One day has a colleague asked me how to find a word value null in a table and replaced it to another value.
Start me, I feel that the WHERE field = NULL should be available.
But the result is no error, but nothing is displayed.
Later, try:
SELECT * FROM table name where len (field) = 0 results still have no display.
Inadvertently, use the Select * from the name of WHERE field is null is right.
It seems that a lot of knowledge is to try more. Ha ha.
