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9 paź 2014 · You can get duplicate NULLs in a SQL Server index by adding a WHERE clause in a filtered index (e.g. create unique index UK_MyTable on MyTable (Column) where Column is not null): msdn.microsoft.com/en-us/library/cc280372.aspx
Wynik porównania dwóch wartości NULL to także wartość nieznana. Nie jest ani większa, ani równa. Podobnie, jeśli byśmy chcieli porównać wartość znaną, z czymś czego nie znamy – wynik zawszę będzie UNKNOWN. Znajomość NULL skutkuje w wielu miejscach związanych z pisaniem zapytań.
You can change 'NULL' to something like 'All Values' if it makes more sense to do so. It should be noted that with two arguments, ISNULL works the same as COALESCE, which you could use if you have a few values to test (i.e.-COALESCE(@IN_MY_FIELD1, @OtherVal, 'NULL')).
14 maj 2021 · To handle NULLs correctly, SQL provides two special comparison operators: IS NULL and IS NOT NULL. They return only true or false and are the best practice for incorporating NULL values into your queries.
27 kwi 2017 · We've already covered how to use the GROUP BY clause and some aggregation functions like SUM (), AVG (), MAX (), MIN (), COUNT (). In this article, we will explain how the GROUP BY clause works when NULL values are involved. We will also explain about using NULL s with the ORDER BY clause.
19 maj 2021 · Handling SQL NULL values with Functions. As we stated earlier, SQL Server offers some functions that help to handle NULL values. ISNULL (): The ISNULL () function takes two parameters and it enables us to replace NULL values with a specified value. 1. ISNULL (expression,replacement)
Instead, you need to use the IS NULL or IS NOT NULL operator to check whether a value is null. For example, if you want to compare two values, column1 and column2, and column2 may be null, you can use the following SQL statement: SELECT * FROM your_table.
