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ZAMYLA CHAN: For buy,
we'll also want to display

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a form for users to specify
which stock they want to buy

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and the number of shares of that
stock they'd like to purchase.

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So again, it sounds like it's time to
add another template to our directory.

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Then we'll want to add that
stock to the user's portfolio

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if they have enough cash and
update their cash as appropriate.

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For the display form, let's
ask for the symbol of the stock

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and the number of shares-- of course
checking if this is valid input.

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Now that we know how many
shares of a particular stock

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the user wants to purchase, let's
see if they can actually afford it.

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Select the cash column from the table
users where the ID number equals 1.

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And if that cash exceeds the
total value of the shares

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times the price of that stock, then
I can go ahead and buy that stock.

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If they can indeed afford it, then let's
add that stock to the user's portfolio.

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In the portfolio we'll want to keep
track of how many shares of each stock

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the user has.

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Now the user's table that we
have within our SQL database

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doesn't have the capability
to store that information yet

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because our user's table simply
has the user name, the user

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ID, and the hash of their password.

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So in addition to our users table
we're going to want to add another one,

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whether we call that "portfolio"
or "transactions" or "history"

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or any other appropriate name that
reflects the type of table it is.

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Within this table or perhaps
combination of tables--

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you could have to if
you so choose-- we want

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to keep track of who
bought what at what price

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and when using the appropriate
SQLite types for the values

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that we're inserting, defining unique
indices on any fields that should

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be unique, and then non-unique indices
on any fields that we may be searching.

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After successfully updating
the user's virtual portfolio,

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let's also update the cash to reflect
the purchase that they just made.

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Remember that a user's cash
is stored in the user's table.

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So, if I have my user with
ID number one and they just

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bought $50 worth of shares, then
I'll execute the update query.

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Update the user's table,
setting cash equal

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to cash minus 50 where my
user is user with ID 1.

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Now let's edit the landing page.

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