MS SQL Error converting datatype varchar to numeric

Hi,

Below I have a stored procedure that I am currently working on, When I run this stored procedure i get the following error:

Msg 8114, Level 16, State 5, Procedure SP_plottotals, Line 26
Error converting data type varchar to numeric.

Select allOpen in new window

What am I doing wrong? The plot#_total column in the database is set to decimal(18,2) as the data type.

I am trying to select the SUM of a column from a table into a variable in the first statement and then updating another column with the value of the SUM variable in the second statement.

The Procedure is:

/*
  [SP_plottotals] 243, 1
*/
ALTER PROCEDURE [dbo].[SP_plottotals]
	-- Add the parameters for the stored procedure here
     @PKCPID int
    ,@plot int
    
AS

DECLARE @i int
DECLARE @sql nvarchar(500)
DECLARE @plottotal decimal(18,2)


set @i = 1
WHILE (@i <= (400))
BEGIN


set @sql = '
SELECT '+@plottotal+' = SUM(plot'+cast(@plot as varchar(100))+'_total) FROM tblprojects_plantlist WHERE FKCPID='+cast(@PKCPID as varchar(100))+''

print @sql

exec sp_executesql @sql

END

DECLARE @i2 int
DECLARE @sql2 nvarchar(500)


set @i2 = 1
WHILE (@i2 <= (400))
BEGIN


set @sql2 = '
 UPDATE
	tblplotinvoicing
SET
	plot'+cast(@plot as varchar(100))+'_total = '+cast(@plottotal as varchar(200))+'
WHERE FKCPID='+cast(@PKCPID as varchar(100))+''

print @sql2

exec sp_executesql @sql2

END

Select allOpen in new window

Thanks.