Development

1. Style: there're two styles that come with APEX 5.0: Blue and Gray. You can start from one of those and see how your application changes color. It will set predefined colors for the different parts of the templates.
   
   
2. Color Wheel: when you want to quickly change your colors, an easy way to see different options is by using the Color Wheel. You've two modes: monochroom (2 points) and dual color (3 points - see screenshot). By changing one point it will map the other point to a complementary color. Next you can move the third point to play more with those colors.
   
   
3. Global Colors: if the Color Wheel is not specific enough for what you need, you can start by customising the Global Colors. Those are the main colors of the Universal Theme and used to drive the specific components. You can still customise the different components e.g. the header by clicking further down in the list (see next screenshot).
   
   
4. Containers etc. will allow you to define the specific components. A check icon will say it's the standard color coming with the selected style. An "x" means the color was changed and an "!" means the contrast is probably not great.

• Revert to a previous state of your code base automatically.

• Create branches of your PL/SQL code base, switch between them and merge them whenever you want automatically.

• Clone your code base and have your team edit the same logical PL/SQL code units at the same time without overwriting each others updates.

• Pull changes from other developers and merge them easily.

As you know, NaN is a “Not a Number”.
How do you think, what would be the result of the following query? (0f/0 == NaN)

select count(*) cnt from dual where rownum < 0f/0;

SQL> select count(*) cnt, 0f/0 from dual where rownum < 0f/0;

       CNT       0F/0
---------- ----------
         1        Nan

1 row selected.

select count(*) cnt from dual where 1f/0 < 0f/0;

SQL> select count(*) cnt from dual where 1f/0 < 0f/0;

       CNT
----------
         1

1 row selected.

Spoiler:: PS SelectShow

1 * X < 0 * Y

I never thought I would have to optimize so simple query as

select col1, col2, col4, col7 from table where rownum=1

(even though I read recently “SELECT * FROM TABLE” Runs Out Of TEMP Space)
But a few days ago frequent executions of this query caused big problems on the one of our databases(11.2.0.3) because of adaptive serial direct path reads.

I don’t know why, but I felt intuitively that full table scan with “First K rows” optimization (“_optimizer_rownum_pred_based_fkr“=true) should turn off adaptive serial direct path reads. It seems quite logical to me.

PS. Unfortunately I had a little time, so I didn’t investigate what process and why it was doing that, I just created profile with “index full scan” access, and it completely solved the problem.

At the last JavaOne conference I presented a session titled "Developing On-Device Java Mobile Apps for iOS...and Android Too"

The recording of this session just became available, and I wanted to share it with you.

This session should be a good introduction to how Oracle enables Java developers to take their skills to the mobile world.

The first 28 minutes provide the overview, but if you are not into slides fast forward to minute 29 and start watching the extensive demo of developing an iOS application with Java and Eclipse. 

<br />

I’ve just noticed an interesting thing:

Assume, that we have a simple query with “MIN(ID)” that works through “Index full scan(MIN/MAX)”:

SQL> explain plan for
  2  select
  3     min(ID)      as x
  4  from tab1
  5  where ID is not null;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------
Plan hash value: 4170136576

---------------------------------------------------------------------------------------
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |         |     1 |     4 |     3   (0)| 00:00:01 |
|   1 |  SORT AGGREGATE             |         |     1 |     4 |            |          |
|   2 |   FIRST ROW                 |         |     1 |     4 |     3   (0)| 00:00:01 |
|*  3 |    INDEX FULL SCAN (MIN/MAX)| IX_TAB1 |     1 |     4 |     3   (0)| 00:00:01 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter("ID" IS NOT NULL)

create table tab1(id, x, padding)
as 
   with gen as (select level n from dual connect by level<=1000)
   select g1.n, g2.n, rpad(rownum,10,'x')
   from gen g1,gen g2;
create index ix_tab1 on tab1(id, x);
exec dbms_stats.gather_table_stats('','TAB1');

SQL> explain plan for
  2  select
  3     min(ID)      as x
  4   , min(ID)+1000 as x1000
  5  from tab1
  6  where ID is not null;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------
Plan hash value: 3397888171

---------------------------------------------------------------------------------
| Id  | Operation             | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------
|   0 | SELECT STATEMENT      |         |     1 |     4 |  3075  (17)| 00:00:02 |
|   1 |  SORT AGGREGATE       |         |     1 |     4 |            |          |
|*  2 |   INDEX FAST FULL SCAN| IX_TAB1 |   999K|  3906K|  3075  (17)| 00:00:02 |
---------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - filter("ID" IS NOT NULL)

At first I thought it was the old limitation from “MIN/MAX index access is not used if query has multiple MIN/MAX functions (Doc ID 316467.1)”, but we can get same plan by using hint:

SQL> explain plan for
  2  select/*+ index(tab1) */
  3     min(ID)      as x
  4   , min(ID)+1000 as x1000
  5  from tab1
  6  where ID is not null;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------
Plan hash value: 4170136576

---------------------------------------------------------------------------------------
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |         |     1 |     4 |  3433  (22)| 00:00:02 |
|   1 |  SORT AGGREGATE             |         |     1 |     4 |            |          |
|   2 |   FIRST ROW                 |         |   999K|  3906K|  3433  (22)| 00:00:02 |
|*  3 |    INDEX FULL SCAN (MIN/MAX)| IX_TAB1 |   999K|  3906K|  3433  (22)| 00:00:02 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter("ID" IS NOT NULL)

So, we can see that the real problem lies in the wrong cardinality calculation.

Of course, we can avoid this problem using the old method – with simple inner view:

SQL> explain plan for
  2  select x, x+1000
  3  from (
  4        select
  5           min(ID)      as x
  6        from tab1
  7        where ID is not null
  8       );

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------
Plan hash value: 2347179087

----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |     1 |    13 |     3   (0)| 00:00:01 |
|   1 |  VIEW                        |         |     1 |    13 |     3   (0)| 00:00:01 |
|   2 |   SORT AGGREGATE             |         |     1 |     4 |            |          |
|   3 |    FIRST ROW                 |         |     1 |     4 |     3   (0)| 00:00:01 |
|*  4 |     INDEX FULL SCAN (MIN/MAX)| IX_TAB1 |     1 |     4 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   4 - filter("ID" IS NOT NULL)

Want to use Eclipse to build an on-device mobile application that runs on iOS devices (iPhones and iPads)?

No problem - here is a step by step demo on how to do this:

Oh, and by the way the same app will function also on Android without any changes to the code :-)  

This is an extract from an online seminar that I recorded for one of Oracle's Virtual Technology Summits - and I figured people who didn't sign up for that event might still benefit from having access to the demo part of the video.

In the demo I show how to build an on-device app that access local data as well as remote data through web services, and how easy it is to integrate device features too.

If you want to try this on your own, get a copy of the Oracle Enterprise Pack for Eclipse, and follow the setup steps in the tutorial here.

And then just follow the video steps.

The location of the web service I accessed is at: http://wsf.cdyne.com/WeatherWS/Weather.asmx?WSDL

And the Java classes I use to simulate local data are  here.