Нечто типа этого

EXEC sp_MSForEachTable 'declare @t nvarchar(4000), @from nvarchar(20), @to nvarchar(20)
set @t = ''''
set @from = N''aaa''
set @to = N''bbb''
SELECT @t = @t + c.name + '' = REPLACE('' + c.name + '', '''''' + @from + '''''', '''''' + @to +''''''),'' + char(13)
FROM syscolumns c
INNER JOIN systypes t
ON c.xtype = t.xtype
WHERE id = OBJECT_ID(''?'') AND t.name = ''varchar''
if len(@t) > 0
begin
set @t = ''UPDATE ? SET '' + char(13) + @t
set @t = SUBSTRING(@t, 1, LEN(@t)-2)
EXEC(@t)
end