Re: pl/sql engine doubt

[Bj�rn Engsig]

PL/SQL can be seen as a stand-alone interpreted language and can as such exist in various environments.  "Various envrionments" does in real life mean the PL/SQL engine is found in both the Oracle server and in the Oracle Forms tool.  If an application needs to execute some PL/SQL it should (at least in principle) be able to execute this in any available environment where the PL/SQL engine is present, in practice, however, this is only the case in the database server and in Oracle Forms (plus probably Oracle Reports, I really don't know, but it's beside the point).  In practical terms, if you are coding forms (plus probably reports), you have PL/SQL available in the tool and in the database server; in all other cases, it's only in the database server.  Whenever PL/SQL needs to execute some SQL statements, it will have to go to the Oracle server; if your PL/SQL happens to already execute there, it is a simple internal context switch inside the server, if your PL/SQL happens to execute in Oracle Forms (or reports), it will have to go over your SQL*Net connection to execute the SQL code.

To confuse things somewhat, PL/SQL actually has a SQL parser; hence, PL/SQL can verify SQL statements during parse without actually talking to the database.  This has some interesting side effects in version 8, where the SQL parser inside  PL/SQL tend to not have adopted all the latest SQL features, i.e. there is valid SQL (in e.g. 8.1.7), that you cannot use in PL/SQL without using dynamic SQL (either DBMS_SQL or native dynamic SQL).

/Bjørn.

sam d wrote:

Hi List,
I was going thru Oracle "PL/SQL User's Guide and
Reference".
http://otn.oracle.com/docs/products/oracle9i/doc_library/release2/appdev.920/a96624/01_oview.htm#962

Paragraphs below (near the "Figure 1-4 PL/SQL Engine"
in the doc) confused me little.

para1 ---
"These two environments are independent. PL/SQL is
bundled with the Oracle server but might be
unavailable in some tools. In either environment, the
PL/SQL engine accepts as input any valid PL/SQL block
or subprogram. Figure 1-4 shows the PL/SQL engine
processing an anonymous block. The engine executes
procedural statements but sends SQL statements to the
SQL Statement Executor in the Oracle server."


para2--
"In the Oracle Database Server:
Application development tools that lack a local PL/SQL
engine must rely on Oracle to process PL/SQL blocks
and subprograms. When it contains the PL/SQL engine,
an Oracle server can process PL/SQL blocks and
subprograms as well as single SQL statements. The
Oracle server passes the blocks and subprograms to its
local PL/SQL engine."


Now my doubt is:
1.In para1 - Does pl/sql engine only processes 
the procedural statements and always passes SQL 
statements to SQL Statement Executor ?

2.In para2 sentence "When it contains ..." says 
Oracle pl/sql engine can process SQL statements.

Statements in both paragraphs seems ambiguous. 
Pls shade some light.

Thanks
Sam


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Bjørn Engsig, Miracle A/S
Member of Oak Table Network
[EMAIL PROTECTED] - http://MiracleAS.dk