The difference is from as in pl / sql

as and is similar to each other, but there is a slight difference:

• They are synonymous when creating procedures or packages.

• They are different when creating a cursor or table.

For example, it will work:

 cursor test_cursor is select * from emp; 

... and this is no longer:

 cursor test_cursor as select * from emp; 

Similarly with tables - this code works:

 create table test_table as select sysdate from dual 

And this will already give the error "missing or invalid option":

 create table test_table is select sysdate from dual 

_{A source.}

There is no difference. The keywords is and as are synonymous, supplied in order to make the code more readable. For example:

 FUNCTION f IS ... CREATE VIEW v AS SELECT ... 

Yes, only semantic difference. I usually use as when creating packages

create ... as - Create as ...

and is when defining procedures and functions

procedure ... is - Procedure - is ...