static void WriteColumns(SqlWriter writer, IEnumerable<string> columns, bool separateLines = false)
		{
			var separator = (string)null;
			foreach (var column in columns)
			{
				if (separator != null)
				{
					writer.Write(separator);
					if (separateLines)
						writer.WriteLine();
				}
				writer.Write(column);
				separator = ", ";
			}
		}