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Since we have started dealing with
numbers, the next natural question
to ask is if it is possible to do
math on those numbers, such as
summing them up or taking their
average. The answer is yes! SQL
has several arithematic functions,
and they are:
- AVG
- COUNT
- MAX
- MIN
- SUM
The syntax for using functions
is,
SELECT
"function type"("column_name")
FROM "table_name"
For example, if we want to get the
sum of all sales from the
following table,
Table Store_Information
| store_name |
Sales |
Date |
| Los Angeles |
$1500 |
Jan-05-1999 |
| San Diego |
$250 |
Jan-07-1999 |
| Los Angeles |
$300 |
Jan-08-1999 |
| Boston |
$700 |
Jan-08-1999 |
we would type in
SELECT
SUM(Sales) FROM Store_Information
Result:
SUM(Sales)
$2750
$2750 represents the sum of all
Sales entries: $1500 + $250 + $300
+ $700.
In addition to using functions,
it is also possible to use SQL to
perform simple tasks such as
addition (+) and subtraction (-).
For character-type data, there are
also several string functions
available, such as concatenation,
trim, and substring functions.
Different RDBMS vendors have
different string functions
implementations, and it is best to
consult the references for your
RDBMS to see how these functions
are used.
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