title: left join two tables on a non-unique column in right table
body: <p>I have two tables in sql server and i wanna select and join some data from these table.the first tables have some customer like:</p>
  
  <pre><code>---------------
  customer   id   
  Dave       1    
  Tom        2     
  ---------------
  </code></pre>
  
  <p>and second table i table of purchases that includes list of last purchases with cost and which customer bought that Product:</p>
  
  <pre><code>------------------
  product    date       customer id
  PC         1-1-2000   1
  phone      2-3-2000   2
  laptop     3-1-2000   1
  ------------------
  </code></pre>
  
  <p>i wanna select first table (customers info) with last date of their purchases!
  i tried left join but that doesn't give me last purchases becuase customer id is not unique in second table! how can i do this function with SQL server query? Regards</p>