Using Nested WITH Element References
The following example introduces the first level of complexity.
Q: Who are grandparents?
Finding who are grandparents could be achieved by a joining of two isparent references but, as before, we will define the gender specific elements and union them.
The complexity arises when you notice that:
ismother and isfather are both present in the definition of isparent.
ismother and isfather are also both present in the definition of isgrfather and isgrmother, both of which also refer to isparent.
For this to work, the instances of ismother and isfather must be distinct in the join from those expanded in isparent. Now it is seen why this acts like an inline view: Although the elements are defined once, nested references between these cause recursive replication of derived tables to the referenced elements.
WITH
ismother(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='F'
),
isfather(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='M'
),
isparent(name, child) AS (
SELECT name,child FROM ismother
UNION ALL
SELECT name,child FROM isfather
),
isgrfather(name, grchild) AS (
SELECT f.name,p.child
FROM isfather f JOIN isparent p ON f.child=p.name
),
isgrmother(name, grchild) AS (
SELECT f.name,p.child
FROM ismother f JOIN isparent p ON f.child=p.name
)
SELECT name,'isgrfather',grchild FROM isgrfather
UNION ALL
SELECT name,'isgrmother',grchild FROM isgrmother
ORDER BY 2,1,3;
grandparents
name col2 grchild
--------- ----------- -----------
Dad isgrfather Daugtr
Dad isgrfather Niece
Dad isgrfather Nephew
Dad isgrfather Son
GrDad isgrfather Bro
GrDad isgrfather Cousin
GrDad isgrfather Me
GrDad isgrfather Sis
GrDad isgrfather StSis
GrGrDad isgrfather Aunt
GrGrDad isgrfather Dad
GrGrDad isgrfather Uncle1
GrGrDad isgrfather Uncle2
Me isgrfather GrDaugtr
Me isgrfather GrSon
GrGrMa isgrmother Aunt
GrGrMa isgrmother Dad
GrGrMa isgrmother Uncle1
GrGrMa isgrmother Uncle2
GrMa isgrmother Bro
GrMa isgrmother Cousin
GrMa isgrmother Me
GrMa isgrmother Sis
GrMa isgrmother StSis
Mom isgrmother Daugtr
Mom isgrmother Niece
Mom isgrmother Nephew
Mom isgrmother Son
Q: Who are brother and sister?
To further illustrate nested CTEs, we ask the question, "Who are brother and sister?"
We can define a sharefather (and a sharemother) by checking each pairing of persons with whether there exists a third person such that the relationship isfather (or ismother) holds for both. Taking a union of these gives the answer:
WITH
ismother(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='F'
),
isfather(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='M'
),
isparent(name, child) AS (
SELECT f.name, f.child FROM isfather f
UNION ALL
SELECT m.name, m.child FROM ismother m
),
sharefather(name, sibling, father) AS (
SELECT a.child,b.child,a.name
FROM isfather a JOIN isfather b
ON a.name=b.name AND a.child<b.child
),
sharemother(name, sibling, mother) AS (
SELECT a.child,b.child,a.name
FROM ismother a JOIN ismother b
ON a.name=b.name AND a.child<b.child
)
SELECT name, sibling FROM sharefather UNION
SELECT name, sibling FROM sharemother ORDER BY 1,2;
issibling
name sibling
-------- -------
Aunt Dad
Aunt Uncle1
Aunt Uncle2
Bro Me
Bro Sis
Bro StSis
Dad Uncle1
Dad Uncle2
Daugtr Son
GrDaugtr GrSon
Me Sis
Me StSis
Sis StSis
Uncle1 Uncle2
Q: Who are full siblings?
Noting that the previous result includes a few step relations suggests a query to determine only full siblings by joining sharefather and sharemother:
WITH
ismother(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='F'
),
isfather(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='M'
),
isparent(name, child) AS (
SELECT f.name, f.child FROM isfather f
UNION ALL
SELECT m.name, m.child FROM ismother m
),
sharefather(name, sibling, father) AS (
SELECT a.child,b.child,a.name
FROM isfather a JOIN isfather b
ON a.name=b.name AND a.child<>b.child
),
sharemother(name, sibling, mother) AS (
SELECT a.child,b.child,a.name
FROM ismother a JOIN ismother b
ON a.name=b.name AND a.child<>b.child
),
issibling(name,sibling,mother,father) AS (
SELECT sf.name,sf.sibling,sm.mother,sf.father
FROM sharefather sf JOIN sharemother sm
ON sf.name=sm.name AND sf.sibling=sm.sibling
)
SELECT * FROM issibling
ORDER BY 1, 2;
full siblings
name sibling mother father
------------ --------------- ------------ ----------
Aunt Dad GrMa GrDad
Aunt Uncle1 GrMa GrDad
Aunt Uncle2 GrMa GrDad
Bro Me Mom Dad
Bro Sis Mom Dad
Dad Aunt GrMa GrDad
Dad Uncle1 GrMa GrDad
Dad Uncle2 GrMa GrDad
Me Bro Mom Dad
Me Sis Mom Dad
Sis Bro Mom Dad
Sis Me Mom Dad
Uncle1 Aunt GrMa GrDad
Uncle1 Dad GrMa GrDad
Uncle1 Uncle2 GrMa GrDad
Uncle2 Aunt GrMa GrDad
Uncle2 Dad GrMa GrDad
Uncle2 Uncle1 GrMa GrDad
Q: Who are aunts and uncles?
If we add elements isson and isdaughter then we can also derive hasnephew and hasniece based on the other tables.
WITH
ismother(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='F'
),
isfather(name, child) AS (
SELECT parent,r.name
FROM person p JOIN relatives r ON p.name=r.parent AND gender='M'
),
isparent(name, child) AS (
SELECT f.name, f.child FROM isfather f
UNION ALL
SELECT m.name, m.child FROM ismother m
),
sharefather(name,sibling,father) AS (
SELECT p2.name,p3.name,a.name
FROM person p2,person p3,isfather a JOIN isfather b ON a.name=b.name
WHERE p2.name<>p3.name AND a.child=p2.name AND b.child=p3.name
),
sharemother(name,sibling,mother) AS (
SELECT p2.name,p3.name,a.name
FROM person p2, person p3,ismother a JOIN ismother b ON a.name=b.name
WHERE p2.name<>p3.name AND a.child=p2.name AND b.child=p3.name
),
issibling AS (
SELECT sf.name,sf.sibling,sf.father,sm.mother
FROM sharefather sf JOIN sharemother sm
ON sf.name=sm.name AND sf.sibling=sm.sibling
),
isson(name, mother, father) AS (
SELECT p1.name,ms.name,fs.name
FROM person p1 LEFT OUTER JOIN isfather fs
ON p1.name=fs.child
LEFT OUTER JOIN ismother ms
ON p1.name=ms.child
WHERE p1.gender='M'
),
isdaughter(name, mother, father) AS (
SELECT p1.name,md.name,fd.name
FROM person p1 LEFT OUTER JOIN isfather fd
ON p1.name=fd.child
LEFT OUTER JOIN ismother md
ON p1.name=md.child
WHERE p1.gender='F'
),
hasnephew(name, nephew, sibling) AS (
SELECT i.name,s.name,i.sibling
FROM issibling i INNER JOIN isson s
ON i.sibling=s.mother OR i.sibling=s.father
),
hasniece(name, niece, sibling) AS (
SELECT i1.name,d.name,i1.sibling
FROM issibling i1 INNER JOIN isdaughter d
ON i1.sibling=d.mother OR i1.sibling=d.father
)
SELECT 'F', name, niece AS rel, sibling FROM hasniece UNION
SELECT 'M', name, nephew AS rel, sibling FROM hasnephew
ORDER BY 1,2,3;
aunts + uncles
col1 name rel sibling
---------- ------------ ----------- -------
F Aunt Cousin Uncle1
F Aunt Sis Dad
F Aunt StSis Dad
F Bro Daugtr Me
F Bro Niece Sis
F Dad Cousin Uncle1
F Me Niece Sis
F Sis Daugtr Me
F Uncle1 Sis Dad
F Uncle1 StSis Dad
F Uncle2 Cousin Uncle1
F Uncle2 Sis Dad
F Uncle2 StSis Dad
M Aunt Bro Dad
M Aunt Me Dad
M Bro Son Me
M Me Nephew Bro
M Sis Nephew Bro
M Sis Son Me
M Uncle1 Bro Dad
M Uncle1 Me Dad
M Uncle2 Bro Dad
M Uncle2 Me Dad