Group by Week and then by Month

Question

Hello Forum Members,
Can you please help me on this:
City      Demand Demand_Date
Seattle    20     06/04/2014
Seattle    10     06/07/2014
Seattle    30     06/16/2014
Seattle    20     07/04/2014
Austin    10     06/07/2014
Austin    30     06/16/2014  
City       Demand           Demand_Week      Demand_by__Month  Demand_Month
Seattle     30              06/07/2014
Seattle     30              06/21/2014         60               
06/2014
Seattle     20              07/05/2014         20
Austin      10              06/07/2014
Austin      30              06/21/2014         40               
07/2014
Best,
Sqlquery9

Answer 1

Please post DDL, so that people do not have to guess what the keys, constraints, Declarative Referential Integrity, data types, etc. in your schema are. Now we have to guess because you are rude. 
Learn how to follow ISO-11179 data element naming conventions and formatting rules. Have no idea what this is. Temporal data should use ISO-8601 formats. You failed! 
Code should be in Standard SQL as much as possible and not local dialect. You did not even try! Are you always this rude to people that you want to do your job for you? 
This is minimal polite behavior on SQL forums. Here is my guess at cleaning up your mess. 
CREATE TABLE Cocaine_Demand
(city_name VARCHAR(15) NOT NULL,
 demand_date DATE DEFAULT CURRENT_TIMESTAMP NOT NULL,
 PRIMARY KEY (city_name, demand_date),
 demand_cnt INTEGER NOT NULL);
INSERT INTO Cocaine_Demand
VALUES
('Seattle', '2014-06-04', 20),
('Seattle', '2014-06-07', 10),
('Seattle', '2014-06-16', 30),
('Seattle', '2014-07-04', 20),
('Austin', '2014-06-07', 10),
('Austin', '2014-06-16', 30); 
Report Period Table
Since SQL is a database language, we prefer to do look ups and not calculations. They can be optimized while temporal math messes up optimization. A useful idiom is a report period calendar that everyone uses so there is no way to get disagreements in the DML.
The report period table gives a name to a range of dates that is common to the entire enterprise. 
CREATE TABLE Something_Report_Periods
(something_report_name CHAR(10) NOT NULL PRIMARY KEY
   CHECK (something_report_name LIKE <pattern>),
 something_report_start_date DATE NOT NULL,
 something_report_end_date DATE NOT NULL,
  CONSTRAINT date_ordering
    CHECK (something_report_start_date <= something_report_end_date),
etc);
These report periods can overlap or have gaps. I like the MySQL convention of using double zeroes for months and years, That is 'yyyy-mm-00' for a month within a year and 'yyyy-00-00' for the whole year. The advantages are that it will sort with the ISO-8601
data format required by Standard SQL and it is language independent. The pattern for validation is '[12][0-9][0-9][0-9]-00-00' and '[12][0-9][0-9][0-9]-[01][0-9]-00'
Weeks within Year: 
I would build a calendar table with a ISO-8601 week-within-year format column in addition to the usual Common Era date. This format is 'yyyyWww-d' where yyyy is the year, W is a separator token, ww is (01-53) week number and d is (1-7) day of the week.
You input any calendar date, find the week-within-year column and return the dates that match on a LIKE predicate.
WHERE sale_day LIKE '2012W26-[67]'
There are several websites with calendars you can cut & paste, but you can start your search with: http://www.calendar-365.com/week-number.html 
Try to write this yourself. If you were too lazy to post DDL or DML, why should we do it for you? 
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