(Data Query Language) SQL SELECT. .
SELECT :
SELECT [ALL | DISTINCT] < >|*)
FROM < >
[WHERE <- >]
[GROUP BY < >]
[HAVING <- >]
[ORDER BY < , >]
SELECT , , . . (DISTINCT) (ALL, ). ALL , , , . . < >, , * () . , , , . .
FROM . FROM , SELECT, . , . , , . -, ( ).
WHERE .
GROUP BY .
HAVING -, .
ORDER BY , , . , _, , , , .
WHERE :
{ =, <>, >,<, >=,<= }, .
Between A and . , , . Not Between A and , , , .
|
|
IN () , . . NOT IN (), , .
LIKE NOT LIKE. LIKE , , , , . NOT LIKE .
:
(?) - ( (_));
(*) ( (%));
, , .
IS NULL. , . . : . :
< > IS NULL < > IS NOT NULL.
( ) , IS NULL (TRUE), IS NOT NULL (FALSE), IS NULL , IS NOT NULL .
Null - . , , (. 3).
3.
Not A | and | or | ||
TRUE | TRUE | FALSE | TRUE | TRUE |
TRUE | FALSE | FALSE | FALSE | TRUE |
TRUE | Null | FALSE | Null | TRUE |
FALSE | TRUE | TRUE | FALSE | TRUE |
FALSE | FALSE | TRUE | FALSE | FALSE |
FALSE | Null | TRUE | FALSE | Null |
Null | TRUE | Null | Null | TRUE |
Null | FALSE | Null | FALSE | Null |
Null | Null | Null | Null | Null |
EXIST NOT EXIST. .
.
SELECT . SELECT .