Hierarchy Data Model

TEACHER

Name

Post

Address

Segment instance – ordered set of fields instances:

TEACHER

Johnson

professor

Kiev

every segment has 0 or 1 parent segment and 0 or more child segments;
root do not have parent segment;
leaves do not have child segments;
twin segments have the same parent segment.

Hierarchy Schema Instance – it is one instance of the root segment and 0 or more instances of the child segments for each instance of the parent segment.

Diana

Helen

Mary

John

Schema Schema instance

Schema Schema instances

Schemas Schemas instances

…

GET UNIQUE

Syntax:

Example:

GET UNIQUE
[WHERE ];

GET UNIQUE TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "SE" AND
TEACHER.Post = "professor";

GET NEXT

GET NEXT
[WHERE ];

Syntax:

Example:

GET NEXT TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "SE" AND
TEACHER.Post = "professor";

GET UNIQUE TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "mathematics" AND
TEACHER.Post = "professor";
...
NT: GET NEXT TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "mathematics " AND
TEACHER.Post = "professor";
...
goto NT

GET NEXT WITHIN PARENT

Syntax:

GET NEXT WITHIN PARENT <тsegment-type>
[WHERE ];

DEPARTMENT.Name = "CAD";
DEPARTMENT.Head = "Nemiroff";
DEPARTMENT.Building = 3;
INSERT DEPARTMENT
WHERE FACULTYТ.Name = "informatics";
TEACHER.Name = "Smith";
TEACHER.Post = “assistant"
TEACHER.Address = "Shevchenko avenue 13/17";
INSERT TEACHER
WHERE FACULTY.Name = "informatics" AND DEPARTMENT.Name = "CAD";

GET HOLD UNIQUE TEACHER
WHERE = FACULTY.Name = "informatics" AND DEPARTMENT.Name = "CAD" AND TEACHER.Name = "Smith";
TEACHER.Address = " Teremkovskaya str. 1/19";
REPLACE;

GET HOLD UNIQUE Teacher
WHERE = Faculty.Name = "informatics" AND
DEPARTMENT.Name = "CAD" AND
TEACHER.Name = "Smith";
DELETE;