How to express equal to empty in Oracle

There are two ways to represent null values ​​in Oracle: NULL represents missing or unknown information, which is not equal to any value. The empty string ('') represents a text value without any characters, is not equal to NULL, and can be compared with other strings.

Representation of null values ​​in Oracle

There are two ways to represent null values ​​in Oracle: NULL and null characters string('').

NULL

• NULL is a special value that represents missing or unknown information.
• It cannot be equal to any other value (including itself).
• In SQL statements, NULL is usually used as a placeholder to indicate that no data exists.
• For example:

<code class="sql">SELECT * FROM table_name WHERE column_name IS NULL;</code>

Empty string

##The empty string ('') represents a text value in which there is no any character.
• It is essentially a string of length 0.
• Empty strings are not equal to NULL and can be compared with other strings.
• For example:

<code class="sql">SELECT * FROM table_name WHERE column_name = '';</code>

Distinguish between NULL and empty string

It is very important to distinguish between NULL and empty string because they are used in SQL statements The functions in are different:

NULL is used to represent missing or unknown information.
• The empty string is used to represent a value without characters.

Remember that NULL is not equal to all other values ​​(including itself), while the empty string can be compared with other strings.

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