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(Databases-MySQL) NULL Value 본문
< Null Value in MySQL >
What is a NULL Value?
: NULL value is a filed with no value. NULL is not value, it's just a place holder
** Therefore, we can't compare between NULL values!
Null is unknown, so they can't be same ! null != null
Can we test for NULL?
: Yes, it's possible to test for using IS NULL & IS NOT NULL
NULL Value with Groung and Aggregating
: Nulls are counted when grouping, but ignored when aggregating!
Reference :
https://www.tutorialspoint.com/sql/sql-null-values.html
SQL - NULL Values
The SQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank.
www.tutorialspoint.com
https://www.w3schools.com/SQl/sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
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