Technitribe

interesting problems (and a few solutions, too)

Technitribe
  • About the Authors
  • Log In
  • Log Out
  • Lost Password
  • Register
  • Reset Password
    • 19 Jan 2017

      References in a sub-select

      Written by Alex Wood

      Have you ever had a sub-select where you really needed to reference a value in the outer query? I know I have! The naive way would be to run the outer query and then loop over the results running the inner query on each one. Luckily, there’s a better way. The Correlated subquery. Check it out! The example given is 

      SELECT employee_number, name
  FROM employees AS Bob
  WHERE salary > (
    SELECT AVG(salary)
      FROM employees
      WHERE department = Bob.department);

      See how the sub-select references the outer query? It’s SQL magic.

      • Tags »

    Leave a Reply Cancel reply

    Your email address will not be published. Required fields are marked *

    • The Authors

    • Virtual Disk Guide

      Interested in virtualization? Do QCOWs rule your filesystem? Are you a libvirt or KVM+QEMU wizard? I wrote a book about virtual disk management. Check out the The Linux Sysadmin's Guide to Virtual Disks online for free at ScribesGuides.com.

      Consider supporting the author by purchasing a hard copy of the first edition for just $10.00 on Lulu.com.

    • bitmath

      bitmath is a Python library for dealing with file size units (GiB's, kB's, etc) in a sane way. bitmath supports arithmetic, rich comparison, conversion, automatic best human-readable representation, and many other utility functions. Read some examples on the docs site or check out the source on GitHub.

    • latest posts

      • Querying block device sizes in Python on Linux and Mac OS X February 4, 2023
      • Using jq to filter an array of objects from JSON September 9, 2019
      • Two Year Break — And we’re back! November 16, 2018

    • tags

      bitmath blog conference css dblatex DNS DocBook eclipse Emacs Erlang Fedora fedora 22 filter GNU Screen Haiku Introduction java jboss LCSEE Linux locale locales fix slicehost ubuntu Macports module nist nXML-Mode opengl open source OS X package packaging pki prefix units presentation project pypi Python scholarship si summit Tutorial ubuntu xcode XML XMPP

    • h4ck teh world

      tbielawatbielawa
      • Watch
        spotDL/spotify-downloader
        March 27, 2023 - 2:52 pm UTC
      • Watch
        exaloop/codon
        March 19, 2023 - 3:05 pm UTC
      • Issue Comment
        hashicorp/vault
        March 2, 2023 - 2:40 pm UTC
      • Issue Comment
        bitmath
        February 15, 2023 - 10:26 pm UTC
      • Issue Comment
        bitmath
        February 15, 2023 - 10:25 pm UTC

Creative Commons License
Technitribe by Tim Bielawa is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.