How to select this in mysql ?

Question

the field value equal to zero OR it is NULL ?

Answer 1

SELECT * FROM table
WHERE field = 0 OR field IS NULL

Answer 2

SELECT * FROM [tablename] WHERE [fieldname] = 0 OR [fieldname] IS NULL

Answer 3

There is handy function called ISNULL which allows you to return a different value if it is. You can use it like:

SELECT ISNULL(fieldName, -999)
FROM _table

Also, for your main question:

SELECT * FROM _table
  WHERE field IS NULL OR field = 0