We covered this topic from a different angle a month ago in convertign excel to apex and printing from apex. Both of these blog entries talk about how to use Schema as a Service to solve a problem. Some good references on Schema as a Service can be found at
When we login to access the database we are asked to present the schema that we created, a username, and a password. Note in this example we are either using the external free service apex.oracle.com or the Oracle corporate service for employees apex.oraclecorp.com. The two services are exactly the same. As an Oracle employee I do not have access to the public free service and am encouraged to use the internal service for employees. The user interface is the same but screen shots will bounce between the two as we document how to do things.
Once we login we see a main menu system that allows us to manage application, manage tables in the database, to team development, and download and install customer applications.
The Object Browser allows us to look at the data in the database. The SQL Commands allow us to make queries into the database. The SQL Scripts allows us to load and save sql commands to run against the database. Utilities allows us to load and unload data. The REST ful service allows us to define html interfaces into the database. If we look at the Object Browser, we can look at table definitions and data stored in tables.
We can use the SQL Commands tab to execute select statements against a table. For example, if we want to look at part number B77077 we can select it from the pricelist by matching the column part_number. We should get back one entry since there is only one part for this part number.
If we search for part number B77473 we get back multiple entries that are the same part number. This search returns six lines of data with more data in other columns than the previous select statement.
The SQL Scripts allows you to load scripts to execute from your laptop or desktop. You can take queries that have run against other servers and run them against this server.
Up to this point we have looked at how to write queries, run queries, and execute queries. We need to look at how to load data so that we have something to query against. This is done in the Utilities section of the Schema as a Service. Typically we start with a data source either as an XML source or an Excel spreadsheet. We will look first at taking an Excel spreadsheet like the one below and importing it into a table.
Note that the spreadsheet is well defined and headers exist for the data. We do have some comments at the top that we need to delete so that the first row becomes the column names in our new table. Step one is to save the sheet as a comma separated value file. Step two is to edit this file and delete the comment and blank like. Step three is to upload the file into the Schema as a Service web site.
At this point we have a data source loaded and ready to drop into a table. The user interface allows us to define the column type and tries to figure out if everything is character strings, numbers, or dates. The tools is good at the import but typically fails at character length and throws exceptions on specific rows. If this happens you can either manually enter the data or re-import the data into an existing table. Doing this can potentially cause replication of data so deleting the new table and re-importing into a new table might be a good thing. You have to play at this point to import your data and get the right column definitions to import all of your data.
Alternatively we can import xml data into an existing table. This is the same process of how we backup our data by exporting it as xml.
At this point we have loaded data using a spreadsheet or csv file and an xml file. We can query the database by entering sql commands or loading sql scripts. We could load data from a sql script if we wanted but larger amounts of data needs to be imported with a file. Unfortunately, we can not take a table from an on-premise database or an rman backup and restore into this database. We can't unplug a pdb and plug it into this instance. This service does have limitations but for free or less than $200 per month, the service provides a lot of functionality.
To create an application to read and display our data, we must create an application. To do this we go into the application development interface of Schema as a Service.
We select the Application Builder tab at the top and click on Create icon. This takes us to a selection of what type of application to build. We are going to build a desktop application since it has the most function options. We could have easily selected the mobile option which formats displays for a smaller screen format.
We have to select a name for our application. In this example we are calling it Sample_DB since we are just going to query our database and display contents of a table.
We are going to select one page. Note that we can create multiple pages to display different information or views into a table. In our previous blog entry on translating excel to apex we created a page to display the cost of archive and the cost of storage on different pages. In this example we are going to create one page and one page only.
If we have shared components from other apps or want to create libraries that can called from other apps, we have the option at this point to define that. We are not going to do this but just create a basic application to query a database.
We can create a variety of authorization sources to protect our data. In this example we are going to allow anyone to read and write our table. We select no authorization. We could use an external source or look at the user table in the database to authenticate users. For this example, we will leave everything open for our application.
We get a final confirmation screen (not shown) and create the application. When the create is finished we see the following screen that lets us either run the application or edit it.
If we click on the Home icon we can edit the page. This screen is a little daunting. There are to many choices and things that you can do. There are different areas, breadcrumbs for page to page navigation, and items that you can drop into a screen. In this example we are going to add a region by hovering the mouse over the Content Body and right clicking the mouse. This allows us to create a new region in the body of our page.
Note that a new region is created and is highlighted in the editor. We are going to edit the content type. We have a wide variety of options. We could type in static text and this basically becomes a static web page. Note that we could create a graph or chart. We could create a classic report. We could create a form to submit data and query a table. We will use the interactive report because it allows us to enter sql for a query into our table.
In this example we will enter the select statement in the query box. We could pop this box into another window for full screen editing. For our example we are doing a simple select * into our table with select * from pricelist.
When we click the run button at the top right we execute this code and display it in a new window. We can sort this data, we can change the query and click Go. This is an interactive from to read data from our table. If we wanted to restrict the user from reading all of the data we would have selected a standard report rather than an interactive report.
The final part of our tutorial is creation of a REST api for our data. We would like to be able to go to a web page and display the data in the table. For example, if we want to look at the description of part number B77077 it would be nice to do it from a web page or get command at the command line. To do this we go to the SQL Workshop tab and click the RESTful Service icon at the top right.
Again, this screen is a little daunting. We get a blank screen with a create button. Clicking the create button takes to a screen where we need to enter information that might not be very familiar.
The screen we see is asking us to enter a name for our service, a template, and a resource handler. Looking at this for the first time, I am clueless as to what this means. Fortunately, there is an example on how to enter this information if you scroll down and click on the Example button.
If we look at the example we see that the service name is the header that we will hit from our web page.
In our example we are going to create a cloud RESTapi where we expose the pricelist. In this example we call the service cloud. We call the resource template pricelist and allow the user to pass in a part_number to query. In the resource handler we go a get function that does a select from the table. We could pass in the part number that we want to read but for simplicity we ignore the part number and return all rows in the table. Once we click save, we have exposed our table to a web query with no authentication.
Once we have created our REST service we can query the database from a we browser using the url of the apex server/pls/apex/(schema name)/pricelist/(part number). In this example we go to apex.oraclecorp.com/pls/apex/parterncloud/pricelist/B77077. It executes the select statement and returns all rows in the table using JSON format.
In summary, we are able to upload, query, and display datatbase data using http and https protocols. We can upload data in xml or csv format. We can query the database using web based tools or REST interfaces. We can display data either by developing a web based program to display data or pull the data from a REST interface and get the data in JSON format. This service is free if your database size is small. If we have a larger database we can pay for the service as well as host the application to read the data. We have the option to read the data from a REST interface and pull it into an application server at a different location. We did not look at uploading data with a PUT interface through the REST service but we could have done this as well. Up next, how do we implement this same service in AWS or Azure.