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.
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.
Continue readingIf 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.
If you’re using SQL Server’s APPROX_PERCENTILE_DISC() function, and you’re getting error 10751 that reads “The ORDER BY in WITHIN GROUP clause of ‘APPROX_PERCENTILE_DISC’ function must have exactly one expression“, it’s probably because you’re passing too many ORDER BY expressions.
The APPROX_PERCENTILE_DISC() function accepts just one ORDER BY expression in its WITHIN GROUP clause.
To fix, be sure to use just one ORDER BY expression in the WITHIN GROUP clause when using the APPROX_PERCENTILE_DISC() function.
The SQL DISTINCT clause allows us to remove redundant duplicate rows from our query results. For example if two rows contain the same values, then only one of them is returned.
But how does DISTINCT handle NULL values?
Let’s find out.
Continue readingIf you’re getting an error message that reads “The function ‘PERCENT_RANK’ must have an OVER clause with ORDER BY” in SQL Server, it’s probably because you’ve omitted the ORDER BY clause from the OVER clause when using the PERCENT_RANK() function.
The PERCENT_RANK() 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.
If you’re getting an error in SQL Server that reads “The least function requires 1 to 254 arguments“, it’s probably because you’re either passing too few or too many arguments to the LEAST() function.
As the error message states, the LEAST() function requires at least 1 argument, and no more than 254 arguments.
To fix this issue, be sure to pass at least 1 argument, and no more than 254 arguments when using the LEAST() function.
In statistics, the mode is the most commonly occurring value in a data set. When using SQL databases, we can easily run a SQL query to find out the mode of a given column.
Below are several options we can use to calculate the mode in SQL.
Continue readingSuppose you’re trying to query column, but you need to set a minimum value to be returned, even if the column contains values that are less than that minimum. For example, you want a minimum value of 50 to be returned, even if the column contains values that are less than 50.
We can use the GREATEST() function to build such a query.
Most major RDBMSs support the DISTINCT clause, which allows us to get unique – or “distinct” – rows from our SQL queries. But PostgreSQL’s implementation of this clause has an extra option that most other RDBMSs don’t include.
PostgreSQL allows us to include the ON() option when using DISTINCT. This enables us to specify exactly which columns should be evaluated by the DISTINCT modifier, while simultaneously allowing us to return columns that aren’t evaluated.