Query Design

hi

i am new to t-sql. the problem is i have to subtract a field from a column A in table X from a field in Column R from Table Y and put the subtracted value in the Column K in the Table Z

ex:

Table Name: Order
Field Name: Boxes

Table Name: Despatch
Field Name: Boxes

Table Name: Balance
Field Name: Boxes

the problem is i have to subtract the values(Boxes) in the table Despatch, from the values(Boxes) in the table Order, and the subtracted value has to be put in values(Boxes) in the table Balance.


can any one help?

one more thing: Where i can get the basics of t-sql



regards.,

sekar.r