title: How to remove NULL from case when and then output Oracle SQL Developer
body: <p>Oracle SQL Developer noob here. I am trying to create a quarterly sales analysis based on warehouse names and output the Quarterly sales as Q1, Q2 etc. Using Drill down query concepts.</p>
  <p>I am unsure if what I am doing is in any way related to a Drill Down concept but this is one of my many attempts. I am hoping for a way to remove the null value outputs to be left with proper data.</p>
  <p>It is in the hopes that with the removal of the null data, all the outputs related to specific warehouse names will also all output to 1 line. Leaving me with Warehouse_Name(1), Q1 Data, Q2 Data, etc</p>
  <p>I am currently using two tables for this query which are
  Warehouse: Warehouse_id, warehouse_name and quantity_sold
  Time_Period: Date_id, Full_date, Days, Month_short and year.</p>
  <p>My Code is as follows:</p>
  <pre><code>SELECT TO_CHAR(Full_date, 'Q') AS MY_QTR, 
      Sum(Quantity_sold) AS HOW_MANY_SOLD_PER_QTR
  FROM warehouse, Time_Period 
  GROUP BY TO_CHAR(Full_date, 'Q')
  ORDER BY 1;
  Select warehouse_Name,
  case 
  when TO_CHAR(Full_date, 'Q') = 1
  then Sum(Quantity_sold) 
  End as Q1_2019,
  case 
  when TO_CHAR(Full_date, 'Q') = 2
  then Sum(Quantity_sold)
  End as Q2_2019,
  case 
  when TO_CHAR(Full_date, 'Q') = 3
  then Sum(Quantity_sold)
  End as Q3_2019,
  case 
  when TO_CHAR(Full_date, 'Q') = 4
  then Sum(Quantity_sold)
  End as Q4_2019
  FROM warehouse w1, Time_Period t1
  where Q1_2019 IS NOT NULL
  GROUP BY warehouse_Name,TO_CHAR(Full_date, 'Q')
  ORDER BY 1;
  </code></pre>
  <p>Which provides me with an output of</p>
  <pre><code>Waarehouse_Name   Q1   Q2   Q3   Q4
  --------------- ---- ---- ---- ----
  Henderson        990 Null Null Null    
  Henderson       Null 1001 Null Null
  Henderson       Null Null 1012 Null
  Henderson       Null Null Null 1012
  </code></pre>