title: Count occurrences of each value for every specific id
body: <p>I have a customer table like this:</p>
  
  <pre><code>trans-id | cust-id | trans-type | amount
  ----------------------------------------
     t1    |   c1    |    buy     |  700
     t2    |   c2    |    sell    |  200
     t3    |   c1    |    sell    |  400
     t4    |   c3    |    buy     |  900
     t5    |   c2    |    sell    |  100
  </code></pre>
  
  <p>I am trying to group up each of this customer with each of their type and amount. Below is the expected table that I want to get.</p>
  
  <pre><code>cust-id | num_of_trans | num_of_buy | num-of-sell | total_amount | total_buy | total_sell|
  ------------------------------------------------------------------------------------------
     c1   |      2       |     1      |      1      |     1100     |    700    |    400
     c2   |      2       |     0      |      2      |     300      |    0      |    300
     c3   |      1       |     1      |      0      |     900      |    900    |    0
  </code></pre>
  
  <p>I already try to use 'group by', but i can only get num_of_trans and total_amount. I have no idea how to split them as buy and sell. Anyone can help me? Thanks in advance.</p>