Judgment of SQL null value

When the table is created , You can specify whether a column can contain no values , If there is no value in a column , Then it is called null NULL.NULL A special value , Represents a missing value or an inapplicable condition , Represents unknown data .NULL And fields contain 0、 Empty strings or just contain Spaces differently .

Yes NULL Value to perform more conventional operations , The result always returns unknown , So we need to use special operators ( Line drawing part IS [NOT] NULL).

SELECT column1,

       column2,

       ...

  FROM table

WHERE column IS [NOT] NULL

label ：MySQL