LeetCode Hard SQL | Dataford Interview Questions

KPIT's engineering knowledge search surface stores indexed text and a required set of equal-length keywords. Write a PostgreSQL query that finds every zero-based character position where the text contains all required keywords exactly once, in any order and including duplicate keyword requirements.

Requirements

Return case_id and the zero-based start_position for every valid match.
Treat the required keywords as a multiset, so duplicate words must occur the required number of times.
Require the matching substring to contain exactly word_count * word_length characters.
Return results ordered by case_id and start_position.
Ignore cases with no usable keyword rows or a NULL search text.

All keywords within a case have the same length.

Schema

search_cases

Column	Type	Description
case_idPK	INT	Search case identifier
search_text	TEXT	Text scanned for concatenated keywords
case_label	VARCHAR(80)	Short description of the search case

required_words

Column	Type	Description
word_idPK	INT	Required-word identifier
case_id	INT	References search_cases.case_id
word_position	INT	Position in the input requirement list
word_text	VARCHAR(40)	Keyword that must occur in the candidate substring

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Problem