Aggregation
Syntax:
SELECT f(x) ...... FROM T
Parameter:
|
T |
Table name |
|
f(x) |
Aggregate function f on generalized field expression x |
Example:
|
SELECT SellerID,sum(Amount) FROM ReturnedPmt BY SellerID |
Group by SellerID and sum values under Amount field |
|
SELECT CustomerID.CustName, sum(Amount) Total FROM ReturnedPmt BY CustomerID |
|
Learning point:
1) A primary table is a table where part of the primary key is pointed by the foreign key in another table; a dimension table of a level function with a single-field primary key; the primary table’s primary table; a homo-dimension table’s primary table; the primary table’s homo-dimension table. The last case requires that primary keys of the primary table and the sub table correspond in order.
1)