Storing FTSE stock data
What I would do is to create a table with the stock_id (that can be the alphanumeric code or a integer), the timestamp of the measurement and the current value. That is your entry data, 3 columns. 

From that point you can add columns for calculations (the difference absolute or percent) with the previous value. Having all in the same table will simplify the model and ease your queries. Try to create a date (not timestamp) column and create a partition by it. It may lighten a bit the access to the table as long as you set it in your queries.