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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 ”.
The SQL Server ISNULL() function lets you return an alternative value when an expression is NULL: SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0)) FROM Products;
24 maj 2022 · Example 1: Use COALESCE () to Replace NULL with a Label. Example 2: Use COALESCE () When Concatenating NULL and Strings. Example 3: Use COALESCE () with Multiple Arguments. Example 4: Use COALESCE () to Replace NULL with a Calculated Value. Example 5: Use COALESCE () with the ROLLUP Clause.
19 maj 2021 · What is a SQL NULL value? In terms of the relational database model, a NULL value indicates an unknown value. If we widen this theoretical explanation, the NULL value points to an unknown value but this unknown value does not equivalent to a zero value or a field that contains spaces.
When off, any query that compares a value with a null returns a null value. QUOTED IDENTIFIER ON/OFF: This options specifies the setting for usage of double quotation.
This tutorial introduces you to the SQL COALESCE function and shows you some practical examples of using the COALESCE function to handle NULL effectively.
