556___________________________________________ 10

      UNIQUE ,  -
     .        -
   .

       DEFAULT  -
   . :

CREATE TABLE Pers(

Num smallint Not Null Primary Key,

Dep char(15),

Fam char(20) Not Null,

Nam char(20) Not Null,

Par char(20) Not Null,

Year_b smallint DEFAULT 1950,

Sex char(l) DEFAULT ''
) ;

      .   
     COMPUTED BY,   
,   . , 

CREATE TABLE Pers(

Num smallint Not Null Primary Key,

Fam char(20) Not Null,

Nam char(20) Not Null,

Par char(20) Not Null,

Year_b smallint DEFAULT 1950,

Age COMPUTED BY (2000 - Year_b)
) ;

   Age,     
  .

        .
, 

CREATE TABLE Pers(

Num smallint Not Null Primary Key,

Fam char(20) Not Null,

Nam char(20) Not Null,

Par char(20) Not Null,

Year_b smallint DEFAULT 1950

CHECK;(Year_bl917)and(Year_b))
) ;

    :  1917   1980. -
     CHECK.

          
.    :

FOREIGN KEY (  -   )
REFERENCES   

    
ON DELETE 
ON UPDATE 

     FOREIGN KEY    .
,  ,       :

().      '
   REFERENCES  ,   '
   .

    ON DELETE  ON UPDATE 
,    ,     -
  .   :