I stumbled upon a really attention-grabbing query on Stack Overflow about the right way to use jOOQ’s MULTISET operator to nest a set, after which filter the outcome by whether or not that nested assortment accommodates a worth.
The query is jOOQ particular, however think about, you will have a question that nests collections utilizing JSON in PostgreSQL. Assuming, as all the time, the Sakila database. Now, PostgreSQL doesn’t assist the SQL normal MULTISET operator, however we will use ARRAY, which works nearly the identical approach.
SELECT
f.title,
ARRAY(
SELECT ROW(
a.actor_id,
a.first_name,
a.last_name
)
FROM actor AS a
JOIN film_actor AS fa USING (actor_id)
WHERE fa.film_id = f.film_id
ORDER BY a.actor_id
)
FROM movie AS f
ORDER BY f.title
This produces all movies and their actors as follows (I’ve truncated the arrays for readability functions. You get the purpose):
title |array
---------------------------+--------------------------------------------------------------------------------------
ACADEMY DINOSAUR |{"(1,PENELOPE,GUINESS)","(10,CHRISTIAN,GABLE)","(20,LUCILLE,TRACY)","(30,SANDRA,PECK)"
ACE GOLDFINGER |{"(19,BOB,FAWCETT)","(85,MINNIE,ZELLWEGER)","(90,SEAN,GUINESS)","(160,CHRIS,DEPP)"}
ADAPTATION HOLES |{"(2,NICK,WAHLBERG)","(19,BOB,FAWCETT)","(24,CAMERON,STREEP)","(64,RAY,JOHANSSON)","(1
AFFAIR PREJUDICE |{"(41,JODIE,DEGENERES)","(81,SCARLETT,DAMON)","(88,KENNETH,PESCI)","(147,FAY,WINSLET)"
AFRICAN EGG |{"(51,GARY,PHOENIX)","(59,DUSTIN,TAUTOU)","(103,MATTHEW,LEIGH)","(181,MATTHEW,CARREY)"
AGENT TRUMAN |{"(21,KIRSTEN,PALTROW)","(23,SANDRA,KILMER)","(62,JAYNE,NEESON)","(108,WARREN,NOLTE)",
AIRPLANE SIERRA |{"(99,JIM,MOSTEL)","(133,RICHARD,PENN)","(162,OPRAH,KILMER)","(170,MENA,HOPPER)","(185
AIRPORT POLLOCK |{"(55,FAY,KILMER)","(96,GENE,WILLIS)","(110,SUSAN,DAVIS)","(138,LUCILLE,DEE)"}
ALABAMA DEVIL |{"(10,CHRISTIAN,GABLE)","(22,ELVIS,MARX)","(26,RIP,CRAWFORD)","(53,MENA,TEMPLE)","(68,
Now, the query on Stack Overflow was, the right way to filter this outcome by whether or not the ARRAY (or MULTISET) accommodates a selected worth.
Filtering the ARRAY
We will’t simply add a WHERE clause to the question. Due to the logical order of operations in SQL, the WHERE clause “occurs earlier than” the SELECT clause, so the ARRAY isn’t but obtainable to WHERE. We may, nonetheless, wrap every part in a derived desk and do that, as an alternative:
SELECT *
FROM (
SELECT
f.title,
ARRAY(
SELECT ROW(
a.actor_id,
a.first_name,
a.last_name
)
FROM actor AS a
JOIN film_actor AS fa USING (actor_id)
WHERE fa.film_id = f.film_id
ORDER BY a.actor_id
) AS actors
FROM movie AS f
) AS f
WHERE actors @> ARRAY[(
SELECT ROW(a.actor_id, a.first_name, a.last_name)
FROM actor AS a
WHERE a.actor_id = 1
)]
ORDER BY f.title
Excuse the unwieldy ARRAY @> ARRAY operator. I’m not conscious of a greater method right here, as a result of it’s arduous to unnest a structurally typed RECORD[] array in PostgreSQL, if we don’t use a nominal sort (CREATE TYPE ...). If you realize a greater approach to filter, please let me know within the feedback part. Right here’s a greater model:
SELECT *
FROM (
SELECT
f.title,
ARRAY(
SELECT ROW(
a.actor_id,
a.first_name,
a.last_name
)
FROM actor AS a
JOIN film_actor AS fa USING (actor_id)
WHERE fa.film_id = f.film_id
ORDER BY a.actor_id
) AS actors
FROM movie AS f
) AS f
WHERE EXISTS (
SELECT 1
FROM unnest(actors) AS t (a bigint, b textual content, c textual content)
WHERE a = 1
)
ORDER BY f.title
Anyway, this produces the specified outcome:
title |actors
---------------------+-------------------------------------------------------------------------------------------------
ACADEMY DINOSAUR |{"(1,PENELOPE,GUINESS)","(10,CHRISTIAN,GABLE)","(20,LUCILLE,TRACY)","(30,SANDRA,PECK)","(40,JOHNN
ANACONDA CONFESSIONS |{"(1,PENELOPE,GUINESS)","(4,JENNIFER,DAVIS)","(22,ELVIS,MARX)","(150,JAYNE,NOLTE)","(164,HUMPHREY
ANGELS LIFE |{"(1,PENELOPE,GUINESS)","(4,JENNIFER,DAVIS)","(7,GRACE,MOSTEL)","(47,JULIA,BARRYMORE)","(91,CHRIS
BULWORTH COMMANDMENTS|{"(1,PENELOPE,GUINESS)","(65,ANGELA,HUDSON)","(124,SCARLETT,BENING)","(173,ALAN,DREYFUSS)"}
CHEAPER CLYDE |{"(1,PENELOPE,GUINESS)","(20,LUCILLE,TRACY)"}
COLOR PHILADELPHIA |{"(1,PENELOPE,GUINESS)","(106,GROUCHO,DUNST)","(122,SALMA,NOLTE)","(129,DARYL,CRAWFORD)","(163,CH
ELEPHANT TROJAN |{"(1,PENELOPE,GUINESS)","(24,CAMERON,STREEP)","(37,VAL,BOLGER)","(107,GINA,DEGENERES)","(115,HARR
GLEAMING JAWBREAKER |{"(1,PENELOPE,GUINESS)","(66,MARY,TANDY)","(125,ALBERT,NOLTE)","(143,RIVER,DEAN)","(155,IAN,TANDY
Now, all the outcomes are assured to be movies during which 'PENELOPE GUINESS' was an ACTOR. However is there a greater resolution?
Utilizing ARRAY_AGG as an alternative
Nonetheless, in native PostgreSQL, it will be higher (on this case) to make use of ARRAY_AGG, I feel:
SELECT
f.title,
ARRAY_AGG(ROW(
a.actor_id,
a.first_name,
a.last_name
) ORDER BY a.actor_id) AS actors
FROM movie AS f
JOIN film_actor AS fa USING (film_id)
JOIN actor AS a USING (actor_id)
GROUP BY f.title
HAVING bool_or(true) FILTER (WHERE a.actor_id = 1)
ORDER BY f.title
This produces the very same outcome:
title |actors
---------------------+------------------------------------------------------------------------------------------------
ACADEMY DINOSAUR |{"(1,PENELOPE,GUINESS)","(10,CHRISTIAN,GABLE)","(20,LUCILLE,TRACY)","(30,SANDRA,PECK)","(40,JOHN
ANACONDA CONFESSIONS |{"(1,PENELOPE,GUINESS)","(4,JENNIFER,DAVIS)","(22,ELVIS,MARX)","(150,JAYNE,NOLTE)","(164,HUMPHRE
ANGELS LIFE |{"(1,PENELOPE,GUINESS)","(4,JENNIFER,DAVIS)","(7,GRACE,MOSTEL)","(47,JULIA,BARRYMORE)","(91,CHRI
BULWORTH COMMANDMENTS|{"(1,PENELOPE,GUINESS)","(65,ANGELA,HUDSON)","(124,SCARLETT,BENING)","(173,ALAN,DREYFUSS)"}
CHEAPER CLYDE |{"(1,PENELOPE,GUINESS)","(20,LUCILLE,TRACY)"}
COLOR PHILADELPHIA |{"(1,PENELOPE,GUINESS)","(106,GROUCHO,DUNST)","(122,SALMA,NOLTE)","(129,DARYL,CRAWFORD)","(163,C
ELEPHANT TROJAN |{"(1,PENELOPE,GUINESS)","(24,CAMERON,STREEP)","(37,VAL,BOLGER)","(107,GINA,DEGENERES)","(115,HAR
GLEAMING JAWBREAKER |{"(1,PENELOPE,GUINESS)","(66,MARY,TANDY)","(125,ALBERT,NOLTE)","(143,RIVER,DEAN)","(155,IAN,TAND
How does it work?
- We’re grouping by
FILMand mixture the contents per movie right into a nested assortment. - We will now use
HAVINGto filter on teams. BOOL_OR(TRUE)isTRUEas quickly because theGROUPis non-emptyFILTER (WHERE a.actor_id = 1)was that filter standards, which we place within the group
So, the HAVING predicate is TRUE if there’s at the least one ACTOR_ID = 1, or NULL in any other case, which has the identical impact as FALSE. In case you’re a purist, wrap the predicate in COALESCE(BOOL_OR(...), FALSE)
Intelligent or neat, or a little bit of each?
Doing this with jOOQ
Right here’s the jOOQ model, that works on any RDBMS that helps MULTISET_AGG (ARRAY_AGG emulation remains to be pending):
ctx.choose(
FILM_ACTOR.movie().TITLE,
multisetAgg(
FILM_ACTOR.actor().ACTOR_ID,
FILM_ACTOR.actor().FIRST_NAME,
FILM_ACTOR.actor().LAST_NAME))
.from(FILM_ACTOR)
.groupBy(FILM_ACTOR.movie().TITLE)
.having(boolOr(trueCondition())
.filterWhere(FILM_ACTOR.actor().ACTOR_ID.eq(1)))
.orderBy(FILM_ACTOR.movie().TITLE)
.fetch();
Whereas the highly effective MULTISET worth constructor will get many of the fame with jOOQ customers, let’s not overlook there’s additionally a barely much less highly effective, however often actually helpful MULTISET_AGG mixture perform, which can be utilized for aggregations or as a window perform!
