where子句中的列'book-category'含糊不清

Question

I'm facing a problem in this sql query

SELECT * FROM `book` join `journal`  
 WHERE  `book-category` LIKE '$maincat2' 
   AND `book-category` LIKE '$subcat2'  
   AND `book-category` LIKE '$country2' 
   AND `book-category` LIKE '$procat2' 

the table strukture are same book=journal

What is the reason?

Answer 1

both book and journal have a book-category column, so MySQL doesn't know which one to apply the condition on. You can solve this by fully referencing them with a table name. Eg:

SELECT * FROM `book` join `journal`  
 WHERE  `book`.`book-category` LIKE '$maincat2' 
   AND  `book`.`book-category` LIKE '$subcat2'  
   AND  `book`.`book-category` LIKE '$country2' 
   AND  `book`.`book-category` LIKE '$procat2' 

Answer 2

Maybe it's me but your query as it is doesn't make much sense to me.

Probably you wanted something like this (using UNION instead of JOIN ) and if, as you said, table schemas actually are the same for book and journal

SELECT 'book' type, b.* 
  FROM book b
 WHERE book-category LIKE '$maincat2' 
   AND book-category LIKE '$subcat2'  
   AND book-category LIKE '$country2' 
   AND book-category LIKE '$procat2' 
UNION ALL
SELECT 'journal', j.* 
  FROM journal j
 WHERE book-category LIKE '$maincat2' 
   AND book-category LIKE '$subcat2'  
   AND book-category LIKE '$country2' 
   AND book-category LIKE '$procat2'