How to determine whether data is empty in oracle

In Oracle, you can use the is keyword to determine whether the data is empty. Because null is regarded as a special symbol in SQL, the equal sign cannot be used. The syntax is "select * from table where column is null" .

The operating environment of this tutorial: Windows 10 system, Oracle 11g version, Dell G3 computer.

How does oracle determine whether the data is empty

oracle determines whether a field is empty

For example

insert into table a (a1,b1)values("a1",'');

In this case, because the table stores '', there is actually no content. To query this field, you cannot directly use

select *
from a
where b1='';

The equal sign cannot be used to judge non-empty in sql, because null is in sql are regarded as special symbols and must use the keywords is and not

should be used like this:

select * from A where b1 is null

or:

select * from A where b1 is not null

Recommended tutorial: "Oracle Tutorial》

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