, , . , . , , , , , . , .
?
. . . :
COUNT NULL , .
SUM .
AVG .
MAX .
MIN .
?
SELECT , , . SUM AVG.
COUNT, MAX, MIN, . , MAX MIN ASCII, , MIN , MAX ( 4).
SUM , , 6.1:
SELECT SUM (amt)
FROM Orders;
=============== SQL Execution Log ============
| SELECT SUM (amt) |
| FROM Orders; |
| ==============================================|
| |
| ------- |
| 26658.4 |
===============================================
6.1. .
, , , , , . - , , GROUP BY ( ). ( 6.2):
SELECT AVG (amt)
FROM Orders;
=============== SQL Execution Log ============
| SELECT AVG (amt) |
| FROM Orders; |
| ==============================================|
| |
| ------- |
| 2665.84 |
===============================================
6.2. .
COUNT
COUNT . , . , DISTINCT, . , , ( 6.3):
|
|
SELECT COUNT (DISTINCT snum)
FROM Orders;
DISTINCT
, DISTINCT, , , SELECT, . DISTINCT COUNT , ANSI, .
=============== SQL Execution Log ============
| SELECT COUNT (DISTINCT snum) |
| FROM Orders; |
| ==============================================|
| |
| ------- |
| 5 |
===============================================
6.3:
(COUNT) DISTINCT , 3, DISTINCT. DISTINCT , , , COUNT. MAX MIN , SUM AVG , .