Mavzu: sqlda Alter instruksiyalari

CREATE DOMAIN Dtug_yil INT(kirish)
CHECK VALUE BETWEEN (orasidagi qiymatni tekshirish)1960 AND 1989
CREATE TABLE talaba (id_talaba INTEGER PRIMARY KEY(asosiy kalit),
reyt_nom CHAR(8) NOT NULL UNIQUE,
familiya VARCHAR (40) NOT NULL,
ismi VARCHAR(40) NOT NULL,
sharifi VARCHAR(40),
id_millati INTEGER,
jinsi Jjnsi,
pas_ser CHAR(2) NOT NULL,
pas_nom CHAR(8) NOT NULL,
tug_yil Tug_yil,
manzil VARCHAR(255),
Sanoq son ko`rinishiDECIMAL (6,2),
tug_joy VARCHAR (50) DEFAULT (vaziyat)‘Toshkent’,
id_tum INTEGER,
id_ray INTEGER,
id_fak INTEGER,
stipendiya INTEGER,
UNIQUE (pas_ser, pas_nom),
CONSTRAINT (cheklash)Millat
FOREIGN KEY (tashqi kalit) (id_millati)
REFERENCES millatlar
ON DELETE SET NULL, (tarmoqning null holati)
CONSTRAINT Oblast
FOREIGN KEY (id_vil)
REFERENCES viloyat
ON DELETE SET NULL,
CONSTRAINT Rayon
FOREIGN KEY (id_ray)
REFERENCES tumanlar
ON DELETE SET NULL,
CONSTRAINT Fakul
FOREIGN KEY (id_fak)
REFERENCES fakultet
ON DELETE CASCADE (kaskadni o‘chirish)
ON UPDATE CASCADE)
Jadval tavsifini o‘zgartirish
Jadval yaratilgandan keyin uni tuzilishini o‘zgartirish uchun ALTER TABLE operatori qo‘llanadi, bu operator yordamida quyidagi ishlovlarni amalga oshirish mumkin:

• 
  jadvalga yangi ustun kiritish;
  
• 
  jadvaldan ustunni o‘chirish;
  
• 
  jadval uchun yangi chegaralanishlar kiritish;
  
• 
  jadval chegaralanishlarini o‘chirish;
  
• 
  ustun uchun kelishuv qiymatlarini o‘rnatish;
  
• 
  kelishuv qiymatlarni o‘chirish.
  

Bu operatorning formati quyidagicha:
<jadval o‘zgartirish>::= ALTER TABLE <jadval nomi>
{ADD (qo‘shish) [ COLUMN (ustun)] {<ustun nomi>
{<domen nomi> | <berilgan turi>}
[ NOT NULL | NULL ] [ UNIQUE ]
[<kelishuv bo‘yicha qiymat>] [<check chegarasi>]} [, . . . ]
| DROP (qoplash)[ COLUMN ] {<ustun nomi>
[ RESTRICT (cheklsh) | CASCADE ] }(kaskadni chegaralsh) [, . . . ] | {ADD <chegara tavsifi>} [, . . . ]
| DROP CONSTRAINT {<chegara nomi>
[ RESTRICT | CASCADE ] } [, . . . ]
| ALTER [ COLUMN ] { <ustun nomi>