SQL Query to get the Waiting Holds From reserves table.

26 Jun 2019

      Hello all,

Could someone please help me in creating the SQL query to get all the holds
in the library for which the book is available,in the library (i.e, no
issue exists for that book)

The reserves table contains some rows for which  itemnumber is Null, and
the waitingdate is Null for every row even if no issue exists for the item.

I came up with the following sql query, but I am not sure if I am right,
can someone please verify my query, or rectify it with the correct query:

      ```SELECT
         borrowers.surname, borrowers.email, borrowers.cardnumber,
items.barcode, biblio.title, reserves.reservedate
      FROM reserves
      LEFT JOIN borrowers USING (borrowernumber)
      LEFT JOIN items USING (itemnumber)
      LEFT JOIN biblio ON (reserves.biblionumber = biblio.biblionumber)
      WHERE
          (reserves.itemnumber IS NOT NULL
          AND NOT EXISTS(SELECT issue_id FROM issues WHERE items.itemnumber
= issues.itemnumber)
          )
          OR
          (reserves.itemnumber IS NULL
          AND EXISTS(
              SELECT itemnumber FROM items i2 WHERE
items.biblionumber=reserves.biblionumber
              AND NOT EXISTS(
                  SELECT issue_id FROM issues WHERE
issues.itemnumber=i2.itemnumber
                  )
              )
          )
```

Thanks in advance
Regards
*Raghav Arora*
Sophomore, M.Sc (Hons) Chemistry BE Electrical and Electronics Engineering
Contact : (+91) 9897597761
Personal Email <raghavarora999@yahoo.in> | University Email
<f20171016@pilani.bits-pilani.ac.in>
LinkedIn <https://www.linkedin.com/in/raghav-arora-9820a648/> |  GitHub
<https://github.com/RAraghavarora/>

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*Birla Institute of Technology and Science, Pilani*
Pilani campus,
Rajasthan-333031

RAGHAV ARORA

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