MySQL: fetching a null or an empty string -
 I know that a  NULL  value and an empty string ( "" ) value, but if I want to get a value using the keyword  or , then I can not find any results for  NULL  value 
is. I want to ask that the table looks like this:
  titles_and_tags + ---- + ---------- + ------ + | ID | Title | Tag | + ---- + ---------- + ------ + | 1 | Title 1 Faucet | 2 | Heading 2 | Tag 1 | | 3 | Title 3 Tag 2 | | 4 | Edit | Faucet | 5 | Roudata | Div | + ---- + ---------- + ------ +   The use of my query looks like this:
Select * by selecting the name "and" Tag "=" Tag 1 "or" Tag ") * Select * by name 
So I get one here Do the rows (id: 1,2), but this result is 0 rows. What have I done?
Edit
Sorry, I Forgotten that my main problem is:
  select 'Titles_and_tags` from WHERE' title 'such as "title%" and "tag` =" tag1 " '%' Like 'tag'   then it is more like a closed subject, sorry
Try
  heading * and tags with the title 'WHERE' *    You have a wildcard % < Except "code" and left your  "" "heading"% "and (` tag` = "tag1" or "tags" such as , and you enter  or  should be included in the clause for clarity and clearly to ensure that it is fair with your intention Have been committed, group together logic together. 
  Edit:  Your edit will match the  tag '%' such as  all the rows that do not have the tag  null . A  null  value is incorrect with  any   or  is not  other than   I'm not sure that you What are you trying to do with the last question, but I suspect that the question you asked for was originally what you really want. 
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