title: Oracle SQL: Select Minimum and maximum from different rows
body: <p>I have a table which looks like this (max 2 rows per each Date-Item):</p>
  
  <pre>
      Date        Item Price
      -----------------------
      20140101    A     100
      20140101    A     200
      20140101    B     50
      20140101    B     70
      20140102    A     20
      20140102    A     40
      20140102    B     10
      20140102    B     60
  </pre>
  
  <p>How can I have the maximum and minimum prices for each Date-Item pair in one row, as shown below? </p>
  
  <p>There can be Date_Items with only one price (one row). For these pairs, I would like to have that price as Min_Price and NULL as Max_Price.</p>
  
  <pre>
      Date        Item Min_Price  Max_Price
      --------------------------------------
      20140101    A     100      200
      20140101    B     50       70
      20140102    A     20       40
      20140102    B     10       60
  </pre>