Value not Store in Dynamic SQL - tsql

Question

I've different different tables to categorically store data and a log table where all the transactions log are recorded
e.g. 1) VoucherNO, Add, ...
2) VoucherNO, Delete, ..
After I backup the database and restore in another server for my Reporting Purpose. That time I want to ensure all the log data and transaction are available in TestDB if not then I remove log from 'AUD_USER_ACTIVITY'.
To find the transaction exist or not, I create a dynamic sql select statement and check whether record is exist or not.
Basis on #RecExist Value I do the action like if records is not available in TestDB the log will be remove, if record exist immediately break this loop and going for next procedure
But #RecExist variable is not updating in Dynamic SQL Execution. Please guide me
declare #MvDocNo varchar(50)
DECLARE #SCtr as DECIMAL(10,0)
declare #LocationCode varchar(4)
declare #UName Nvarchar(40)
declare #toe varchar(30)
declare #QryTxt as nvarchar(MAX);
Declare #RecExist as INT =0;
SET #RecExist=0
WHILE #RecExist=0
BEGIN
select top 1 #MvDocNo=DOCNO, #SCtr=SrlNo,#LocationCode =DMLTYPE,#UName=TABLENAME
FROM R_AUDDB..AUD_USER_ACTIVITY
WHERE DBNAME='TestDB' and DMLTYPE not in ('AD','D','PD') ORDER BY SRLNO DESC;
select top 1 #toe=docno from TestDB..M_TYPEOFENTRY where TBLNAME=#UName;
set #QryTxt='Select #RecExist=1 From R_TestDB..'+#UName+ ' Where '+#toe+'='''+#MvDocNo+''''
exec (#QryTxt)
IF #RecExist=0
BEGIN
DELETE R_AUDDB..AUD_USER_ACTIVITY WHERE SRLNO=#SCtr
END
END

Answer 1

The following code sample demonstrates how to check for a row in a table with a specific column and value using dynamic SQL. You ought to be able to change the values of the first three variables to reference a table and column in your database for testing.
Note that SQL injection is still possible: there is no validation of the table or column names.
-- Define the table to check and the target column name and value.
declare #TableName as SysName = 'Things';
declare #ColumnName as SysName = 'ThingName';
declare #TestValue as NVarChar(32) = 'Beth';
-- Create a SQL statement to check for a row in the target table with the specified column name and value.
declare #SQL as NVarChar(1024);
declare #Result as Bit;
-- Note that only object names are substituted into the statement at this point and QuoteName() is used to reduce problems.
set #SQL = N'select #iResult = case when exists ( select 42 from dbo.' + QuoteName( #TableName ) +
N' where ' + QuoteName( #ColumnName ) + N' = #iTestValue ) then 1 else 0 end;'
select #SQL as SQL;
-- Execute the SQL statement.
-- Note that parameters are used for all values, i.e. the target value and return value.
execute sp_executesql #stmt = #SQL,
#params = N'#iTestValue NVarChar(32), #iResult Bit output',
#iTestValue = #TestValue, #iResult = #Result output
-- Display the result.
select #Result as Result;