RDBMS side by side

SQL

Object	Oracle	PostgreSQL
value out-of table	DUAL as virtual table	SELECT without FROM

Transaction

Object	Oracle	PostgreSQL
DDL validate transaction	Yes	No

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Procedural

Object	Oracle	PostgreSQL
Package	X
Named parameter	X	X
access I/O (eg. fs)	X	X (use untrusted)
add languages (eg. C)	X