How to decide if an ORM is decent? Just try to replicate every SQL query from nodejs/sequelize/raw/many_to_many.js on PostgreSQL and SQLite.
There is only a very finite number of possible reasonable queries on a two table many to many relationship with a join table. A decent ORM has to be able to do them all.
If it can do all those queries, then the ORM can actually do a good subset of SQL and is decent. If not, it can't, and this will make you suffer. E.g. Sequelize v5 is such an ORM that makes you suffer.
The next thing to check are transactions.
Basically, all of those come up if you try to implement a blog hello world world such as gothinkster/realworld correctly, i.e. without unnecessary inefficiencies due to your ORM on top of underlying SQL, and dealing with concurrency.
github.com/mdawsonuk/LevelDBDumper/tree/e750a27ff58443ecc410b5c16abbdc539d617387#installation worked on Ubuntu 23.10 Annoying installation, but worked: github.com/mdawsonuk/LevelDBDumper/issues/13
List databases:
echo 'show dbs' | mongoShow all data from one of the collections: stackoverflow.com/questions/24985684/mongodb-show-all-contents-from-all-collections
echo 'db.collectionName.find()' | mongo mydbTested as of Ubuntu 20.04, there is no Mongo package available by default due to their change to Server Side Public License, which Debian opposed. Therefore, you have to add their custom PPA as mentioned at: docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
Sequelize is used minimally, just to feed raw queries in transparently to any underlying database, and get minimally parsed results out for us, which we then assert with standard JavaScript. The queries themselves are all written by hand.
By default the examples run on SQLite. Just like the examples from sequelize example, you can set the database at runtime as:
./index.jsor./index.js l: SQLite./index.js p: PostgreSQL. You must manually create a database calledtmpand ensure that peer authentication works for it
Here we list only examples which we believe are standard SQL, and should therefore work across different SQL implementations:
- nodejs/sequelize/raw/index.js: basic hello world to demonstrate the setup and very simple functionality
- nodejs/sequelize/raw/many_to_many.js: illustrates many-to-many relations with JOIN. Contains:
- SQL transaction examples:
- nodejs/sequelize/raw/commit_error.js: stackoverflow.com/questions/27245101/why-should-we-use-rollback-in-sql-explicitly/27245234#27245234 and stackoverflow.com/questions/48277519/how-to-use-commit-and-rollback-in-a-postgresql-function/48277708#48277708 suggest that on PostgreSQL, once something fails inside a transaction, all queries in the current transaction are ignored, and
COMMITsimply does aROLLBACK. Let's check. Yup, true for Postgres, but false for SQLite, SQLite just happily runs anything it can, you really needROLLBACKfor it. - SQL isolation level example
- nodejs/sequelize/raw/commit_error.js: stackoverflow.com/questions/27245101/why-should-we-use-rollback-in-sql-explicitly/27245234#27245234 and stackoverflow.com/questions/48277519/how-to-use-commit-and-rollback-in-a-postgresql-function/48277708#48277708 suggest that on PostgreSQL, once something fails inside a transaction, all queries in the current transaction are ignored, and
- GROUP BY and SQL aggregate functions:
- nodejs/sequelize/raw/group_by_extra_column.js: let's see if it blows up or not on different DB systems,
sqlite3Node.js package allows it:- github.com/sequelize/sequelize/issues/5481#issuecomment-964387232
- dba.stackexchange.com/questions/141594/how-select-column-does-not-list-in-group-by-clause/141600 says that it was allowed in SQL:1999 when there are no ambiguities due to constraints, e.g. when grouping by unique columns
- github.com/postgres/postgres/blob/REL_13_5/src/test/regress/sql/functional_deps.sql#L27 shows that PostgreSQL wants it to work for
UNIQUE NOT NULL, but they just haven't implemented it as of 13.5, where it only works if you group byPRIMARY KEY - dba.stackexchange.com/questions/158015/why-can-i-select-all-fields-when-grouping-by-primary-key-but-not-when-grouping-b also says that
UNIQUE NOT NULLdoesn't work. Dan Lenski then points to a rationale mailing list thread.
- nodejs/sequelize/raw/group_by_max_full_row.js: here we try to get the full row of each group at which a given column reaches the max of the group
- Postgres: has
SELECT DISCINTCT ONwhich works perfectly if you only want one row in case of multiple rows attaining the max.ONis an extension to the standard unfortunately: www.postgresql.org/docs/9.3/sql-select.html#SQL-DISTINCT Docs specify that it always respectsORDER BYwhen selecting the row.- stackoverflow.com/questions/586781/postgresql-fetch-the-row-which-has-the-max-value-for-a-column asks it without the multiple matches use case
- stackoverflow.com/questions/586781/postgresql-fetch-the-rows-which-have-the-max-value-for-a-column-in-each-group/587209#587209 also present in simpler form at stackoverflow.com/questions/121387/fetch-the-rows-which-have-the-max-value-for-a-column-for-each-distinct-value-of/123481#123481 gives a very nice OUTER JOIN only solution! Incredible, very elegant.
- dba.stackexchange.com/questions/171938/get-only-rows-with-max-group-value asks specifically the case of multiple matches to the max
- stackoverflow.com/questions/586781/postgresql-fetch-the-row-which-has-the-max-value-for-a-column asks it without the multiple matches use case
- SQLite:
- stackoverflow.com/questions/48326957/row-with-max-value-per-group-sqlite
- stackoverflow.com/questions/48326957/row-with-max-value-per-group-sqlite/48328243#48328243 teaches us that in SQLite min and max are magic and guarantee that the matching row is returned
- stackoverflow.com/questions/48326957/row-with-max-value-per-group-sqlite/72996649#72996649 Ciro Santilli uses the magic of
ROW_NUMBER
- stackoverflow.com/questions/17277152/sqlite-select-distinct-of-one-column-and-get-the-others/71924314#71924314 get any full row without specifying which, we teach how to specify
- code.djangoproject.com/ticket/22696 WONTFIXed
DISTINCT ON- stackoverflow.com/questions/50846722/what-is-the-difference-between-postgres-distinct-vs-distinct-on/72997494#72997494
DISTINCTvsDISTINCT ON, somewhat related question
- stackoverflow.com/questions/50846722/what-is-the-difference-between-postgres-distinct-vs-distinct-on/72997494#72997494
- stackoverflow.com/questions/48326957/row-with-max-value-per-group-sqlite
- stackoverflow.com/questions/5803032/group-by-to-return-entire-row asks how to take the top N with distinct after order limit. I don't know how to do it in Postgres
- Postgres: has
- nodejs/sequelize/raw/most_frequent.js: illustrates a few variants of findind the mode, including across GROUP
- nodejs/sequelize/raw/group_by_max_n.js: get the top N in each group
- nodejs/sequelize/raw/group_by_extra_column.js: let's see if it blows up or not on different DB systems,
- order results in the same order as
IN: - LIMIT by a running total: TODO links
Login without password: askubuntu.com/questions/915585/how-to-login-mysql-shell-when-mysql-have-no-passwordworks on Ubuntu 20.10.
sudo mysqlCreate user for further logins without
sudo askubuntu.com/questions/915585/how-to-login-mysql-shell-when-mysql-have-no-password/1325689#1325689:sudo mysql -e "CREATE USER $USER"Run command from CLI stackoverflow.com/questions/1602904/how-do-you-run-a-single-query-through-mysql-from-the-command-line
mysql -e 'SHOW DATABASES'Create test user with password:and login as that user:Login with password given on the command line:The
sudo mysql -e 'CREATE USER user0 IDENTIFIED WITH mysql_native_password BY "a"'
sudo mysql -e 'GRANT ALL PRIVILEGES ON database_name.* TO "user0"'mysql -u user0 -pmysql -u user0 -pmypasswordIDENTIFIED WITH mysql_native_password part is to overcome "Client does not support authentication protocol requested by server" when connecting from Node.js.List users:
sudo mysql -e 'SELECT * FROM mysql.user'View permissions for each user on each DB: serverfault.com/questions/263868/how-to-know-all-the-users-that-can-access-a-database-mysql
sudo mysql -e 'SELECT * FROM mysql.db'List databases:
sudo mysql -e 'SHOW DATABASES'Create database:
sudo mysql -e 'CREATE DATABASE mydb0'Destroy database:
sudo mysql -e 'DROP DATABASE mydb0' Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 3. Visual Studio Code extension installation.
Figure 4. Visual Studio Code extension tree navigation.
Figure 5. Web editor. You can also edit articles on the Web editor without installing anything locally.Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.Video 4. OurBigBook Visual Studio Code extension editing and navigation demo. Source. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact