Using a cursor, how to handle the error in SQL - sql-server

Question

I have multiple databases in which I am looking for a particular column called Countries. If the column exists then I check the space characters in the column. If I loop through a cursor, the DB which is not having a Countries column will throw an error. How can I handle this error?
Concern: the catch block is not handling, please help me how to resolve the issue.
Query as shown below,
CREATE PROCEDURE [dbo].[USP_SMSGeneric_CountrySpace] #DB VARCHAR(100)
As
BEGIN
SET NOCOUNT ON
DECLARE #StudyID varchar(max)
DECLARE #Databasename VARCHAR(max)
DECLARE #QUERY NVARCHAR(MAX)
DECLARE #Protocol varchar(max)
DECLARE #Servername varchar(max)
DECLARE #script VARCHAR(Max)
DECLARE #script1 VARCHAR(Max)
DECLARE #initscript NVARCHAR(Max)
DECLARE #Countries VARCHAR(Max)
DECLARE #Countryrelease VARCHAR(Max)
IF OBJECT_ID('TEMPDB..#OBJMISSING') IS NOT NULL DROP TABLE #OBJMISSING
CREATE TABLE #OBJMISSING (ERRID INT IDENTITY(1,1),ERRNUM BIGINT,ERRMSG VARCHAR(MAX),DBNAME VARCHAR(MAX))
SET #initscript='
DECLARE csrStudy CURSOR FOR
SELECT ProtocolName, DBName, studyid,DBServer AS Servername from SMSAPP.dbo.studymaster WITH (NOLOCK)
WHERE ClientName LIKE ''%NOVARTIS%'' AND studystatus IN (1,2) AND DBServer IN (''SQL002'' ,''SQL004'',''SQL005'')
'
EXEC sp_executesql #initscript
OPEN csrStudy
FETCH NEXT FROM csrStudy INTO #Protocol,#Databasename,#StudyID,#ServerName
WHILE ##FETCH_STATUS = 0
BEGIN
SET #DB = #Servername+'.'+#Databasename
SET #script = '
DECLARE #StrValue VARCHAR(max)
BEGIN TRY
IF EXISTS (
SELECT DISTINCT 1 FROM '+#DB+'.sys.columns c JOIN '+#DB+'.sys.Tables t ON c.Object_ID=t.Object_ID
WHERE c.Name = ''Countries’'' AND t.name =''tblMaterials'')
BEGIN
SELECT #StrValue = ISNULL(#StrValue + '','', '''') + Countries’ FROM (
SELECT DISTINCT (LEN(Countries’ + '','') - LEN(REPLACE(Countries’, '' '', '''') + '',''))CNT,Countries
FROM '+#DB+'.dbo.tblMaterials WITH (NOLOCK) )A WHERE CNT>0
END
END TRY
BEGIN CATCH
INSERT INTO #OBJMISSING VALUES
(ERROR_NUMBER(),ERROR_MESSAGE(),''+#Databasename+'')
END CATCH
IF #StrValue IS NOT NULL -- If any Duplicate values found, then raise an alert
BEGIN
SELECT '+#StudyID+' As StudyID,
''Countries field value Should not have space'' AS Actual ,
''Countries field value exists with space for String :'' + #StrValue AS Discrepancy INTO #tempOutput
I'm getting the following error:
The OLE DB provider "SQLNCLI10" for linked server "SQL001" does not
contain the table ""RAW."dbo"."tblMaterials"". The table either does
not exist or the current user does not have permissions on that table

Answer 1

You need a TRY CATCH outside the dynamic SQL.
The error message that is displayed is at parse time, before it even executes (for that EXEC statement). At this moment the engine validates that the tables and objects exist and if not then an error is returned. The execution never starts so it will never get to the CATCH section. This is why the TRY CATCH needs to be outside the dynamic SQL, because the whole dynamic SQL will get rejected after parsing.
The error message you are getting is coming from a query like the following:
EXEC('SELECT * FROM [SomeLinkedServer].DatabaseName.SchemaName.NonExistingTable')
Msg 7314, Level 16, State 1, Line 1 The OLE DB provider "SQLNCLI11"
for linked server "SomeLinkedServer" does not contain the table
""DatabaseName"."SchemaName"."NonExistingTable"". The table either does not exist or
the current user does not have permissions on that table.
If you can wrap this on a TRY CATCH, then the control flow will jump to the catch since the severity of the error is high enough:
BEGIN TRY
EXEC('SELECT * FROM [SomeLinkedServer].DatabaseName.SchemaName.NonExistingTable')
END TRY
BEGIN CATCH
SELECT 'This is the catch section'
END CATCH
Please note the difference against this following example, without dynamic SQL:
BEGIN TRY
SELECT 1 FROM [SomeLinkedServer].DatabaseName.SchemaName.NonExistingTable
END TRY
BEGIN CATCH
SELECT 1
END CATCH
Msg 208, Level 16, State 1, Line 3 Invalid object name
'DatabaseName.SchemaName.NonExistingTable'.
This is because the whole batch is being rejected after parsing, so it can't jump to a CATCH as it never started execution. When you use dynamic SQL, the parse, compile and execute of the dynamic portion happens at the EXEC point (and that is exactly why it's dynamic), delaying the error throw so it can be caught.
I can't supply the full fixed code because what you posted isn't complete. But you should be able to ignore errors if you follow this guideline:
DECLARE #Variable ...
DECLARE MyCursor CURSOR FOR ...
FETCH NEXT FROM MyCursor INTO #Variable
WHILE ##FETCH_STATUS = 0
BEGIN
BEGIN TRY
DECLARE #DynamicSQL VARCHAR(MAX) = ... -- The DynamicSQL may have another TRY CATCH inside
EXEC(#DynamicSQL)
END TRY
BEGIN CATCH
-- Do your catch operation here, you can leave this section empty if you want (not recommended)
END CATCH
FETCH NEXT FROM MyCursor INTO #Variable
END