Normally if we try to insert data that violates a CHECK constraint in MySQL, we get an error, and the whole INSERT operation fails (including any conforming rows).
But it’s possible to change this, so that any conforming rows are inserted, and only the non-conforming rows are skipped.
We can do this by using the IGNORE clause.
In PostgreSQL the last_value() function returns the value from the last row of the current window frame.
There are at least a couple of reasons you might get an error that reads “function nth_value(numeric) does not exist” in PostgreSQL.
It could be that you’re calling the nth_value() function without the correct number of arguments. It could also be that you’re passing the wrong argument type.
To fix this issue, be sure to pass the correct number of arguments, with the correct type.
Continue readingIn PostgreSQL the first_value() function returns the value from the first row in the current window frame.
We can use this function to get the value from the first row in a result set, or from the first row in the current partition, or some other window frame that’s been specified.
Continue readingIf you’re getting an error that reads “ERROR: invalid input syntax for type integer” in PostgreSQL, it’s probably because you’re calling the ntile() function with an argument of the wrong data type.
This error can occur when we pass the wrong type to the ntile() function. We can get a different error depending on the type, but this error can occur when we pass a string.
To fix this issue, be sure to pass a positive integer to the function.
Continue readingIn SQL Server, if you’re getting an error that reads “The function ‘PERCENT_RANK’ must have an OVER clause”, it’s because you’re calling the PERCENT_RANK() function without an OVER clause.
The PERCENT_RANK() 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 PERCENT_RANK() function.
Most of the major RDBMSs allow us to create window functions in SQL queries.
A window function is a special aggregate-like function that enables partitioning and ordering of data within a result set. Unlike regular aggregate functions, which collapse multiple rows into a single result, window functions retain individual rows in the output, augmenting them with additional computed values.
The following example demonstrates how to create a window function in SQL.
Continue readingIn SQL Server, LEAD() is a window function that allows us to access a value from a later row in the same result set, without the need to perform a self-join.
We specify the row as an offset from the current row. An offset of 1 means it gets the value from the next row, an offset of 2 means two rows forward, and so on.
If you’re getting an error that reads “The function ‘ROW_NUMBER’ must have an OVER clause with ORDER BY” in SQL Server, it’s probably because you’re calling the ROW_NUMBER() function without an ORDER BY clause.
Window functions such as ROW_NUMBER() require an OVER clause, and that clause must have an ORDER BY clause. If you’re getting the above error, there’s a good chance you’re providing an OVER clause, but you’re omitting the ORDER BY clause.
To fix this issue, add an ORDER BY clause to the OVER clause when calling the ROW_NUMBER() function.
In SQL Server, LAG() is a window function that enables us to access a value from a previous row in the same result set, without the need to perform a self-join.
We specify the previous row as an offset from the current row. An offset of 1 means the previous row, an offset of 2 means two rows back, and so on.