MySQL complicated query | extracting a phrase from table of words - mysql

Question

I'm working through MySQL connector in python on a project where I'm analyzing books.
I would gladly accept any help with my issue (explained below).
The relevant DB structures:
each Word, in each book, has its own word_id(primary key) and text.
each Word_instance has word_id, word_serial, offset in line, sentence number and so on...
the entity Word_instance's word_serial is its offset from the beginning of the book.
each Phrase has its own id and text.
each Phrase_word has phrase_id and word_id(from above).
Right now, I'm trying to figure out how to build a query that will locate a phrase from the user in the database.
Words are a part of a phrase if they have consecutive word_serial and are in the same sentence.
so far I've managed to build the following mess of a query:
select book_id
, word_txt
, word_serial
, sentence_serial
, ROW_NUMBER() Over (partition by sentence_serial, book_id) as encounter_num
from word
join word_instance
on word.word_id = word_instance.word_id
join word_in_phrase
on word.word_id = word_in_phrase.word_id
where phrase_id = %s
order
by book_id
, sentence_serial
, word_serial
In the following table image is the result set of said query.
let's say the user has entered the phrase: "I believe in cause".
in that case I would need to extract word_serial = 562, as it is the beginning said phrase.
can I accomplish such a task without extracting row by row and assessing whether the current row is part of the phrase and in the correct order?
In fact, there are way to many rows to examine outside of SQL to consider that a possibility.
I will appreciate your help immensely, as I'm stuck on this issue for far too long...
As requested, I'm uploading images of relevant DB entities:
Word_in_phrase entity
Word_instance entity
word entity

Answer 1

This probably isn't the most efficient way of writing this, but I think it works in principle and you could tinker with it as you wanted. Note that I assumed phrases can't cross sentence boundaries (wi2.sentence_serial = wi1.sentence_serial) and I've assumed a column word_in_phrase.order_id exists that starts at 0 and increases by 1 for each word. I'm also assuming word_id increases by 1 each row. (You could make those assumptions true by using CTEs where that is true instead of the real tables).
with (
SELECT *
FROM word_in_phrase
WHERE phrase_id = %s
) as phrase
select book_id
, word_txt
, word_serial
, sentence_serial
from word
join word_instance wi1
on word.word_id = word_instance.word_id
where (SELECT COUNT(*) FROM phrase) = (SELECT COUNT(*) FROM word_instance wi2 INNER JOIN phrase on wi2.word_id = phrase.word_id WHERE wi2.book_id = wi1.book_id and wi2.sentence_serial = wi1.sentence_serial and wi2.word_id = wi1.word_id + phrase.order_id)
order
by book_id
, sentence_serial
, word_serial
Alternatively, you might prefer something like
with (
SELECT *
FROM word_in_phrase
WHERE phrase_id = %s
) as phrase
select wi1.book_id
, word_txt
, wi1.word_serial
, wi1.sentence_serial
from word
join word_instance wi1
on word.word_id = word_instance.word_id
inner join word_instance wi2
on wi2.book_id = wi1.book_id and wi2.sentence_serial = wi1.sentence_serial
INNER JOIN phrase
on wi2.word_id = phrase.word_id
WHERE wi2.word_id = wi1.word_id + phrase.order_id
GROUP BY
wi1.book_id
, word_txt
, wi1.word_serial
, wi1.sentence_serial
HAVING COUNT(*) = (SELECT COUNT(*) FROM phrase)