Correct answers are A and E. 

 

There are many RDBMS products, which have very similar functions, but there are slight differences in these functions depending on the RDBMS product. 

A stored procedure is a function supported by many RDBMS, and it stores a series of instructions as a procedure in the RDBMS. 

Depending on whether the procedure returns a value, it is classified as a function (returning a value) and a procedure (not returning a value). 

PostgreSQL allows you to create functions using the language PL / pgSQL, but because it does not support procedures, it will be implemented as a function. 

A database trigger is a program that is automatically executed for an event on a table, specifically, it is started before or after data operations such as INSERT / UPDATE / DELETE. 

PostgreSQL has supported triggers from version 6.2. 

Sequences are mainly used in columns requiring unique values such as ID columns. PostgreSQL allows you to define a sequence with the CREATE SEQUENCE statement. 

A synonym is a function that makes it possible to access aliases for tables and views, and depending on the type of RDBMS, it is sometimes called an alias. 

Since PostgreSQL 9.0 does not support synonyms (aliases), it can be realized using views and rules. 

Just because a specific function is not supported does not mean that the function can not be used at all. 

In many cases there are alternatives.