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The relationship between GIS and standard Quary language "SQL"

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The relationship between GIS and standard Quary language "SQL"

    The relationship between GIS and standard Quary language "SQL"

    The relationship between GIS and standard Quary language "SQL"

    "SQL" Standard search language OR language of arithmetic and logical questions:-

    • It is a non-procedural language comparable to programming languages.
    • Developed by IBM.
    • SQL is the abbreviation for Standard or Structured Query Language.
    • The SQL language includes two languages ​​(arithmetic and logical) (suspicion of arithmetic) combinations.
    • Subtraction, denomination, multiplication, and others (as for territorial suspicion), they are blamed on Boolean Algebra.
    • It depends on three main vocabulary (- AND, OR, NOT.)
    • " E.g. devising the population schedule 1996 and not the population table 2000"

    The basic structure of the language - SQL basic structure is based on three important vocabulary:-

    1. Select Field Attribute (s) (Field in Table).
    2. Choose Table - Form Relation (s) (Table).
    3. condition = +> <- Where Condition.
    Example:-

    - Select (Country – Name And Population)

    - From (Country – Pop)

    - Where (population < 1000000)

    There Are 9 Main Relational Algebra Operations:-

    1- Select:- (Select Tuples {Records} From A Relation).

    2- Project:- (Extract Attributes From a Relation).

    3- Restrict:- (Extract Tuples {Records} From A Relation {Table}).

    4- Union:- (New Relation With All Tuples From Relation).

    5- Intersection:- (New Relation Of Tuples in Both Relation).

    6- Difference:- (A - B) (Tuples Exist in The 1st Relation But Not Exist in The 2st Relation).

    7- Difference:- (B - A) (Tuples Exist in The 1st Relation But Not Exist in The 2st Relation).

    8- Join:- (Take Two Relation Joined By a Common Attribute {Field}).

    9- Product:- (All Possible Combination Of Tuples).
    Some Examples:-


    1- Select → Select (Relation : Tuples)
    ↪Select (Student : Y=3)

    2- Project → project (Relation : Attributes)
    ↪Project (Student : Stud-ID , Grade)

    3- Restrict → Restrict (Relation : Condition)
    ↪Restrict ( Cities : Pop > 100000)

    4- Union → Union (Relation-1 , Relation-2)

    ↪Union (Students , Courses)

    5- Join → Join (Relation : Attribute , Relation : Same Attribute)
    There Are 9 Main Relational Algebra Operations

    Source:-

    DR. Mona Ahmed (2019): GIS1 Lectures , Maps Division, Cairo University

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