understanding relational database query languages winrdbi windows-based relational database...

Understanding Relational Database Query Languages

WinRDBI Windows-based Relational DataBase Interpreter

http://winrdbi.asu.edu/

An educational tool that provides an interactive approach to learning relational database query languages.

Relational algebra Domain Relational Calculus (DRC) Tuple Relational Calculus (TRC) SQL


WinRDBI Online Demonstrations

Look for online demonstrations of the software on the WinRDBI web:

http://winrdbi.asu.edu/ Getting Started with WinRDBI Creating a Database in WinRDBI

Additional demonstrations will be added over time.


User Interface

Multiple Query Panes: one query language is associated with each pane;

result of queries displayed in the bottom subwindow of the query pane

One Schema Pane: displays the schema and instance of the currently opened relational database


ICONS

new database paste

new query new table

open delete table

save insert tuple

save all delete tuple

print find

cut replace

copy execute


Syntax Conventions

Since the heart of WinRDBI is written in Prolog (with Java used for the graphical user interface), the following Prolog conventions are assumed:

constants:numeric constants and single-quoted strings

relation and attribute names:identifiers starting with a lowercase letter

variable names:identifiers starting with an uppercase letter


Relational Algebra Syntax Summary

Fundamental Operators (r)

{ t | t r and } ai,…,aj(r)

{ t.ai, …, t.aj | t r } r s

{ t | t r or t s } r - s

{ t | t r and t s} q × r

{ tqtr | tq q and tr r }

Additional Operators r s

r - ( r - s ) p q

(p × q)

p qP Q( (p × q) )where = (p.ai=q.ai and … and p.aj=q.aj) P Q = {ai, …, aj}

p qP - Q (p) - P - Q ((P - Q (p) × q) - p)


Relational Algebra WinRDBI Syntax SummaryWinRDBI

select condition (r) project ai, …, aj (r) r union s r difference s q product r r intersect s p njoin q: WinRDBI does not provide

division and -join operators to encourage the use of the fundamental relational algebra operators.

Formal Relational Algebra condition(r)

ai,…,aj(r)

r s r - s q × r r s p q


Domain Relational CalculusSyntax Summary

{ D1, …, Dn | FF (D1, …, Dn) }

F F describes the properties of the data to be retrieved.

The output schema of FF is given by the domain variables

D1, …, Dn that act as global variables in FF.

The result of the DRC expression gives the set of all tuples

(d1, d2, …, dn) such that when di is substituted for Di

(1 =< i =< n), FF is true.


Domain Relational CalculusAtoms & Formulas

LetDi be a domain variablec be a domain constant be a comparison operator

Atoms r(D1, D2, …, Dn) Di Dj

Di c

Let FF, F1F1 and F2F2 be formulas

Formulas ( FF ) not FF F1F1 and F2F2 F1F1 or F2F2

Let D be free* in FF(D) (exists D) FF(D) (forall D) FF(D)

* a variable is free in a formula if it is not quantified by exists or forall


Domain Relational CalculusValid Expression

{ D1, …, Dn | FF (D1, …, Dn) }

is a valid DRC expression if it has only the variables appearing to the left of the vertical bar | free in FF.Any other variable appearing in FF must be bound.

free vs. bound variables free (global): variable is not explicitly quantified bound (free): variable is declared explicitly through

quantification and its scope is the quantified formula


Domain Relational CalculusRelational Completeness

condition (r):

{ R1, …, Rn | r(R1, …, Rn) and condition}

ai,…,aj(r):

{ Ri, …, Rj | r(R1, …, Ri, …, Rj, …, Rn)}

r s:

{ D1, …, Dn | r(D1, …, Dn) or s(D1, …, Dn) }

r - s:

{ D1, …, Dn | r(D1, …, Dn) and not s(D1, …, Dn) }

q × r :

{ Q1, …, Qm, R1, …, Rn | q(Q1, …, Qm) and r(R1, …, Rn) }


Tuple Relational CalculusSyntax Summary

{ T1, …, Tn | FF (T1, …, Tn) }

F F describes the properties of the data to be retrieved.

The output schema of FF is given by the tuple variables

T1, …, Tn that act as global variables in FF.


Tuple Relational CalculusAtoms & Formulas

LetT and Ti be tuple variablesaj be an attributec be a domain constant be a comparison operator

Atoms r(T) Ti.am Tj.an

T.ai c

Let FF, F1F1 and F2F2 be formulas

Formulas ( FF ) not FF F1F1 and F2F2 F1F1 or F2F2

Let T be free* in FF(T) (exists T) FF(T) (forall T) FF(T)

* a variable is free in a formula if it is not quantified by exists or forall


Tuple Relational CalculusValid Expression

{ T1, …, Tn | FF (T1, …, Tn) }

is a valid TRC expression if it has only the variables appearing to the left of the vertical bar | free in FF.Any other variable appearing in FF must be bound.

free vs. bound variables free (global): variable is not explicitly quantified bound (free): variable is declared explicitly through

quantification and its scope is the quantified formula


Tuple Relational CalculusRelational Completeness

condition (r):

{ R| r(R) and condition}

ai…,aj(r):

{ R.ai, …, R.aj | r(R)}

r s:

{ T | r(T) or s(T) }

r - s:

{ T | r(T) and not s(T) }

q × r :

{ Q, R | q(Q) and r(R) }


SQLSimple Query Syntax

select distinct a1,…,am

from r1, r2, …, rn

where condition

is equivalent to

a1,…,am ( condition (r1 × r2 × … × rn) )


SQLRelational Completeness

condition(r)

A (r)

r s

r - s

q × r

select * from r where condition

select distinct A from r

select * from r union select * from s

select * from r except select * from s

select * from q, r


SQLQuery Syntax Summary

select [distinct] ATTRIBUTE-LIST

from TABLE-LIST

[where WHERE-CONDITION]

[group by GROUPING-ATTRIBUTES

[having HAVING-CONDITION]]

[order by COLUMN-NAME [asc | desc], … ]


SQLData Definition Syntax Summary

create table TABLE-NAME(COL-NAME COL-TYPE [ATTR-CONSTRAINT],…[TABLE-CONSTRAINT-LIST])where

ATTR-CONSTRAINT: not null or default value

TABLE-CONSTRAINT-LIST: primary key, uniqueness and referential integrity(foreign key)


SQLInsert Syntax Summary

insert into TABLE-NAME [ (ATTRIBUTE-LIST)]

SOURCE

where SOURCE is one of:

values ( EXPLICIT-VALUES)

SELECT-STATEMENT


SQLUpdate & Delete Syntax Summary

update TABLE-NAME

set COLUMN-NAME = VALUE-EXPR, …

[where UPDATE-CONDITION]

delete from TABLE-NAME

[where DELETE-CONDITION]


SQLWinRDBI Syntax Summary

Since WinRDBI has an integrated GUI for defining and

manipulating the database, WinRDBI SQL supports only

the query language.

SQL-89 compatibility: no joined tables in the from clause

Does not support SQL-standard view definition: assumes

intermediate table syntax across all query languages

Language simplification disallows aggregation in a nested

subquery: use two queries instead ...


SQLAggregation in Nested Queries

SQL

select E.eID, E.eLast, E.eFirst, E.eTitlefrom employee E where E.eSalary =

(select min(S.eSalary) from employee S );

WinRDBI

minimumSalary(minSalary) := select min(E.eSalary) from employee E;

select E.eID, E.eLast, E.eFirst, E.eTitlefrom employee E where E.eSalary =

(select minSalary from minimumSalary);

understanding relational database query languages winrdbi windows-based relational database...

Documents

q p q p q p

p q p q p p

s p q p qp q p q p q

aj p q

aj t r

query paneone schema

additional operatorsr

sp njoin q