CTE stands for Common Table Expressions in SQL. They are temporary result sets defined within a single query using the WITH clause, acting like named subqueries to improve readability and structure.
As someone who is not much of a sports person, now I was wondering what CTE means in sports.
Seems to be this:
> Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease […]
> Evidence indicates that repetitive concussive and subconcussive blows to the head cause CTE. In particular, it is associated with contact sports such as boxing, American football, Australian rules football, wrestling, mixed martial arts, ice hockey, rugby, and association football.
The NFL in the US has famously gone to great lengths to downplay the impact of CTE on current and retired players. And there have been several famous players who literally lost their minds as they aged, and we now know that was due to CTE. Something like 90% of ex-NFLers have it. The number is still really bad for collegiate players. And even high school players are at risk.
Yeah - Muhammad Ali is the most famous victim (or at least likely victim, I don’t think he was officially diagnosed with CTE as it wasn’t well understood back then). In the UK, it’s gradually becoming recognised as a serious problem in rugby.
I assumed the C stood for Concussion. Wrong but also partly right!
I was thinking "Compile Time Execution" like Rust's const, C++ consteval functions, Zig's comptime, that sort of thing. So the good/ bad made more sense but I was still on the wrong track, yeah a definition was appropriate.
i appreciate the way you took the feedback. i saw the domain name and immediately knew the content and context. the article did not disappoint. i come from a heavy mssql background with some postgres sprinkled in, but my current company is migrating our mssql fleet to pg and it’s nice to have a technical foundation and article to be able to truly understand and pass the differences and similarities then how the two platforms handle workload. Traditionally it’s just been multiple sides, mercilessly criticizing each other for their deficiencies, but each platform has its own strengths and its own gaps. I’m excited to be a part of this migration, and I appreciate technical articles such as this that help me articulate the broader challenges to both our executive level levels, and our developers.
edit: syntax. voice to text was liberal with the comma abuse
I read the article before the abbreviate definition inclusion as its very opening. I had never met the abbreviation before.
It'd be quite surprising the WITH statement in top a query to be the first feature to learn/use past basic SQL. Is it personal experience in some industry?
Eh, almost every link on the homepage has an initialism or acronym in the title, and roughly none of them are actually defining the term they're using. Indeed, not to point fingers, your own submissions make the same mistake.
Sure, yes, OP should (and now has) defined the term. But at the same time it's reasonable to expect that someone reading a blog post on BoringSQL.com would already know the term just as much as we could expect people interested in Clojure would know what a REPL is.
Your comment could have been more helpful without the first sentence. SAME content, same correction, less superiority: "CTE is an overloaded term, in this article ......"
This is a valuable comment, don't ruin it with sarcasm and rudeness.
I mostly use CTEs for organization these days, and in rare cases to express queries which cannot be written without them.
These days I often write queries like this (especially when doing exploratory ad hoc queries, but also in apps) even when it's not necessary to use a CTE:
WITH
a AS (
SELECT ... FROM ... WHERE ... etc.
)
SELECT * FROM a
The first CTE query defines the input, and the main query just reads from it. Subsequent subqueries invoke steps on that input to group, filter, join, and so on.
This has a bunch of nice benefits. For example, it allows me to add steps incrementally, and to "comment out" a step I can simply change the next step's input to read from the preceding step. Each step can be read and understood in isolation.
I work a lot with Postgres, ClickHouse, and SQLite, and generally find that the database inlines and optimizes CTEs, and challenges mostly concern performance traps (like IN or EXISTS) that allly to non-CTE situations as well.
I've always thought of CTEs as a code organisation tool, not an optimisation tool. The fact the some rdbms treats them as an optimisation fence was a bug, not a feature.
To the author of the article. This was a really nice and educating read. You made me finally understand recursive CTEs, the org chart was a really good example. Thank you.
> Recursive CTEs use an iterative working-table mechanism. Despite the name, they aren't truly recursive. PostgreSQL doesn't "call itself" by creating a nested stack of unfinished queries.
If you want something that is more like actual recursion (I.e., depth-first), Oracle has CONNECT BY which does not require the same kind of tracking. It also comes with extra features to help with cycle detection, stack depth reflection, etc.
If your problem is aligned with the DFS model, the oracle technique can run circles around recursive CTEs. Anything with a deep hierarchy and early termination conditions is a compelling candidate.
Great article, I always like to structure my queries with CTEs and I was (wrongly) assuming it all gets inlined at the end.
Sometimes it also gets complicated since these intermediate results can't be easily seen in a SQL editor. I was working on a UI to parse CTE queries and then execute them step by step to show the results of all the CTEs for easier understanding of the query (as part of this project https://github.com/sqg-dev/sqg/)
Sometimes easy performance trick is to split the CTE to separate queries, put the results to unlogged temporary tables and add whatever indexes the next step needs.
Obviously makes only sense for stuff like analytical queries that are not running constantly.
Not to sound like a broken record, but I need to echo what many other replies have already said: great article.
Embarassingly, despite thinking of myself as pretty knowledgeable with SQL, I had no idea you could nest DML statements inside a CTE. I always assumed/used DML statements as the final statement after a CTE was defined. I'm not sure if or when I might use this in the future, but it's neat to learn something new (and to be humbled at the same time).
45 comments
CTE stands for Common Table Expressions in SQL. They are temporary result sets defined within a single query using the WITH clause, acting like named subqueries to improve readability and structure.
I was morbidly curious what a "good CTE" could possibly be...
Seems to be this:
> Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease […]
> Evidence indicates that repetitive concussive and subconcussive blows to the head cause CTE. In particular, it is associated with contact sports such as boxing, American football, Australian rules football, wrestling, mixed martial arts, ice hockey, rugby, and association football.
https://en.wikipedia.org/wiki/Chronic_traumatic_encephalopat...
The NFL in the US has famously gone to great lengths to downplay the impact of CTE on current and retired players. And there have been several famous players who literally lost their minds as they aged, and we now know that was due to CTE. Something like 90% of ex-NFLers have it. The number is still really bad for collegiate players. And even high school players are at risk.
It was to the point that Will Smith starred in a movie about it. https://en.wikipedia.org/wiki/Concussion_(2015_film)
I assumed the C stood for Concussion. Wrong but also partly right!
edit: syntax. voice to text was liberal with the comma abuse
It'd be quite surprising the WITH statement in top a query to be the first feature to learn/use past basic SQL. Is it personal experience in some industry?
Sure, yes, OP should (and now has) defined the term. But at the same time it's reasonable to expect that someone reading a blog post on BoringSQL.com would already know the term just as much as we could expect people interested in Clojure would know what a REPL is.
This is a valuable comment, don't ruin it with sarcasm and rudeness.
These days I often write queries like this (especially when doing exploratory ad hoc queries, but also in apps) even when it's not necessary to use a CTE:
The first CTE query defines the input, and the main query just reads from it. Subsequent subqueries invoke steps on that input to group, filter, join, and so on.This has a bunch of nice benefits. For example, it allows me to add steps incrementally, and to "comment out" a step I can simply change the next step's input to read from the preceding step. Each step can be read and understood in isolation.
I work a lot with Postgres, ClickHouse, and SQLite, and generally find that the database inlines and optimizes CTEs, and challenges mostly concern performance traps (like IN or EXISTS) that allly to non-CTE situations as well.
Regarding recursive CTEs, you might be interested in how DuckDb evolved them with USING KEY: https://duckdb.org/2025/05/23/using-key
> Recursive CTEs use an iterative working-table mechanism. Despite the name, they aren't truly recursive. PostgreSQL doesn't "call itself" by creating a nested stack of unfinished queries.
If you want something that is more like actual recursion (I.e., depth-first), Oracle has CONNECT BY which does not require the same kind of tracking. It also comes with extra features to help with cycle detection, stack depth reflection, etc.
If your problem is aligned with the DFS model, the oracle technique can run circles around recursive CTEs. Anything with a deep hierarchy and early termination conditions is a compelling candidate.
Obviously makes only sense for stuff like analytical queries that are not running constantly.
I just rewrote all queries with claude code and next day and compute decreased to 1/5th.
Embarassingly, despite thinking of myself as pretty knowledgeable with SQL, I had no idea you could nest DML statements inside a CTE. I always assumed/used DML statements as the final statement after a CTE was defined. I'm not sure if or when I might use this in the future, but it's neat to learn something new (and to be humbled at the same time).
I'll write some nice clean CTEs and then have to refactor it to temp tables due to the lack of materialization.