SQL Query Summary - mysql

Question

i would create a particular sql string.
I have this tables :
cities
-----------
city varchar not null primary key
etc
weeks
-----------
week varchar not null primary key
Insert_data
-----------
id int not null primary key
cityID varchar
week varchar
value1 int
etc
I would to bind asp.net gridview with this table structure:
+-----+-------+-------+-------+
| city| week1 | week2 | week3 |
+-----+-------+-------+-------+
| 1 | (y/n) | (y/n) | (y/n) |
| 2 | (y/n) | (y/n) | (y/n) |
| 3 | (y/n) | (y/n) | (y/n) |
| 4 | (y/n) | (y/n) | (y/n) |
| 5 | (y/n) | (y/n) | (y/n) |
+----+-------+-------+-------+
if there are records related to that week in insert_data the value will be Y.
It's possible to create a query string for this?

Answer 1

As always, when you need to create columns from rows with a "group by argument" (city), you can use the PIVOT operator.
http://technet.microsoft.com/en-us/library/ms177410(v=sql.105).aspx
Above only applies to MS-SQL, doesn't apply to MySQL.
Or you can do it the old-fashioned way
SELECT
cities.city
,SUM(CASE WHEN weeks.week = 1 THEN Insert_data.value1 ELSE 0 END) AS week1
,SUM(CASE WHEN weeks.week = 2 THEN Insert_data.value1 ELSE 0 END) AS week2
,SUM(CASE WHEN weeks.week = 3 THEN Insert_data.value1 ELSE 0 END) AS week3
,SUM(CASE WHEN weeks.week = 4 THEN Insert_data.value1 ELSE 0 END) AS week4
-- ,etc. for each week (select distinct week from insert_data order by week)
FROM Insert_data
left join cities
cities.city= Insert_data.cityID
left join weeks
on weeks.week = Insert_data.week
group by cities.city
Either way, you need to dynamically hardcode the weeks in your SQL string.
You would now need an additional condition for y and n, and then you can concat the values.
,'(' + CAST(SUM(CASE WHEN weeks.week = 1 AND value1 = 1 THEN 1 ELSE 0 END) as varchar(10))
+ '/'
CAST(SUM(CASE WHEN weeks.week = 1 AND value1 = 0 THEN 1 ELSE 0 END) as varchar(10))
+ ')'
AS week1
or if it's just y or no, then
,
CASE
WHEN SUM(CASE WHEN weeks.week = 1 THEN Insert_data.value1 ELSE 0 END) > 0
THEN 'y'
ELSE 'n'
END AS week1