MySQL has a bunch of functions that enable us to get values from another row in the same column. This makes it easy for us to do stuff like calculate the difference between a value in the current row and one in another row, even if it’s in the same column.
Here are five options for calculating the difference between a value in the current row and a value in a different row but in the same column.
Continue readingIf you’re getting SQL Server error number 189 that reads “The greatest function requires 1 to 254 arguments“, it’s probably because you’re either passing too few or too many arguments.
As the error message alludes to, you need to pass at least 1 argument, and no more than 254 arguments when using the GREATEST() function.
To fix this issue, be sure to pass at least 1 argument, and no more than 254 arguments.
Continue readingIf you’re getting an error message that reads “The function ‘LAST_VALUE’ must have an OVER clause with ORDER BY.” when using the LAST_VALUE() function in SQL Server, it’s probably because you’ve omitted the ORDER BY clause from the OVER clause.
The LAST_VALUE() function requires an OVER clause that contains an ORDER BY clause. This error happens when we include the OVER clause but not the ORDER BY clause.
To fix this error, add an ORDER BY clause to the OVER clause.
Sometimes when we run a SQL query, we only want to see unique rows. But depending on the columns we’re selecting, we might end up with duplicate rows. And this could happen without even knowing it, especially with large data sets.
But it doesn’t have to be this way.
Fortunately most SQL databases provide us with an easy way to remove duplicates.
Continue readingIf you’re getting SQL Server error msg 402 that tells you the “data types” are “incompatible in the approx_percentile_cont operator“, it’s probably because you’re trying to apply the APPROX_PERCENTILE_CONT() function against a non-numeric column (or one that doesn’t evaluate to a numeric type).
When using the APPROX_PERCENTILE_CONT() function, the ORDER BY expression in the WITHIN GROUP clause must evaluate to an exact or approximate numeric type. Other data types are not allowed, and will result in the above error.
To fix this issue, be sure to apply the function against a numeric column/expression.
Continue readingIf you’re getting SQL Server error 10754 that reads “The function ‘APPROX_PERCENTILE_CONT’ must have a WITHIN GROUP clause” it’s probably because you’re calling the APPROX_PERCENTILE_CONT() function, but you’ve omitted the WITHIN GROUP clause.
To fix this issue, add a WITHIN GROUP clause to the function (and make sure it has an ORDER BY clause).