Заметка про NULL / Хабрахабр
Даже выражение NULL != NULL не будет истинным, ведь нельзя однозначно сравнить одну неизвестность с другой.
SQL is null and = null - Stack Overflow
Possible Duplicate: what is “=null” and “ IS NULL” Is there any difference between IS NULL and
sql - Counting null and non-null values in a single... - Stack Overflow
select sum(case when a is null then 1 else 0 end) count_nulls , count(a) count_not_nulls from us
LEFT JOIN / IS NULL vs. NOT IN vs. NOT EXISTS: nullable columns
SELECT NULL. FROM inner i. WHERE i.value = o.value ). When inner.value is marked as NOT NULL, all these queries are semantically equivalent and with proper indexing have similarly optimized execution plans in MySQL.
The Option type | F# for fun and profit | F# and null
Option vs. Null vs. Nullable. The option type often causes confusion to people who are used to dealing with nulls and nullables in C# and other languages.
ORACLE-BASE - NULL-Related Functions
Remember, comparisons against null always result in null, so queries can't use regular comparison operators like "=" or "!=". SQL> SELECT * FROM null_test_tab WHERE col1 = NULL ORDER BY id; no rows selected.
SQL NULL Values - IS NULL and IS NOT NULL
A field with a NULL value is one that has been left blank during record creation! How to Test for NULL Values? It is not possible to test for NULL values with comparison operators, such as =, <, or <>. We will have to use the IS NULL and IS NOT NULL operators instead.
C# Null Coalescing and Null Conditional Operators - Dot Net Perls
It simplifies null tests.","Null conditional."," Similar to the coalescing operator, the null conditional operator tests for null before accessing a member of an instance.","First example."," The null coalescing operator is useful inside properties.
How to replace NULL value by 0 in the Dynamic Pivot... | SqlHints.com
In this article let us understand replacing NULL values in the PIVOT result with an example.