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Isn't SQL Turing complete? So imo the question of "how expressive is SQL" is really just "how expressive can SQL be with reasonably useful performance".

corpMaverick 9y ago
From what I can understand (barely) The paper tries to determine if some of the new(2003) SQL3 extensions were really needed. From the answers here https://stackoverflow.com/questions/900055/is-sql-or-even-tsql-turing-complete https://stackoverflow.com/questions/900055/is-sql-or-even-ts... It seems that SQL92 was not Turing complete but it became turing complete later on. Possibly by the same extensions added in SQL3.
- MarkusWinand 9y ago
  The mentioned proof is confirming SQL:2003. See also: https://wiki.postgresql.org/wiki/Cyclic_Tag_System https://wiki.postgresql.org/wiki/Cyclic_Tag_System
lmkg 9y ago
I don't think that vanilla SQL defined in older versions of the standard is actually Turing-complete. Most commercial releases included features that made it Turing complete, and my understanding is that the most recent standard includes enough from these features that it's now Turing-complete.
mhd 9y ago
That reminds me of some horrible datbase designs I've seen, where people too enamored with FSMs/petri nets etc. tried to put the "code" into tables…
- Kenji 9y ago
  Sounds like the stuff my code refactoring nightmares are made of. The opposite case is funny too though: I've seen people who fetched and deserialized the entire SQL table and then manually SELECTed by looping over it with a foreach loop and picking the right record =) They even had their own custom logic to do table JOINs. It involved fetching and deserializing both entire tables with SELECT *, of course. Relational calculus at its finest, me gusta.
kafkaesq 9y ago
Isn't SQL Turing complete? Even if it is -- "turing complete" != "expressive". They're rather different beasties, in fact.

corpMaverick 9y ago

From what I can understand (barely) The paper tries to determine if some of the new(2003) SQL3 extensions were really needed. From the answers here https://stackoverflow.com/questions/900055/is-sql-or-even-tsql-turing-complete https://stackoverflow.com/questions/900055/is-sql-or-even-ts... It seems that SQL92 was not Turing complete but it became turing complete later on. Possibly by the same extensions added in SQL3.

MarkusWinand 9y ago
The mentioned proof is confirming SQL:2003. See also: https://wiki.postgresql.org/wiki/Cyclic_Tag_System https://wiki.postgresql.org/wiki/Cyclic_Tag_System

lmkg 9y ago

I don't think that vanilla SQL defined in older versions of the standard is actually Turing-complete. Most commercial releases included features that made it Turing complete, and my understanding is that the most recent standard includes enough from these features that it's now Turing-complete.

mhd 9y ago

That reminds me of some horrible datbase designs I've seen, where people too enamored with FSMs/petri nets etc. tried to put the "code" into tables…

Kenji 9y ago
Sounds like the stuff my code refactoring nightmares are made of. The opposite case is funny too though: I've seen people who fetched and deserialized the entire SQL table and then manually SELECTed by looping over it with a foreach loop and picking the right record =) They even had their own custom logic to do table JOINs. It involved fetching and deserializing both entire tables with SELECT *, of course. Relational calculus at its finest, me gusta.

kafkaesq 9y ago

Isn't SQL Turing complete? Even if it is -- "turing complete" != "expressive". They're rather different beasties, in fact.