How to determine of if columns exist in one table and not another and alter the table

Hi-

You can use a SQL statement like below against the INFORMATION_SCHEMA to build dynamic ALTER TABLE statements.

The query will return for you the columns and associated information that are in the live table that do not exist with same name in the backup table.

You can then use columns like COLUMN_NAME, COLUMN_DEFAULT, IS_NULLABLE, DATA_TYPE, et cetera to build your ALTER TABLE {backup table name} ADD ... statements.
http://msdn.microsoft.com/en-us/library/aa275462(SQL.80).aspx

Hope that helps!

Kevin

select *
from information_schema.columns c1
where c1.TABLE_NAME = '{live table name}'
and not exists (
   select null
   from information_schema.columns c2
   where c2.TABLE_NAME = '{backup table name}'
   and c2.COLUMN_NAME = c1.COLUMN_NAME
);

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Say your tables are t_1 and t_2

declare @sql varchar(8000)
set @sql = ''
select @sql = @sql + 'alter table t_2 add ' + quotename(c.name) + ' ' + t.name +
case
when t.name in (
	'varbinary','varchar','binary','char','nchar','float',
	'time','datetime2','datetimeoffset')
	then '(' + right(c.xprec,10) + ')'
when t.name = 'nvarchar'
	then '(' + right(c.length/2,10) + ')'
when t.name in ('decimal','numeric')
	then '(' + right(c.xprec,10) + ',' + right(c.xscale,10) + ')'
else
	''
end
+ ';'
from 
(
select a.*
from
(select c.* from sysobjects o inner join syscolumns c on c.id=o.id where o.name = 't_1') a
left join
(select c.* from sysobjects o inner join syscolumns c on c.id=o.id where o.name = 't_2') b
on a.name=b.name
where b.name is null
) c
inner join systypes t on t.xtype=c.xtype and t.xusertype = c.xusertype
;
--print @sql
exec (@sql)

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I am getting a Msg 1001, Level 15, State 1, Line 1
Line 1: Length or precision specification 0 is invalid.

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