update with dynamic SQL [duplicate] - sql

Question

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Update using SQL cursor SQL server [closed]
Closed 2 years ago.
I will explain my question, I use the AdventureWorksDW2012 database to demonstrate my purpose. I want to update the table based on the max date in this table where CurrencyID = 'CNY'
but I get the error Conversion failed when converting date and/or time from character string. I know the error because I use dynamic SQL statement but I should use it with cursor ..any help regarding this issue
here is my code
SET NOCOUNT ON
DECLARE
#AverageRate float
,#CurrencyID NVARCHAR(50)
,#CurrencyDate DATE
,#EndOfDayRate float
,#CurrencyKey float
,#DateKey float
,#MaxDate nvarchar(max)
Declare update_cursor
CURSOR
FOR
(select DISTINCT AverageRate
,CurrencyID
,CurrencyDate
,EndOfDayRate
,CurrencyKey
,DateKey from dbo.NewFactCurrencyRate1 );
OPEN update_cursor
FETCH NEXT FROM update_cursor INTO
#AverageRate
,#CurrencyID
,#CurrencyDate
,#EndOfDayRate
,#CurrencyKey
,#DateKey
WHILE ( ##FETCH_STATUS = 0)
BEGIN
if #CurrencyID = 'CNY'
begin
set #MaxDate = 'select max(CurrencyDate) from dbo.NewFactCurrencyRate1 '
EXEC (#MaxDate)
end
update dbo.NewFactCurrencyRate1
set CurrencyDate = #MaxDate
where CurrencyID = 'CNY'
FETCH NEXT FROM update_cursor INTO
#AverageRate
,#CurrencyID
,#CurrencyDate
,#EndOfDayRate
,#CurrencyKey
,#DateKey
END
CLOSE update_cursor
DEALLOCATE update_cursor

Answer 1

So far what I could understand from mobile view is you declared #maxdate as nvarchar but trying to store and update date field with it. Please use date data type.
#MaxDate date

Answer 2

You are attempting to "double use" the #MaxDate string. In one place you use it to hold the SQL you are trying to run, and in another place you are trying (but failing to) make it hold what should be the output of executing that SQL.
I would declare these as two variables:
#DynamicSQL nvarchar(max)
#MaxDate date
Then replace:
set #MaxDate = 'select max(CurrencyDate) from dbo.NewFactCurrencyRate1 '
EXEC (#MaxDate)
With
set #DynamicSQL = 'SET #MaxDate = (select max(CurrencyDate)
from dbo.NewFactCurrencyRate1)'
EXEC (#DynamicSQL)