title: SQL Avoid summing rows multiple times based on LIKE expression
body: <p>I have a table with bank transactions with columns id, tDate, description, cashOut, cashIn. I want to see how I spend my money, specifically at Amazon and a shop called Mazo, so I want a result like this:</p>
  
  <pre><code>Month   Amazon   Mazo   Total
  1       100      200    300
  </code></pre>
  
  <p>I attempted this:</p>
  
  <pre><code>SELECT
      MONTH(tDate) AS Month,
      SUM(IF(description LIKE '%amazon%',cashOut,0)) AS Amazon,
      SUM(IF(description LIKE '%mazo%',cashOut,0)) AS Mazo,
      SUM(cashOut) AS Total
  FROM `transactions` 
  GROUP BY Month
  </code></pre>
  
  <p>However, I got the following:</p>
  
  <pre><code>Month   Amazon   Mazo   Total
  1       100      300    300
  </code></pre>
  
  <p>The problem with this SQL query is that the sum of "mazo"-transactions is wrong, because it also adds up the "amazon" transactions.</p>
  
  <p>I want the selection of the transactions to sum to be mutually exclusive or something like that, so that each transaction is part of only one of the SUMs above (without resorting to PHP or similar). (My tables contain much more data than this, and I have lots of search criteria, so it doesn't suffice to use '% mazo %' as search word. I need a general solution to the problem.)</p>
  
  <p>Does anybody have a suggestion?</p>
  
  <p><em>Details of the table and its data:</em></p>
  
  <pre><code>CREATE TABLE `transactions` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `tDate` date NOT NULL,
  `description` varchar(200) NOT NULL,
  `cashOut` decimal(10,0) NOT NULL,
  `cashIn` decimal(10,0) NOT NULL,
  PRIMARY KEY (`id`)
  ) ENGINE=InnoDB 
  
  INSERT INTO `transactions` (`id`, `tDate`, `description`, `cashOut`, `cashIn`) VALUES
  (1, '2010-01-05', 'amazon', '100', '0'),
  (4, '2010-01-15', 'mazo', '200', '0');
  </code></pre>