How to rollback or commit a transaction in SQL Server

In my stored procedure, I have three insert statements.

On duplicate key value insertion first two queries generate the error

Violation of PRIMARY KEY constraint

and third query runs as usual.

Now I want that if any query generates any exception, everything should get rolled back.

If there isn't any exception generate by any query, it should get committed.

declare @QuantitySelected as char
    set @QuantitySelected = 2

    declare @sqlHeader as varchar(1000)
    declare @sqlTotals as varchar(1000)
    declare @sqlLine as varchar(1000)

    select @sqlHeader = 'Insert into tblKP_EstimateHeader '
    select @sqlHeader = @sqlHeader + '(CompanyID,CompanyName,ProjectName,EstimateID,EstimateHeader,QuoteDate,ValidUntil,RFQNum,Revision,Contact,Status,NumConfigurations) '
    select @sqlHeader = @sqlHeader + ' select CompanyID,CompanyName,ProjectName,EstimateID,EstimateHeader,QuoteDate,ValidUntil,RFQNum,Revision,Contact,Status,NumConfigurations '
    select @sqlHeader = @sqlHeader +  'from V_EW_Estimate_Header where EstimateID = 2203'



    select @sqlTotals = 'Insert into tblKP_Estimate_Configuration_Totals '
    select @sqlTotals = @sqlTotals + '(ConfigRecId,RecId,SellQty,ConfigNum,ConfigDesc,SortOrder,OptionsInMainPrice,MarkupPctQty,'
    select @sqlTotals = @sqlTotals + ' SellPriceQty,RubberStamp,OptPriceQty,StatusRecid,LastUpdate_Date,LastUpdate_User,TotalCost,QuantityBracketSelected)'
    select @sqlTotals = @sqlTotals + ' select ConfigRecId,RecId,SellQty' + @QuantitySelected + ',ConfigNum,ConfigDesc,SortOrder,OptionsInMainPrice'
    select @sqlTotals = @sqlTotals + ' ,MarkupPctQty' + @QuantitySelected + ',SellPriceQty' + @QuantitySelected + ',RubberStamp,OptPriceQty' + @QuantitySelected + ',StatusRecid,LastUpdate_Date,LastUpdate_User,TotalCost' + @QuantitySelected + ',' + @QuantitySelected
    select @sqlTotals = @sqlTotals + ' from v_EW_Estimate_Configuration_Totals where ConfigRecId = -3'


    select @sqlLine = 'Insert into tblKP_Estimate_Configuration_Lines'
    select @sqlLine = @sqlLine + '(MstrRfqRecId,RfqRecId,RfqLineRecId,CompanyId,VendorQuoteNum,LineGrp,LineNum,StatusRecId,'
    select @sqlLine = @sqlLine + ' LineDesc,LineSize,LineMatl,LineDeco,LineFinish,CopyFromRecId,PerPieceCost,IsOptional,'
    select @sqlLine = @sqlLine + ' CopyToNewRev,RecId,UnitPrice,LineQty,LinePrice,CustOrVend,SellQty1,RfqNum,ConfigLineIsOptional,ConfigLinePerPieceCost,ConfigLineRecid,SellPrice,SaleQty)'
    select @sqlLine = @sqlLine + ' select distinct MstrRfqRecId,RfqRecId,RfqLineRecId,CompanyId,VendorQuoteNum,LineGrp,LineNum,'
    select @sqlLine = @sqlLine + ' StatusRecId,LineDesc,LineSize,LineMatl,LineDeco,LineFinish,CopyFromRecId,PerPieceCost,IsOptional,'
    select @sqlLine = @sqlLine + ' CopyToNewRev,RecId,UnitPrice' + @QuantitySelected + ',LineQty' + @QuantitySelected + ', isnull(LinePrice' + @QuantitySelected + ', 0.0000),CustOrVend,SellQty' + @QuantitySelected + ',RfqNum,ConfigLineIsOptional,ConfigLinePerPieceCost,ConfigLineRecid,SellPrice' + @QuantitySelected + ',SaleQty' + @QuantitySelected
    select @sqlLine = @sqlLine + ' from v_EW_EstimateLine  where rfqlinerecid in (select RfqLineRecID from kp_tblVendorRfqConfigLine where ConfigRecID = -3) '

    exec( @sqlHeader)
    exec(@sqlTotals)
    exec(@sqlLine)

The good news is a transaction in SQL Server can span multiple batches (each exec is treated as a separate batch.)

You can wrap your EXEC statements in a BEGIN TRANSACTION and COMMIT but you'll need to go a step further and rollback if any errors occur.

Ideally you'd want something like this:

BEGIN TRY
    BEGIN TRANSACTION 
        exec( @sqlHeader)
        exec(@sqlTotals)
        exec(@sqlLine)
    COMMIT
END TRY
BEGIN CATCH

    IF @@TRANCOUNT > 0
        ROLLBACK
END CATCH

The BEGIN TRANSACTION and COMMIT I believe you are already familiar with. The BEGIN TRY and BEGIN CATCH blocks are basically there to catch and handle any errors that occur. If any of your EXEC statements raise an error, the code execution will jump to the CATCH block.

Your existing SQL building code should be outside the transaction (above) as you always want to keep your transactions as short as possible.