There are times when you may be inserting data from one table to another and you get the message:
String or binary data would be truncated
This is often because the data in the source table is too large for the data in the destination table. I’ve created the below script to quickly identify what field may be the culprit. Change the from and to table variables to represent the names of the tables you want to compare.
/* Dynamic script to compare two tables' character fields. Useful when getting message that string or binary data will be truncated or if you set the from and to tables to be the same, can show how much data is actually being used in text fields compared to their size. */ /* dynamic unpivot adapted from: https://dba.stackexchange.com/questions/48393/passing-column-names-dynamically-to-unpivot * thanks to https://stackoverflow.com/questions/19055902/unpivot-with-column-name for identifying how to get the column name into the result (duh) */ /* Setup variables below: * from tables should be where data is coming from - the table must contain data for this query to work * to tables should be where data is being inserted to */ declare @schema_name_from nvarchar(max) = 'dbo' declare @table_name_from nvarchar(max) = 'HVDHB_IP_Staging' /* this table must have data to be able to perform the comparison */ declare @schema_name_to nvarchar(max) = 'dbo' declare @table_name_to nvarchar(max) = 'HVDHB_IP' DECLARE @colsUnpivot AS NVARCHAR(MAX), @colsMaxLength as nvarchar(max), @sql AS NVARCHAR(MAX) /* We want to form a list of columns names, one separated purely by commas, and the second applying the function we want to identify the maximum size of the data contained with each column */ select @colsUnpivot = string_agg(quotename(column_name), ',') from ( select distinct column_name from INFORMATION_SCHEMA.COLUMNS where ( table_name = @table_name_from and TABLE_SCHEMA = @schema_name_from and DATA_TYPE in ('nchar','nvarchar','varchar','char') ) OR ( table_name = @table_name_to and TABLE_SCHEMA = @schema_name_to and DATA_TYPE in ('nchar','nvarchar','varchar','char') ) ) x /* In this query, we must caset the result for each column to integer, otherwise the result comes out as the * base datatype. It is then not possible to combine varchar(max) with varchar(n). By casting to integer * we get the counts coming through as integer, and we don't suffer the same issue. */ select @colsMaxLength = string_agg(quotename(column_name)+'=cast(isnull(max(len('+quotename(column_name)+')),0) as integer)', ',') from INFORMATION_SCHEMA.COLUMNS where table_name = @table_name_from and table_schema = @schema_name_from and data_type In ('varchar','nvarchar','char','nchar') /* This SQL gets the data size in the 'from' table and unpivots it so it can be compared * to the column definitions returned from INFORMATION_SCHEMA.COLUMNS table. */ select @sql = ' /* calculate the data sizes within the from table */ with source_wide as ( SELECT '+@colsMaxLength+' from '+quotename(@schema_name_from)+'.'+quotename(@table_name_from)+' ), /* unpivot the data from wide to long format */ source_long as ( select SourceColumnName = d, SourceSize = data from source_wide unpivot(data for d in ('+@colsUnpivot+')) as unpvt ), /* get the column definitions in the to table, in long format */ target_long as ( select TargetColumnName = column_name, TargetSize = CHARACTER_MAXIMUM_LENGTH from INFORMATION_SCHEMA.COLUMNS where table_name = '''+@table_name_to+''' and table_schema = ''' + @schema_name_to + ''' and data_type In (''varchar'',''nvarchar'',''char'',''nchar'') ), /* generate calculated fields */ output as ( select *, Status = case when SourceSize > TargetSize then ''Source too large'' else ''OK'' end, SizeDifference = TargetSize - SourceSize from source_long S full outer join target_long T on S.SourceColumnName = T.TargetColumnName ) /* final output */ select * from output order by Status desc ' print @sql exec sp_executesql @sql alter table HVDHB_IP alter column DischargeMap varchar(3)