Relationenalgebra auf der Kommandozeile
Attribut
Tupel
R=Relation u¨berA1,…,Ak und β⊆A1,…,Ak.R = \text{Relation über} {A_1, …, A_k} \text{ und }β ⊆ {A_1, …, A_k}. R=Relation u¨berA1,…,Ak und β⊆A1,…,Ak.πβ(R):={tβ∣t∈R}\pi_{\beta}(R):=\{t_{\beta}|t \in R\} πβ(R):={tβ∣t∈R}
R=Relation u¨berA1,…,Ak und β⊆A1,…,Ak.R = \text{Relation über} {A_1, …, A_k} \text{ und }β ⊆ {A_1, …, A_k}. R=Relation u¨berA1,…,Ak und β⊆A1,…,Ak.
πβ(R):={tβ∣t∈R}\pi_{\beta}(R):=\{t_{\beta}|t \in R\} πβ(R):={tβ∣t∈R}
SELECT CustomerName, City FROM Customers;
σA(R):={t∣t∈R∧t erfu¨llt A}\sigma_{\text{A}}(R) := \{ t | t \in R \wedge t \text{ erfüllt A} \} σA(R):={t∣t∈R∧t erfu¨llt A}
SELECT * FROM Customers
WHERE Country LIKE '%ada%';
R∪S:={t∣t∈R∨t∈S}R \cup S := \{ t | t \in R \lor t \in S \} R∪S:={t∣t∈R∨t∈S}
SELECT * FROM Customers_A
UNION SELECT * FROM Customers_B
R−S:=R∖S:={t∣t∈R∧t∉S}R {-} S := R {\setminus} S := \{ t | t \in R \land t \notin S \} R−S:=R∖S:={t∣t∈R∧t∈/S}
EXCEPT SELECT * FROM Customers_B;
ρ[neu←alt](R):={t′∣t′(R−alt)=t(R−alt)∧t′(neu)=t(alt)}\rho_{[\mathrm{neu}\leftarrow\mathrm{alt}]}(R):= \{t'|t'(R-\mathrm{alt})=t(R-\mathrm{alt}) \land t'(\mathrm{neu})=t(\mathrm{alt})\} ρ[neu←alt](R):={t′∣t′(R−alt)=t(R−alt)∧t′(neu)=t(alt)}
R×S:={(a1,a2,...,an,b1,b2,...,bm)∣(a1,...,an)∈R∧(b1,...,bm)∈S}R\times S:=\{(a_1,a_2,...,a_n,b_1,b_2,...,b_m)| \\ (a_1,...,a_n)\in R\wedge (b_1,...,b_m)\in S\} R×S:={(a1,a2,...,an,b1,b2,...,bm)∣(a1,...,an)∈R∧(b1,...,bm)∈S}
SELECT * FROM R, S;
cat,sed, grep, cut, awk, join, comm, diff, uniq und sort
http://matt.might.net/articles/sql-in-the-shell/
https://github.com/eigenfunk/sql-in-the-shell
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Relation: Attribute und Tupel. Attribut: Typ Tupel: Geordnete Werte, Datensatz.