Is this possible with SQL Server - sql

Question

I have a table which has events and the day they occurred:
Table 'Events':
Name Day
-----------
A 1
B 2
A 2
B 3
I need output columns to be a date range based on query input with rows being which event happened on the day so:
Desired output:
Day-1 Day-2 Day-3
-----------------
A A -
- B B
If this is possible can anyone give me a sample query that could generate this output based on a date range. There are all sorts of I have no clue how to even approach this issues here like an unknown number of columns.

Answer 1

You can use conditional aggregation:
select max(case when day = 1 then name end) as day_1,
max(case when day = 2 then name end) as day_2,
max(case when day = 3 then name end) as day_3
from t
group by name;
Note: This returns NULL rather than -. I think NULL makes more sense.

Answer 2

Try this one...
Table Script and Sample data
CREATE TABLE [TableName](
[Name] [nvarchar](50) NULL,
[Day] [int] NULL
)
INSERT [TableName] ([Name], [Day]) VALUES (N'A', 1)
INSERT [TableName] ([Name], [Day]) VALUES (N'B', 2)
INSERT [TableName] ([Name], [Day]) VALUES (N'A', 2)
INSERT [TableName] ([Name], [Day]) VALUES (N'B', 3)
Query (dynamic PIVOT)
DECLARE #startDay AS INT;
DECLARE #endDay AS INT;
SET #startDay = 1;
SET #endDay = 3;
DECLARE #cols AS NVARCHAR(max) = Stuff((SELECT DISTINCT ',' + Quotename([day])
FROM TableName
WHERE [Day] >= #startDay AND [Day] <= #endDay
FOR xml path(''), type).value('.', 'NVARCHAR(MAX)'), 1, 1, '');
DECLARE #query AS NVARCHAR(max) = 'SELECT '+ #cols +'
FROM (SELECT *,
Dense_rank() OVER (ORDER BY NAME) AS dr
FROM TableName) sq
PIVOT(Max([name])
FOR [day] IN ('+ #cols +') ) pvt ';
EXECUTE(#query)
Output
+--------+---+--------+
| 1 | 2 | 3 |
+--------+---+--------+
| A | A | (null) |
| (null) | B | B |
+--------+---+--------+
Online Demo: http://www.sqlfiddle.com/#!18/c688b/8/0
If you also want to use custom column name, try this...
DECLARE #startDay AS INT;
DECLARE #endDay AS INT;
SET #startDay = 1;
SET #endDay = 3;
DECLARE #cols AS NVARCHAR(max) = Stuff((SELECT DISTINCT ',' + Quotename([day])
FROM TableName
WHERE [Day] >= #startDay AND [Day] <= #endDay
FOR xml path(''), type).value('.', 'NVARCHAR(MAX)'), 1, 1, '');
DECLARE #colNames AS NVARCHAR(max) = Stuff((SELECT DISTINCT ',' + Quotename([day]) + ' AS Days' + CONVERT(NVARCHAR(MAX), [day])
FROM TableName
WHERE [Day] >= #startDay AND [Day] <= #endDay
FOR xml path(''), type).value('.', 'NVARCHAR(MAX)'), 1, 1, '');
DECLARE #query AS NVARCHAR(max) = 'SELECT '+ #colNames +'
FROM (SELECT *,
Dense_rank() OVER (ORDER BY NAME) AS dr
FROM TableName) sq
PIVOT(Max([name])
FOR [day] IN ('+ #cols +') ) pvt ';
EXECUTE(#query)
Output
+-------+-------+-------+
| Days1 | Days2 | Days3 |
+-------+-------+-------+
| A | A | NULL |
| NULL | B | B |
+-------+-------+-------+
Online Demo: http://www.sqlfiddle.com/#!18/c688b/9/0