What’s the difference between ” = null” and ” IS NULL”?

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In a WHERE clause, column=null will never be true, it is not valid to use null this way, you need to say column IS NULL or column IS NOT NULL. This speaks to the special nature of NULL, it is not a value to check for equality of, it is an unknown value, so you need to use the IS or IS NOT syntax.

You may assign something the NULL value using the = equal. For example: UPDATE TableX SET Column=NULL...

links:
Wikipedia NUll (SQL)
w3schools SQL NULL Values
SQL Tutorial, see IS NULL Operator section

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