Here is a summary of his seven “golden rules” that will help you write better code:

1. Don’t repeat anything.
2. Hide everything.
3. Don’t take shortcuts.
4. Embrace standards.
5. Build on a foundation.
6. Never lose information.
7. Don’t write code alone.

Agreed with all. I would also add an eighth one: Understand your data.

What would you add?

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Let’s execute this simple anonymous PL/SQL block:

eddie@db11gr2> DECLARE
  2    l_string VARCHAR2 (4000);
  3    l_rc sys_refcursor;
  4  BEGIN
  5    l_string := RPAD (' ', 4000);
  6    OPEN l_rc FOR 'select :1 from dual' USING l_string;
  7    EXECUTE immediate 'select :1 from user_objects where rownum = 1'
  8      INTO l_string USING l_string;
  9  END;
 10  /

PL/SQL procedure successfully completed.

The EXECUTE IMMEDIATE and OPEN FOR statements are used with the USING clause. USING supplies a bind argument for the SQL string. In this example the value of the bind argument is a 4,000 character string.

Now, let’s pass a string greater than 4,000 characters to the OPEN FOR statement:

eddie@db11gr2> DECLARE
  2    l_string VARCHAR2 (4001);
  3    l_rc sys_refcursor;
  4  BEGIN
  5    l_string := RPAD (' ', 4001);
  6    OPEN l_rc FOR 'select :1 from dual' USING l_string;
  7  END;
  8  /
DECLARE
*
ERROR at line 1:
ORA-01460: unimplemented or unreasonable conversion requested
ORA-06512: at line 6

Oops, got an error. Let’s also try the EXECUTE IMMEDIATE statement with a string greater than 4,000 characters:

eddie@db11gr2> DECLARE
  2    l_string VARCHAR2 (4001);
  3  BEGIN
  4    l_string := RPAD (' ', 4001);
  5    EXECUTE immediate 'select :1 from user_objects where rownum = 1'
  6      INTO l_string USING l_string;
  7  END;
  8  /
DECLARE
*
ERROR at line 1:
ORA-01460: unimplemented or unreasonable conversion requested
ORA-06512: at line 5

Got the same error: “ORA-01460: unimplemented or unreasonable conversion requested”.

How about if we pass a NULL:

eddie@db11gr2> DECLARE
  2    l_rc sys_refcursor;
  3  BEGIN
  4    OPEN l_rc FOR 'select :1 from dual' USING NULL;
  5  END;
  6  /
  OPEN l_rc FOR 'select :1 from dual' USING NULL;
                                            *
ERROR at line 4:
ORA-06550: line 4, column 45:
PLS-00457: expressions have to be of SQL types
ORA-06550: line 4, column 3:

In this case we get “PLS-00457: expressions have to be of SQL types”.

Well, there is a restriction on what values you can bind: When binding values to dynamic SQL, only SQL datatypes are supported. You can bind strings, numbers, dates, collections, LOBs, XML documents… However, you cannot bind values having a PL/SQL specific datatype such as Booleans, associative arrays and varchar2 values greater than 4000.

Make sure you keep the above restriction in mind when you use the EXECUTE IMMEDIATE … USING and OPEN FOR … USING statements.

Source and resources:

• EXECUTE IMMEDIATE Statement
• Unsupported Data Type in Native Dynamic SQL
• OPEN FOR Statement
• Discussions about the ORA-01460 error

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• More on Generating Strings
• CASE gotcha in Oracle 8i
• Here’s a Quick Way to Get the Line Number in PL/SQL

What is the output of this PL/SQL block?

eddie@db11gr2> DECLARE
  2     aname varchar2 (5);
  3  BEGIN
  4     DECLARE
  5        aname varchar2 (5) := 'Big String';
  6     BEGIN
  7        DBMS_OUTPUT.put_line (aname);
  8     EXCEPTION
  9        WHEN VALUE_ERROR
 10        THEN
 11           DBMS_OUTPUT.put_line ('Inner block');
 12     END;
 13     DBMS_OUTPUT.put_line ('What error');
 14  EXCEPTION
 15     WHEN VALUE_ERROR
 16     THEN
 17        DBMS_OUTPUT.put_line ('Outer block');
 18  END;
 19  /

Instead of telling you what the answer is, I will point you to the documentation:

In declarations, faulty initialization expressions can raise exceptions, but exception handlers cannot handle them… Handlers in the current block cannot catch the raised exception because an exception raised in a declaration propagates immediately to the enclosing block.

Even though I selected the wrong choice when I took the quiz, adding the above fact to my PL/SQL knowledge and sharing it with you is a big win for me.

By the way, should we consider initializing variables in the declaration section a bad practice?

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• How to find where an error was raised in PL/SQL
• Little known way to get the error message in PL/SQL
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In this video interview with ZDNet.com.au, Kyte explains how many questions he receives equate to “my car won’t start”. “I’m going to do it to you — my car won’t start, why? Give me the solution. I’m not going to tell you what errors I see on the dashboard; I’m not going to tell you if I filled the car up with gas recently; I’m not going to tell you if it’s making a noise or not making a noise; but my car won’t start, why not? There’s insufficient data to even begin to answer a question like that.” Kyte also explains how the internet has changed how questions are asked, and how he doesn’t reply with RTFM.

via How developers should ask for help: Blogs – Null Pointer – ZDNet Australia (via)

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Oracle Metalink (now known as “My Oracle Support” ) has over 300 scripts available. Log on to Metalink and then navigiate to:

Top of page – KNOWLEDGE – TOOLS AND TRAINING – DIAGNOSTIC TOOLS

There’s a LOT of stuff available in diagnostic tools. Take advantage of it!

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1. The best times to publish a post are 7am PST and 6pm EST.
2. The best days to publish a post are Tuesday, Thursday and Saturday.
3. Change the word “Category” to “Topic” to increase page views.
4. Display the publishing date at the bottom of the post.
5. Add the number of minutes it takes to read the post. Normally, it’s 250 words per minute.
6. A post should be about one, and only one topic.
7. Write about what you are passionate about.
8. Use tools such as Evernote, slinkset.com and Twitter to gather writing material and poll for ideas.
9. Use Google Keyword Tool to increase your Google juice.
10. Use Flickr’s advanced search to find interesting Creative Commons photos to use in posts.

Of course the above tips worked for Tim but they may or may not work for you and me.

Here is Tim’s full 50 minute presentation:

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But, what about WHEN OTHERS THEN RAISE?

I have known PL/SQL developers who follow a “standard” of adding:

EXCEPTION
   WHEN OTHERS
   THEN
      RAISE;
END;

to every PL/SQL block. The reasoning behind this practice, as explained to me:

• There is no harm in adding it
• It makes maintenance easier
• Used as a placeholder for additional error handling when needed
• There is no overhead executing it

When asked if he was joking when he added “when others then raise;” Shoblock replied:

not joking at all. very serious. I know it’s not needed, but it helps to point out to people who might modify your code later on that you do indeed want all other exceptions to be raised. it basically prevents someone from adding “when others then null” while you’re on vacation.

Now, before rushing back and starting to sprinkle WHEN OTHERS THEN RAISE all over your code, please read Tom Kyte’s take on this seemingly harmless line of code:

why do people do this?????

EXCEPTION WHEN OTHERS THEN RAISE; END;

what is the point, other than to make the code infinitely harder to debug. You know what you did by coding that?

YOU HIDE THE LINE NUMBERS FROM US. No longer can you tell where the error came from !!!!!

Tom is right. Consider:

SQL> DECLARE
  2     l_var   varchar2 (30);
  3  BEGIN
  4     SELECT   object_name
  5       INTO   l_var
  6       FROM   all_objects
  7      WHERE   ROWNUM <= 2;
  8  END;
  9  /
DECLARE
*
ERROR at line 1:
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 4

Now let’s add WHEN OTHERS THEN RAISE:

SQL> DECLARE
  2     l_var   varchar2 (30);
  3  BEGIN
  4     SELECT   object_name
  5       INTO   l_var
  6       FROM   all_objects
  7      WHERE   ROWNUM <= 2;
  8  EXCEPTION
  9     WHEN OTHERS
 10     THEN
 11        RAISE;
 12  END;
 13  /
DECLARE
*
ERROR at line 1:
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 11

As you can see, WHEN OTHERS THEN RAISE masked the line number where the actual error occurred. In the above example, the real error occurred at line 4 not 11.

WHEN OTHERS THEN NULL is a hidden bug but WHEN OTHERS THEN RAISE hides the bug.

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Enso

Enso is a free application launcher, but it is also more than just that. Enso is similar to Ubiquity, however, Enso works at the Windows operating system level, not just inside your browser. It is available to you in any application you’re using. On the other hand, Ubiquity is open-source, Enso is not. Enso is also similar to Quicksilver on Mac.

Walt Mossberg of the Wall Street Journal explains:

Enso is dead simple to use. You just hold down the Caps Lock key and type an Enso command, which is displayed in a translucent overlay. Once the command is typed, you simply release the Caps Lock key to activate it, and the overlay disappears. If you type fast, it all happens in a flash. For instance, to launch the Firefox Web browser, you just hold down the Caps Lock key and type "open firefox." To look up the meaning of the word "proclivity," you just hold down the Caps Lock key and type "define proclivity."

Other launchers: Launchy and Colibri. Google Desktop can also be used as an application launcher.

CLCL

CLCL is a freeware clipboard caching utility. It allows you to stack things (text, images…) on your clipboard in one batch then bounce once to the destination and paste them all in the appropriate places, one at a time.

Other clipboard enhancers: Jumpcut and iClip for Mac.

AutoHotkey

AutoHotkey is a free, open-source macro tool that allows you to automate almost anything by sending keystrokes and mouse clicks. You can write a mouse or keyboard macro by hand or use the macro recorder. Using AutoHotkey, virtually any key, button, or combination can become a hotkey.

Other macro utilities: TextExpander and Typinator for Mac.

Virtual Desktops

Microsoft PowerToys for Windows XP have many useful (and free) “toys”, but one of the most useful is the “Virtual Desktop Manager”. It allows you to manage up to four virtual desktops, each with a taskbar controller, unique wallpapers, and hotkey support. Virtual desktops provide an excellent way to kill distractions, stay focused and concentrate on the task at hand.

On Linux, both GNOME and KDE have virtual desktops built-in. The Leopard version of Mac OS X added this feature, called Spaces.

Keyboard Shortcuts

Almost all operating systems and applications that run on them have keyboard shortcuts. There is a reason why they are called shortcuts, it’s because once you master them it takes shorter time to perform a task using keyboard shortcuts than using the mouse. The following is a list of common and useful shortcuts:

• Keyboard shortcuts in leading Microsoft products
• Keyboard shortcuts in Mac OS X
• Keyboard shortcuts in Ubuntu
• Keyboard shortcuts in Mozilla Firefox
• Keyboard shortcuts in Gmail
• Keyboard shortcuts in Google Reader

I have been using the above tools for a while. I can now do things on my computer faster than I’ve ever been able to.

Other than the ones mentioned above, what tools or tips do you use that help you be more productive using your computer?

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