I assume for 1 reason or another you can't use one of the thousands of pre-made stock trade db's that are available already so...
1- Will this be just long stocks/etf's or will it also include MF's, options, warrants, rights, shorts, annuity sub-accounts, etc?
2- are you using ODX or OFX transmissions from the broker?
3- what all are you tracking?
4- do you have the cusip numbers for these stocks or just a symbol or a name?
Anyway, I'll tell you a fraction of what I know about what you are doing (2 tables):
Each security has:
CUSIP (reqd -primary key)
SYMOBL (opt -unique)
NAME (opt)
TYPE (Especially important if you are doing accounting and need to know settlements)
Each transaction has:
TransactionID (reqd -primary key)
CUSIP
DATE
TRANSACTION (-required -buy/sell/sell short?/exercise?/assigned?/grant?)
SHARES
(I assume you also want)
PRICE
COMMISSION
EDIT: this all assumes you're using a USA broker. I'm not sure about cusip's on foreign exchanges.