Josh Berkus <josh@agliodbs.com> writes:
> UPDATE assignments SET status = -1
> FROM assignments JOIN orders ON assignments.order_usq = orders.usq
> WHERE orders.status = -1;
> However, I get an error of "Relation assignments referenced twice in
> query."
> Now, I can (and have) re-phrase the query so that PostgreSQL will
> accept it. However, I was under the impression that the above was
> standard SQL92. Am I mistaken?
You are mistaken. SQL92 and SQL99 don't allow a FROM clause in UPDATE
at all: they say it's just
<update statement: searched> ::= UPDATE <target table> SET <set clause list>
[ WHERE <search condition> ]
Postgres allows the clause, but treats it as supplying *additional*
table references besides the target table reference. Thus the error.
In other words: you can JOIN, but not against the target table.
regards, tom lane
