The SQL EXISTS predicate is used to specify a test for a non-empty set. It returns TRUE or FALSE, depending on the outcome of the test.
When we incorporate the EXISTS predicate operator into our SQL queries, we specify a subquery to test for the existence of rows. If there are any rows, then the subquery is TRUE. If there are no rows, then the subquery is FALSE.
If you’re getting an error that reads “The function ‘FIRST_VALUE’ must have an OVER clause” in SQL Server, it’s probably because you’re calling the FIRST_VALUE() function without an OVER clause.
The FIRST_VALUE() 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 FIRST_VALUE() function.
When using the APPROX_PERCENTILE_DISC() function in SQL Server, you may get an error that reads “The function ‘APPROX_PERCENTILE_DISC’ must have a WITHIN GROUP clause“. If you get this error, it’s because you omitted the WITHIN GROUP clause when using the APPROX_PERCENTILE_DISC() function.
To fix this issue, make sure you include the WITHIN GROUP clause whenever you use the APPROX_PERCENTILE_DISC() function.
SQL Server 2022 introduced the IS [NOT] DISTINCT FROM predicate that compares the equality of two expressions and guarantees a true or false result, even if one or both operands are NULL.
Normally if we compare two NULL values, they will always be different (although this will depend on your ANSI_NULLS setting – setting ANSI_NULLS to OFF will result in NULLs being treated as equal). The IS [NOT] DISTINCT FROM predicate enables us to compare NULLs as though they’re equal, even when our ANSI_NULLS setting is set to ON.
If you’re using SQL Server’s GENERATE_SERIES() function/relational operator and you’re getting an empty result set, then it could be due to one of the following reasons.
In SQL, we can use the CREATE TABLE IF NOT EXISTS statement to create a table only if it doesn’t exist. The benefit of doing this is that we won’t get an error if there’s already a table with the same name.
But SQL Server doesn’t support this syntax – at least not in the current version of SQL Server at the time of writing (SQL Server 2022) .
So with SQL Server, we need to do a bit of extra work.
Continue readingIf you’re getting SQL Server error 4199 that reads “Argument value 0 is invalid for argument 3 of generate_series function“, it’s probably because you’re passing zero as the third argument to the GENERATE_SERIES() function.
The GENERATE_SERIES() function accepts an optional third argument, but this argument can’t be zero.
To fix this error, either pass a non-zero expression as the third argument, or omit the argument altogether (in order to use the default step of 1).
Continue readingSQL Server’s GENERATE_SERIES() function returns a series of numbers within a given interval. But just because it returns numbers, doesn’t mean we can’t leverage its functionality in order to generate a series of time values.
If you need to create a series of time values with evenly spaced intervals between a start and end point, maybe the following technique can help.
Continue readingFrom SQL Server 2022 we can use the JSON_PATH_EXISTS() function to test whether a specified SQL/JSON path exists in the input JSON string.
It’s similar to the JSON_CONTAINS_PATH() function that’s available in MySQL and MariaDB.
If you’re getting SQL Server error 10751 that reads “The ORDER BY in WITHIN GROUP clause of ‘APPROX_PERCENTILE_CONT’ function must have exactly one expression” it’s probably because you’re using too many ORDER BY expressions with the APPROX_PERCENTILE_CONT() function.
The APPROX_PERCENTILE_CONT() function requires the WITHIN GROUP clause, and that clause requires an ORDER BY sub-clause. However, that ORDER BY sub-clause requires exactly one expression – no more, no less. So, you can’t pass multiple expressions, and you can’t pass zero expressions. It must be exactly one expression.
To fix this issue, be sure to have just one ORDER BY expression in the WITHIN GROUP clause when using the APPROX_PERCENTILE_CONT() function.