. SQL , .. . . . . . . , . , . , , , , . , Access, . , .
, . :
CREATE VIEW < >
[(< > [,< > ]...)] AS < SELECT>
, , SELECT. : DROP VIEW < >.
. . :
1. . , , () ;
2. . ;
3. . , ;
4. . ;
5. . , , .
, .
SQL . , . SQL . (CURSOR) SQL ( SELECT). (OPEN < >), (FETCH < >...), , , , (CLOSE < >).
|
|
|
:
CREATE DOMAIN < > [AS]
[DEFAULT < >]
[CHECK (< >)]
SQL : (), , , / . (CHAR(n) CHARACTER(n)) (VARCHAR(n) CHAR VARYING(n) CHARACTER VARYING(n)), n . VARYING , n . (SMALLINT, INT INTEGER) (FLOAT [precision], REAL, DOUBLE PRECISION, NUMERIC(precision, scale), DECIMAL(precision, scale) DEC (precision, scale)), precision , scale . (BIT(n)) (BIT VARYING(n)). / : DATE, TIME TIMESTAMP. DATE TIME , TIMESTAMP . INTERVAL . AS, : Name AS VARCHAR(20).
CHECK , . ,
CREATE DOMAIN sex_type AS CHAR CHECK (VALUE IN (M,F));
IN , IN (SELECT s_type FROM STypes).
ALTER DOMAIN. DROP DOMAIN, :
DROP DOMAIN < > [RESTRICT | CASCADE]
CASCADE , , , .
:
CREATE TABLE < > (< > < > [NOT NULL] [,< > < > [NOT NULL]]...)
. . NOT NULL , . ,
CREATE TABLE ( CHAR(5) NOT NULL, CHAR(8), VARCHAR(20) NOT NULL, DECIMAL(8,2));
:
ALTER TABLE < >
|
|
|
({ADD, MODIFY, DROP} < > [< >] [NOT NULL]
[,{ADD, MODIFY, DROP} < > [< >] [NOT NULL]]...)
(ADD), (MODIFY) (DROP) . ALTER TABLE , CREATE TABLE, . :
ALTER TABLE (ADD VARCHAR(20));
: DROP TABLE < >.
, , . ASSERTION. :
CREATE TABLE < >
{< > < > [NOT NULL] [UNIQUE] [DEFAULT < >] [CHECK (< >)] [, ]}
[PRIMARY KEY (< >), ]
{[UNIQUE (< >), ] [, ]}
{[FOREIGN KEY (< >)] REFERENCES < > [< >] MATCH {PARTIAL | FULL} [ON UPDATE <>] [ON DELETE < >] [, ]} {[CHECK (< >)] [, ]}.
PRIMARY KEY . UNIQUE () . FOREIGN KEY REFERENCES . . SQL : CASCADE, SET NULL, SET DEFAULT, NO ACTION ( ). CHECK . CONSTRAINT < >, ALTER TABLE. ,
CREATE TABLE ( INTEGER PRIMARY KEY, INTEGER, DATE, VARCHAR(255), CONSTRAINT FOREIGN KEY () REFERENCES ON UPDATE CASCADE ON DELETE CASCADE);
:
ALTER TABLE < >
[ADD [COLUMN] < > < > [NOT NULL] [UNIQUE]
[DEFAULT < >] [CHECK (< >)]]
[DROP [COLUMN] < > [RESTRICT | CASCADE]]
[ADD CONSTRAINT < > PRIMARY KEY | UNIQUE | FOREIGN KEY | CHECK]
[DROP CONSTRAINT < > [RESTRICT | CASCADE]]
[ALTER [COLUMN] SET DEFAULT <>]
[ALTER [COLUMN] DROP DEFAULT]
:
CREATE [UNIQUE] INDEX < > ON < > (< > [ASC | DESC] [,< > [ ASC | DESC ]...) [WITH {PRIMARY | DISALLOW NULL | IGNORE NULL}]
. . , . UNIQUE, . , UNIQUE . PRIMARY . UNIQUE , . ASC ( ), DESC. . ,
|
|
|
CREATE INDEX AscName ON (, , );
WITH NULL (DISALLOW NULL) , NULL (IGNORE NULL).
: DROP INDEX < >.
, SQL , . SQL BEGIN TRANSACTION. :
1. COMMIT, . ;
2. ROLLBACK, , , .
3. , SQL.
, SQL , COMMIT, ROLLBACK. SET TRANSACTION (READ ONLY READ WRITE) , , . , , , T1, 2 , 1. : READ UNCOMITED ( ), READ COMMITED ( ), REPEATABLE READ ( ), SERIALIZABLE. SERIALIZABLE ( ), . .
