Dynamic query based on datetime parameter - sql

Question

I have a SQL Server database with date representation name like below & each database contains table A (table A having column like id, datetime, value, value1 etc).
Jan2018
Feb2018
Mar2018 and so on..
My search condition is user selected date (eg. from 01-Jan-2018 to 01-Jun-2018) which I am passing to a stored procedure (max range 6 month). I want to generate dynamic query to get data from these database based on datetime passed.
How to achieve this functionality as I found difficult to implement.

Answer 1

Can you try this query
CREATE PROCEDURE Myproc #FromDate DATE,
#ToDate DATE
AS
BEGIN
DECLARE #SQL NVARCHAR(max)='',
#unionall VARCHAR(10)=''
WITH cte
AS (SELECT #FromDate dt,
1 mont
UNION ALL
SELECT Dateadd(month, 1, dt) dt,
mont + 1 mont
FROM cte
WHERE mont < Datediff(month, #FromDate, #ToDate)
)
SELECT #SQL += #unionall + '
select * from ['
+ LEFT (CONVERT(VARCHAR, Datename (month, dt )), 3)
+ CONVERT (VARCHAR, Year (dt))
+ '].[dbo].[tablename]',
#unionall = ' union all '
FROM cte
PRINT #SQL
EXECUTE( #SQL)
END

Answer 2

You should query sys.databases to find a database you need.
Then, as you can only use static declarations of databases, you should create a textual select statement and execute it.
I tried it on my dbs and it worked.
This is my code:
declare #date varchar(20) = '2018'
declare #dbName varchar(20)
declare #sSql varchar(200)
declare #sConditions varchar(20) = ''
Set #dbName = (SELECT name FROM master.sys.databases
where name like '%' + #date + '%')
print #dbName
Select #sSql = 'Select * From ' + #dbName + '.dbo.MyDB '
--+ ' Where ' + #sConditions
Execute (#sSql)
if you need to query all that fit year. do like this:
declare #date varchar(20) = 'a'
SELECT name Into #dbnames
FROM master.sys.databases
where name like '%' + #date + '%'
this brings a table of all sutable dbs. then query each one of them using loop. like cursor

Answer 3

Are you looking for
CREATE PROCEDURE MyProc
#FromDate DATE,
#ToDate DATE,
#Target SysName
AS
BEGIN
DECLARE #SQL NVARCHAR(MAX)= N'SELECT * FROM [' +
#Target +
'] WHERE [Dates] >= #FromDate AND [Dates] <= #ToDate';
EXECUTE sp_executesql #SQL,
N'#FromDate DATE, #ToDate DATE',
#FromDate,
#ToDate;
END
Demo
As I now understand what you are trying to do, you can
CREATE PROCEDURE ProcName
#FromDate DATE,
#ToDate DATE
AS
BEGIN
--Declare a variable to hold the Dynamic SQL
DECLARE #SQL NVARCHAR(MAX) = N'';
--Generate the databases names
WITH CTE AS
(
SELECT #FromDate D,
1 N
UNION ALL
SELECT DATEADD(Month, N, #FromDate),
N + 1
FROM CTE
WHERE N <= DATEDIFF(Month, #FromDate, #ToDate)
)
--Build the SELECT statement
SELECT #SQL = #SQL+
N'SELECT * FROM ['+
CONVERT(VARCHAR(3), D, 100)+
CAST(YEAR(D) AS VARCHAR(4))+
'].dbo.TableName UNION ALL ' --Or UNION as you want
FROM CTE;
--Remove the last UNION ALL
SET #SQL = LEFT(#SQL, LEN(#SQL) - 10); --If UNION then just -6
--Execute the statement
EXECUTE sp_executesql #SQL;
END