WinRDBI Windows-based Relational DataBase Interpreter

Understanding Relational Database Query Languages

WinRDBI Windows-based Relational DataBase Interpreter

http://www.eas.asu.edu/~winrdbi

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


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 pastenew query new tableopen delete tablesave insert tuplesave all delete tupleprint findcut replacecopy 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 q

P 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


Relational AlgebraWinRDBI Demo

Illustrate the features of the relational algebra language by example using the employee training enterprise that can be found at

http://www.prenhall.com/dietrich


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 formulasFormulas

( 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) }


Domain Relational CalculusWinRDBI Demo

Illustrate the features of the DRC language by example using the employee training enterprise that can be found at



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 formulasFormulas

( 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) }


Tuple Relational CalculusWinRDBI Demo

Illustrate the features of the TRC language by example using the employee training enterprise that can be found at



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 valueTABLE-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);


SQLWinRDBI Demo

Illustrate the features of the SQL language by example using the employee training enterprise that can be found at


Documents

WinRDBI Windows-based Relational DataBase Interpreter