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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
Wartość NULL definiuje atrybut lub logiczny wynik porównania jako nieokreślony, niezdefiniowany. Może występować w rekordach (elementach zbioru), w kolumnach, którym nie zostały określone wartości. NULL nie jest równy 0, ani też nie jest to wartość pusta w sensie pustego stringu ”.
14 maj 2021 · SQL Comparison Operators that Work with NULLs. 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.
20 cze 2024 · This tip will help you understand what NULL means in the context of the Microsoft Fabric data universe, which includes SQL Server. It will then show how these values can make queries act unexpectedly and how to best interact with NULL values to avoid problems.
3 gru 2009 · The expression "NULL = NULL" evaluates to NULL, but is actually invalid in SQL; yet ORDER BY treats NULLs as equal (whatever they precede or follow "regular" values is left to DBMS vendor). The expression "x IS NOT NULL" is not equal to "NOT (x IS NULL)", as is the case in 2VL.
12 wrz 2024 · To test for null values in a query, use IS NULL or IS NOT NULL in the WHERE clause. You can insert null values into a column by explicitly stating NULL in an INSERT or UPDATE statement, or by leaving a column out of an INSERT statement.
26 kwi 2023 · How to Use SQL Server Coalesce to Work with NULL Values; Join SQL Server Tables Where Columns Include NULL Values; SQL WHERE IS NOT NULL for SELECT, INSERT, UPDATE and DELETE; Some Tricky Situations When Working with SQL Server NULLs; How To Retrieve the Last Non-NULL Value in SQL Server; SQL Server NOT Equal Operators; SQL ORDER BY Clause
