If you’re getting an error that reads “function ntile() does not exist” in PostgreSQL, it could be that you’re calling the ntile() function without any arguments.
This error message could be a bit misleading. The ntile() function does in fact exist (if you’re using PostgreSQL 8.4 or later), but the error occurs when we don’t provide an argument, or if we provide an argument of the wrong type.
In MySQL, we can use the LEAD() function to get the value of a subsequent row. For example we can get a value from the next row, or the one after that, and so on.
This enables us to do things like compute the difference between a value in the current row and a value in a following row. We can do this even if both values are in the same column.
Continue readingIf you’re getting an error that reads “window function nth_value requires an OVER clause” in PostgreSQL, it’s because you’re calling the nth_value() function without an OVER clause.
PostgreSQL requires that you include an OVER clause any time you call a built in nonaggregate window function such as nth_value().
To fix this issue, add an OVER clause to your window function.
MySQL 8.0.17 introduced a couple of functions that allow us to validate JSON documents against their schemas. These are listed below, with examples.
Continue readingIf you’re getting an error that reads “The function ‘CUME_DIST’ must have an OVER clause” when using SQL Server, it’s because you’re calling the CUME_DIST() function without an OVER clause.
The CUME_DIST() 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 CUME_DIST() function.
In PostgreSQL the lead() function returns the value from a subsequent row to the current row, specified by the given offset.
The offset specifies how many rows after the current row to get the value from. For example, an offset of 1 gets the value from the next row.
In PostgreSQL the lag() function returns the value from a previous row, specified by the given offset.
The offset specifies how many rows prior to the current row to get the value from. For example, an offset of 1 gets the value from the previous row.
In PostgreSQL the nth_value() function is a window function that returns the value from the given row of the current window frame. We provide the column and row number as an argument when we call the function.
In PostgreSQL, we can use the cume_dist() function to return the cumulative distribution of a value within a group of values.
It calculates this as follows: (the number of partition rows preceding or peers with current row) / (total partition rows).
The return value ranges from 1/N to 1.
In PostgreSQL, we can use the percent_rank() function to return the relative rank of each row, expressed as a percentage ranging from 0 to 1 inclusive.