Why does NULL = NULL evaluate to false in SQL server
Dec 4, 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 …
What is the difference between "is not null" and "!= null"?
Sep 21, 2021 · The only difference (besides the syntax) is, that the compiler guarantees that no user-overloaded operator is called when using is not null instead of != null (or is null instead of == null). …
What's the difference between " = null" and " IS NULL"?
May 1, 2010 · Understanding the difference between “IS NULL” and “= NULL” When a variable is created in SQL with the declare statement it is created with no data and stored in the variable table …
sql - Not equal <> != operator on NULL - Stack Overflow
Apr 14, 2011 · 135 NULL has no value, and so cannot be compared using the scalar value operators. In other words, no value can ever be equal to (or not equal to) NULL because NULL has no value. …
How to send NULL in HTTP query string? - Stack Overflow
So if you don't need to support the difference between empty and null/absent string you may also consider the empty parameter as null. If instead you want to recreate point 4. of JSON {"param":null} …
Best way to check for null values in Java? - Stack Overflow
The null check will be at least a thousand times faster (probably many thousands). For the path of execution to get into the catch block an exception has to have been raised which means generating …
How can I check for an undefined or null variable in JavaScript?
The title of this bug says "check for undefined or null", but the question itself checks for undeclared or null.
What exactly is meant by "dereferencing a NULL pointer"?
In other words, a null pointer is a pointer of any type pointing at a well-defined "nowhere". Any pointer can turn into a null pointer when it is assigned a null pointer constant. The standard mentions 0 and …
What are the differences between Null, Zero and Blank in SQL?
Sep 6, 2017 · Comparing NULL with anything yields a NULL. NULL is part of trinary logic: TRUE, FALSE, and NULL. -- These are all NULL. select NULL > -1, NULL < -1, NULL = NULL, NULL = 0; …
How do I create a unique constraint that also allows nulls?
Apr 20, 2009 · I want to have a unique constraint on a column which I am going to populate with GUIDs. However, my data contains null values for this columns. How do I create the constraint that allows …