Not equal to number ____oracle in Oracle

Today encountered an Oracle is not equal to the problem, and finally searched, and found the following information, to share with you about Oracle in the Not equal number:

In Oracle,

<>
!=
~=
^=

is not equal to the meaning of the number. can be used.

But it's weird. Yes, I want to take out a product that price is not 180000: (Price is of type number)

SELECT ID, name from product where Price<> 180000;

When executing this statement, Priceis NULL is not logged. That is, you can't get a commodity that price is null. Must use:

SELECT ID, name from product where price<> 180000 or price is null;

The same problem exists with the field of the string.

Keep in mind that NULL can only be judged by IS null or is not NULL, and that other operators and null operations are false.

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Test: SELECT * from test where name<> ' xn '. Only records with a name that are not empty can be detected. Get rid of name<> ' xn '. There is a problem with this type of wording.

Then use the InStr (name, ' xn ') = 0来 to judge if the name is not empty, the judgment is valid. If name is empty, the judgment goes wrong again. Forced to take InStr (name, ' xx '), ' xn ') = 0来 judgment, because even if the name is empty, and ' xx ' after the connection, it will not be empty.

So the final SQL statement is:

SELECT * FROM Test where InStr (concat (name, ' xx '), ' xn ') = 0来 query Name field is not equal to ' xn ' record.

       you can query for records that are not equal to ' xn ' in the Name field using SELECT * from Test where NVL (name, ' xx ') <> ' xn '