dqoder/sql2rela

sql to relational algrebra

Translator - SQL to Relation algebra

Develop a translator which shall translate a given select statement of SQL into an equivalent expression in relational algebra. Your translator must include SELECTION, PROJECTION, JOIN and SET operation.

Note: no subqueries

examples

SELECT A, B
	FROM r
	WHERE A > 100

$\Pi_{A,B}(\sigma_{A>100}(r))$

SELECT *
	FROM r
	WHERE A > 100

sigma_{A>100}(r) $\sigma_{A>100}(r)$

SELECT *
	FROM r JOIN s
	WHERE A > 100

$\sigma_{A>100}(r \Join s)$

SELECT A
	FROM r
INTERSECT
SELECT A
	FROM s

$\Pi_{A}$(r) $\cap$ $\Pi_{A}$(s)

Plan

lexical analysic $\rightarrow$ parsing $\rightarrow$ substitution

symbols

SQL operation	relational algebra
SELECTION	$\sigma$
PROJECTION	$\Pi$
UNION	$\cup$
INTERSECTION	$\cap$
SET DIFFERENCE	$\minus$
LEFT JOIN	$\leftouterjoin$
RIGHT JOIN	$\rightouterjoin$
FULL OUTER JOIN	$\fullouterjoin$
INNER JOIN	$\bowtie$

grammar

S $\rightarrow$ S₀ | S₀ T_set S₀

S₀ $\rightarrow$ T_s A T_f R T_w C

R $\rightarrow$ T