Oracle Apex Interview Questions and Answers
Last updated on 27th Sep 2020, Blog, Interview Question
Oracle Application Express (Which is called Oracle Apex in Short form) is a web-based development environment that runs on Oracle database. Hence, its widely used in enterprises where the Oracle database is in use
1. What is Oracle Apex?
The very important and core feature of Oracle Apex is that it is tightly integrated with Oracle Database and it has the full capability of web development environment. We have the option for the customization of the theme or we can make use of the basic theme for the look & feel of the application.
2. What are the advantages of APEX?
The following are the advantages of APEX:
- There is no requirement of license as it is free.
- It is used for the building application as it is a fast learning curve for developers and the users .
- We also have the option of building web applications which are fast and secure with the help of APEX.
- In this we have a lot of scope for customization of the application as per the requirement of user and the programmer.
- In this the deployment of applications is a very simple and easy task as “Import & Export”.
- Oracle tables are used to store Apex Framework and meta-data which runs on live Oracle DB’s.
3. Who uses APEX?
If the person uses the oracle database and he/she wants to build a rich web application with the reports, forms, charts, drill downs and dashboards with limited Java experienced developers in a short time frame then the Oracle APEX is the most likely good consideration.
4. How APEX Architecture works?
Then the URL request from the browser is translated into an appropriate APEX PL/SQL call by either Oracle HTTP Server (Apache) with mod_plsql plugin or Embedded PL/SQL Gateway. This is varied by the type of APEX installation on the oracle database. After the processing of data the results are relayed back to the browser as HTML. This cycle takes place every time a user requests or submit a page. Then the application session state is maintained in the database tables.
APEX can be installed in two ways .DBAs are more concerned about it than the developers but this determines how the URL is being translated.
5. What is the cost of APEX and where one can get it?
APEX comes pre-installed and it is completely integrated with Oracle Database Express Edition(XE). For all other editions of the Oracle Database, Oracle Application Express comes as a free add-on which can be downloaded and installed. If you choose to “try before you buy”, or since it’s free, “try before you install”, you can also use the hosted APEX Online facility.
This facility allows the user for creating and running complete applications just as he/she would on his/her own equipment.
6. What are the skills required for APEX developers?
7. Mention the types of APEX Users?
They are divided into 3 they are:
- Instance Administrators.
- Workspace Administrators.
8. Define the support for APEX that exists?
Application Express can be defined as the best community for someone to help deliver, develop & make use of the APEX applications. The basic support is from the APEX forum of Oracle Tech Network. We are also able to find out the answers & tips related to development from in & out of Oracle.
9. What kind of activities can we do for apex as apex dba?
- setup of apex environment
- SSL configuration
- USER access
- Security modal definition
- ad hoc issue and resolution
- Patching /Performance
10. What are the platforms that support Oracle Apex?
The below mentioned supports the Oracle Apex:
- HP Tru64 UNIX (Compaq / DEC)
- HP-UX PA –RISC
- HP-UX Itanium
- Linux x86-64
- Linux Itanium
- Microsoft Windows – x64
- Microsoft Windows – 64 -bit Itanium
- Solaris Operating System – SPARC – 64 bit
- Solaris x86
- Microsoft Windows – 32 –bit
- Mac OS X Server
- Linux x86
- Linux on Power
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11. What are the considerations which are required for the Static Keyword in Apex?
Following are some of the considerations which are required for the Static keyword in Apex.
- We cannot make an Apex class static.
- The Static keyword in Apex is only allowed in the outer class.
- The Static variables in Apex are not exchanged like a View State part.
- Static block and static variables keep running inside and out in the Apex in which they are made in a class.
- Static variables are static just to the demand’s extent in the Apex.
12. Can you state some of the uses of APEX?
- It helps in fabricating the proficient looking web applications which are both efficient and secure.
- It keeps running on and lives in the Oracle database. The Apex framework and metadata are put away in Oracle tables.
- It is FREE and there is no requirement of authorization in this.
- It also has a quick expectation for learning and adapting to build the application.
- The application deployment is as simple as ‘Export and Import’ if hard coded references of values that change between situations are avoided from this.
- It is having the parcel of extension for customization of use, look and feel.
- It is adaptable for high client volume. ASKTOM, previous ORACLE METALINK and MANY APPLICATIONS are mainly built utilizing APEX.
- It can usually be configured for utilizing Oracle SSO and EBS fnd client repository.
13. How can one know what version of apex is installed in the system?
If we are having access to dba view then we should select comp_name, version, status from dba_registry or schema user.
14. How can the developer know in which version they are working?
For checking the version the person needs to check schema name OR should select version_no from apex_release; to check the same.
15. If someone forgets admin password, how will he login to apex application?
We need to call sql scripts to reset the password @apxchpwd.sql (this is the same as alter user username identified by password).
16. By which user we connect to an apex application?
17. Does APEX work with non-Oracle databases?
18. How will you validate apex?
We can validate the apex by Utlrp.sql or SQL, exec validate_apex; (If the version of APEX is 2.0 or above) OR SQL & exec validate_htmldb; (If the version of APEX version is prior to 2.0)
19. What is APEX syntax?
APEX syntax is defined as the syntax which has different features such as variable declaration for storing the different values in the memory. The queries will be like SOQL that can be used for execution of the queries, loop statements for performing the iterations in performing the operations, flow control statements can be used to control the flow execution whether to start or stop the execution process, DML statements can be used for the manipulation of the data by executing the queries.
20. What does the APEX development environment contain?
The Salesforce APEX development environment is having various features and processes to be followed for the successful development of an application and also to set up an edition as per the required entity. The code can be developed either in a local developer edition or a sandbox of Salesforce. As per the standards, the code will usually be developed in the Sandbox and will be deployed into production.
The different operations which will be performed during the development of the code its compilation process, debugging the code, testing the code and also its application, performing the SOQL query execution and its efficiency, color coding, auto-alignment and auto-completion of the build process. The main step of execution of the code in Salesforce will include the login action into the Salesforce sandbox or consoling before performing all these operations.
21. What are the different data types in APEX?
The different data types that are available in the APEX language are Primitive Data Type (Integer, Long, Double, Date, DateTime, ID, or Boolean and String), Collections (Lists, Maps, and Sets) and Enum Classes, Interfaces and Objects. The Primitive data type Integer can be any value of a 32-bit number and it will be having some range similar to that of Java programming language. A Boolean data type will be having a true and false value. The Date data type can only store the date value but not the time.
The Primitive data type Long can be any value of a 64-bit number and it will have some range similar to that of Java programming language. The String data type is a set of characters that will be initialized within single quotes. Enum is an abstract kind of data type.
22. What are the different Collections in APEX?
The different collection data structures in the APEX are Lists, Maps, and Sets. A List will be having any type of data stored in it such as primitives, collections, different types of complex objects or schema objects. There will also be different types of methods available in the lists for performing different operations such as to retrieve the size of the list, to clear the contents, to get the details of the list and to update, delete and add the records or values into it. The same functionalities also exist for Set and Maps but with different functionalities.
23. What is SOQL in APEX?
SOQL is defined as the Salesforce Object Query Language which was designed and developed to work with Salesforce Database.
24. Explain the Security features in APEX?
There are various security rules and features in APEX that are enforced while sharing the data or while running the code for the protection of the application features and code. There are various sharing security features which are also to be enforced and different levels of security.
25. How does APEX integrate with the database?
Oracle Application Express is defined as purely a database application. The IDE, the menus, and all of the screens we see in APEX are written in PL/SQL. The meta data for all of those screens, reports and menus are getting stored in the relational tables within the database. When we point our browser at the APEX URL, the Oracle HTTP listener (Apache +mod_plsql or the PL/SQL gateway, depending on database version) receives that call and it uses PL/SQL and the metadata stored in database tables for painting the welcome screen.
When we log into APEX then we are using an actual database user ID. This user ID is having association with a role within the database and these roles determine what access the programmer will have. If we are an administrator then we are having access to create users and workspaces.
As a developer we have access for creating new applications. If we are configured as an end-user then we will be able to run one or more applications. Oracle Application Express is integrated with the Oracle Database as no environment is. If we want to extend the basic functionality of APEX, there is no requirement for learning additional languages or linking in additional libraries. On the rare occasions we need to extend functionality then we will either use SQL for data access or PL/SQL when there is a requirement of the procedural code.
26. What applications come with APEX?
The current version of the APEX makes allowance to the programmer for downloading pre- packaged applications to us for learning from and/or modify for our own uses. We can currently download it (form Oracle’s Technology site):
Employee Directory Lookup – This is exactly the same as what it sounds like.
Ask The Expert – It is the Question and Answer Site ala “ask tom”.
Bug Tracker – It is used for logging and tracking bug reports.
Discussion Forum – It is used for threaded chat, user management and more.
Document Library – It is the multi-user document repository (Word, Excel, etc).
Project Issue Tracker – It is used for defining, assigning and reporting project issues.
Online Store – It is used as a catalog and shopping cart.
Software Projects – It works as the Project task tracker.
27. Where can one try APEX?
As we can sign up for a free account at APEX.ORACLE.COM (Oracle’s hosted Application Express site). When we sign up for an account then we should identify the work area name that we want to use and also identify an administrator. From there we can create applications and also users just as we can do on our own hardware and systems.apex.oracle.com which is not intended for production systems, it is intended for exploration and testing. For additional hosting companies, check out the Oracle.
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28. Explain the kind of support that exists for APEX?
Application Express has a robust community for helping the programmer in developing, delivering and using the APEX applications. The first point of support would be APEX Forum that is resided on Oracle Technology Network. This forum provides useful tips and answers from many experts both internal and external of Oracle..
Other sites include:
- THE APEX WIKI – It is termed as the wikipedia for the APEX crowd.
- APEX STUDIO – It is the community created which has applications available for downloading.
- APEX MAILING LIST – Here we can sign up for information and Question & Answers.
- THE ORACLE APEX COMMUNITY LISTING – This is the list which is growing daily.
29. Explain something about virtual class in the Apex programming?
In a domain where the user is leading the protest situated sort of programming then a virtual class is a term alluded to a settled kind of internal class whose limit alongside the part factors can be effortlessly abrogated and furthermore renamed by the alternate sub classes of some other outer class. Virtual classes are defined as something that intently looks similar to the virtual limits of the program.
30. How are APEX Application components stored inside DB?
This is the first of a 3 part series on embedding files in our APEX application. APEX allows us to embed static web files (CSS, JS, images, etc) into our application. This functionality had removed the need to store the web files on a web server that is required for some applications.
To upload our file into the application we must go to Shared Components & Static Files. Click on the Create button. On the Create page, we can upload a file and either associates the file to a specific application or no application. Files that are in association with a specific application should be having a unique filename within its parent application. It can then be referenced (most likely in a page template) using the #APP_IMAGES# substitution string. Files which are not associated with a specific application are available to all the applications within the workspace and can be referenced (most likely in a page template) using the #WORKSPACE_IMAGES# substitution string. Files which are added to the application aren’t stored on the web server.
They are stored in the database. For high traffic applications, this may not be a great idea and we may want to look at storing them on the web.
31. Say about the statement “APEX a RAD Tool”?
As we can see that the APEX is so firmly incorporated into the database, we would prototype screens while sitting with the client. The Object Browser helps in enabling us to make database questions, for example, tables notwithstanding seeing those same articles. This allows us to make protests on the fly and after that construct tables around those articles.
The IDE, includes the above Table developer and all applications that are kept running inside a browser. Turnaround time is quick. As the APEX is revelatory then we can without much of a stretch roll out improvements progressively by means of the implicit wizards.
Since APEX controls the session data for all of us and because we utilize the security structure incorporated with the Oracle Database, we would concentrate on delivering the applications, not on association setup and other typical advancement time wasters.
32. What are a couple of limitations (points to recall) of Savepoint or Transaction Control in Apex?
- The limitation is each savepoint that we set against the governor limit for DML proclamations.
- Static variables are not returned amid a rollback. If we attempt to run the trigger once more, the static variables hold the qualities from the main run.
- Each rollback helps in the representation of a mark against the governor limit for DML articulations. We will get a Runtime mistake if we are attempting to rollback the extraordinary database circumstances.
- The ID on a sObject embedded subsequent for setting a savepoint isn’t getting cleared after a rollback.
33. What is the present version of APEX and for what reason would it be a good idea for me to update?
The Beta version APEX 4.2 is available in the market a few weeks back. This new form of the APEX 4.2 offers various upgrades. The most helpful are as follows:
Print to PDF – The users are able to send out their reports and screens to PDF yield.
Migrate from MS-Access – By making use of the export tool and the Access Migration Workbench, the user can relocate client applications to APEX.
Calendar Widget – The older forms of the APEX had a date-book gadget yet now clients are able to pick between day, week or month date-books.
Improved Page and Region Caches – As the caching enhances the execution.
Application Builder Defaults – The engineer can set defaults for wizards for diminishing improvement time (fundamental themes for development). The advantages for updating the incorporate execution upgrades and extra usability features for both the designer and the end client.
34. By what method would we be able to hard delete a record utilizing an Apex class/by code?
ALL ROWS keywords can be utilized for getting every one of the records incorporated in the recycle bin.
35. How might we refer to a present page id in Apex?
If we want to recover or refer to a required ID in the Visualforce page at that point, we can simply refer to it by making use of a standard controller.
36. What is an apex scheduler?
It is the essential feature which is utilized just to invoke the Apex classes to enable them to keep running at unequivocal circumstances, to start with, execute the Schedulable assemblage for the class, at that point express the calendar by using either the Schedule Apex page or the System.
37. What is the current version of APEX and why should I upgrade?
Beta version APEX 4.2 is released a couple of weeks back. This new version offers many enhancements.
- Users can choose to export their reports and screens to PDF output.
- Migrate from MS-Access
- Using an export tool and the Access Migration Workbench, you can migrate user applications to APE
- Calendar Widget
- Older versions included a calendar widget but now users can choose between day, week, or month calendars.
- Improved Page and Region Caches Caching improves performance.
- Application Builder Defaults
- The developer can set defaults for wizards to reduce development time (basically themes for development).The benefits of upgrading include performance enhancements and additional usability features for both the developer and the end user.
- The abstract classes in Salesforce Apex are the classes that involve at least one dynamic strategy. A conjectural method is an approach that is checked however it contains no use at all.
38. Clarify a couple of considerations required for the Static Keyword in Apex.
Here are a couple of considerations required for the Static keyword in Apex.
- You cannot make an Apex class static.
- Static is just allowed in the outer class.
- The Static variables are not mainly exchanged like a View State part.
- Static block and static variables keep running inside and out in which they are made in a class.
- Static variables are static just to the demand’s extent.
39. What are a couple of Considerations about Trigger?
- Upsert triggers fire both before and after the insert or when update triggers as proper.
- Merge triggers fires both
- Field history isn’t recorded until the trigger ends. If you question field history in a trigger, you won’t perceive any history for the present transaction.
- You can just utilize the webService keyword in the trigger when it is in a technique characterized as offbeat; that is, the point at which the strategy is described with the @future keyword.
- A trigger conjured by an insert, update or delete of the recurring event or repeating task brings about a runtime error when the trigger is brought in bulk from the Force.com API.
- Merge trigger doesn’t fire their own trigger rather they fire update or delete of losing and winning records individually.
40. Differentiate between Ajax and ActionPoller?
ActionPoller is a clock in Apex that empowers an AJAX refresh request to be sent to the server as is told by a period between the time that the software developer decides.
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41. Difference Between Trigger.new And Trigger.old In Apex?
- This command is used to return the list of new forms of object records
- It is important to keep in mind that the Objects list is only accessible in the update and delete triggers
- i.e., Trigger.new is accessible before and after inserts, before and after the update.
- In Trigger.new the records must be changed in before triggers.
- This command is used to return the list of old variants of the sObject records.
- It is important to keep in mind that the sObject list is only available in delete and update triggers.
- Trigger.old is accessible after inserting, after the update, before deleting and after updating.
42.What is the distinction amongst public and Global class in Apex?
The Public access modifier is not quite the same as people in general modifiers in Java. The public class can be accessed inside an application or namespace. While the Global class is mainly noticeable wherever: in any of the applications or the namespace. The Webservice must be proclaimed as Global so it can be accessed outside of the application. The global variable is like an open modifier in Java.
43. What is outputLink?
It is mainly a connection with URL. This part is rendered in HTML as an anchor tag with a href property. The body of the OutputLink is a content or picture that shows the connection.
44. What is the utilization of interfaces?
An interface takes after a class in which none of the strategies have been executed—the system marks are there, yet the body of each methodology is void. To use an interface, another class must realize it by giving a body to most of the procedures contained in the interface.
Interfaces can give a layer of reflection to your code. They isolate specific execution of a system from the declaration for that procedure. In this manner, you can have unmistakable use of a methodology in perspective of your particular application.
45. What is Apex Interface?
An interface is a group of unimplemented strategies. This will indicate the signature of the strategy, kinds of inputs that we pass the technique determine what compose is given as a yield.
NOTE: Generally the interface techniques we give it as a global.
47.What is the distinction between apex:pageMessages, apex:pageMessage, apex: Message and apex: Messages?
apex:PageMessages: This part shows all messages that were produced for all the components on the present page, introduced utilizing the salesforce styling. This will display both salesforce produced messages and also custom messages added to the ApexPages class.
apex:PageMessage: Apex: PageMessage is a segment that includes a single message on the page. This is utilized to show custom messages utilizing the salesforce formatting.
apex:Message: apex: Message is utilized to show a mistake on just a particular field. It is utilized to enable developers to handle particular mistakes in the particular area.
apex:Messages: apex: Messages is like apex: Message yet it shows all the errors..
48. What are the different type of apex users
Users are divided into three primary roles developer, Workspace administrators and Instance administrators
49. Some views of apex
50. Which user in apex owns the sso module.
51. Which scripts need for the registration process for SSO?
52. How will you enable SSO for apex application?
- Login to APEX_030200
53. How will you direct your application to use https instead of http?
Create wallet from apache home (wallet should be in ready state)
- configure ssl.conf file
- restart apache
- verify with opmnctl status -l
54. I have installed Oracle 11g Enterprise Database with a view to use the embedded APEX but don’t know how to launch it.
Oracle apex by default while installation of oracle DB .But you need to configure access mechanism to launch APEX application.
1) Apache (Web Server)
2) Embedded PL/SQL gateway
3) Oracle Listener
55. What is the difference between varchar and varchar2 data types?
Varchar can store up to 2000 bytes and varchar2 can store up to 4000 bytes. While Varchar will occupy space for a NULL value, Varchar2 will not occupy any space. They are differentiated by space.
56. What is Oracle Application Express?
57. Are there any limitations in using Oracle XE?
XE is free but Oracle has built certain limitations into the product. The first limitation is a memory. Oracle Database XE can address only 1GB of RAM. This limitation mainly affects how many users can access the database concurrently and how well it performs. The second limit is that XE will only use one CPU. XE will run on a multi -CPU computer but won’t scale up to use those CPUs. This functionality requires Oracle Database Standard Edition or Enterprise Edition. The third limit is that only a single XE database can run on any given computer. You do not need a database for each application. Instead, Oracle uses the concept of schemas to separate applications. Finally, a 4GB limit is enforced on disk space. 4GB is a huge amount of storage for most applications. You can also use APEX to link to other databases (on other servers) for more storage as needed.
58. Should static files be placed in the database?
59. What is WITH CHECK OPTION?
The WITH CHECK option clause specifies the level of check to be done in DML statements. It aids in preventing changes to a view that would produce results not contained in the subquery.
60. What is a hash cluster?
Hash Cluster is a technique used for storing the table to make it faster to retrieve. It orders to retrieve the rows from the table, apply the hash value on the table.
61. What is BLOB datatype?
A BLOB data type is a binary string with a varying length which is used in storing two gigabytes memory. Length should be stated in Bytes for the BLOB.
62. What are the SET operators?
The following are the advantages of APEX:
- No license required, it is free.
- To build an application it is a fast learning curve for developers.
- We can build web applications that are fast & secure through APEX.
- There is a lot of scope for customization of the application as per our requirement.Deployment of application is very simple as “Import & Export”.
If any hard code with reference to values varies between environments are avoided.Apex Framework & meta-data is stored in Oracle tables. It runs on live Oracle DB’s.
63. What is RAW datatype?
RAW data type is used in storing values in binary data format. The maximum size of a RAW in a table is 32767 bytes.
64. What is NULL value in Oracle?
The NULL value represents unknown or missing data. It is used as a place holder or represented as a default entry indicating that no actual data is present.
65. What is the use of NVL function?
The NVL function is used for replacing NULL values with given or another value. E.g. NVL(Value, replace value)
66. What is the fastest query method to fetch data from the table?
You can use ROWID to fetch Row from the table. The use of ROW ID is the fastest query method for fetching data from the table.
67. SQL Statement that defines a foreign key constraint on column DEPT NO1 of EMP1 Table?
- CREATE TABLE EMP1 (empno NUMBER(301), name VARCHAR(45), deptno NUMBER(5,3), NOT NULL, CONSTRAINT emp1_deptno1_fk FOREIGN KEY deptno1 REFERENCES dept1(deptno1));
68. Where can I get more information?
In addition to the OTN forums and community sites, Application Express has a huge following in the blogosphere. Many expert level resources maintain blogs about APEX. Some particularly well known blogs are:
SCOTT SPENDOLINI– APEX Guru and owner of Sumner Technologies (an APEX Training, Services, and Consulting company).
PATRICK WOLF– Inside Oracle APEX, Patrick is a long-time Oracle veteran.
DIMITRI GELLIS – Another long-time Oracle vetand co-founder of APEX Evangelists, an APEX specific company, with John Scott.
JOHN SCOTT– As mentioned above, co-founder of APEX Evangelists, an Oracle ACE, and Application Express Developer of the Year for2006.
You can find all of these and more at the OTN COMMUNITY SITE.
69. What are DML Commands?
Delete, Update, Merge & Commit are the termed as the DML Commands.
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