Database queries are similar to data sources (XML, CSV, JSON). The important difference is that they are not static, but read dynamically from a database. As a rule, only queries or SELECT statements should be stored at this point. Other statements (INSERT, etc.) may work - but this varies from database type to database type and is not recommended. Instead, such statements should be made with the corresponding workflow action Database query.

Before you can create a new database query, you must create a database connection  if you have not done so already.

CONTENTS

• Creating a database query
• Using the database query
• Testing the query
• Selection form elements
• Examples

Creating a database query

• Open the module "Database queries" and click "New"   in the header of the list (see figure).
• The following data is needed for a Database query:
  • Name: A unique name for the database query
  • Description: An optional description for the database query
  • Connection: The Database connection that should be used
• Enter the SQL statement to be executed for the query in the editor (see figure).

The entered SQL statement is executed as a prepared statement, which prevents SQL injection attacks. You should not and need not use inverted commas (` or '). Also, you can use question marks ( ? ) as placeholders to build queries dynamically. Variables can be used in the SQL statements.

Using the database query

You can access the database query by making a HTTP request to the corresponding database servlet and providing the required parameters as GET parameters. The URL to the database query servlet is as follows.

http://<server>/formcycle/datenabfragedb

The servlet URL is displayed beneath the settings (see figure).
The following URL parameters are supported:

When accessing a database servlet from a form, always use the database URL contained in the global object XFC_METADATA, see also the metadata. For example: XFC_METADATA.urls.datasource_db

Further we recommend you use the script function xutil.getdataquery, so you do not have to setup the servlet request manually. The result of the database query is returned as JSON.

Testing the query

For quick testing of the query the shortcut Ctrl + Enter is provided.

Database queries can be tested directly from the configuration UI. For this purpose a test console is provided below the SQL editor (see figure).
In the header of the console there is a row of buttons for controlling the query:

•  Perform query
  Runs the database query. If query parameters (?) are provided the user will be prompted to input values vor those parameters. Otherwise the result of the query will be displayed directly in the table view.

  
  
  

•  Query parameters
  Mask for inputting values for query parameters. This option is only available if query parameters (?) are used in the SQL query. The individual parameters will be enumerated in the SQL query. Clicking "User parameters for query"   executes the query with the given parameters. The result will be displayed in the table view.
  

  

  
  Actual Query in the SQL editor:

  
  
  

•  Table view
  Query result in table view

  
  
  

•  Source code view
  Query result in JSON format

  
  
  

•  Generated SQL
  Displays the generated SQL statement with input parameter values

  

Selection form elements

If you want to display the returned data as options of a selection element, you can do so easily by opening the formcycleDesigner and selecting the database query as the data source of the selection element.

Queries that are used in selection elements must not have a question mark "?". Queries with a "?" are not offered as a data source for selection elements.

The result of the database query is used to create the options of the selection element in the following order:

All returned columns are added as the value of the HTML attribute col0 (displayed value), col1 (submitted value), col2 (optional value 1), col3 (optional value 2) etc. to the corresponding option element. 

The displayed value is visible to the user directly when selecting an option. The submitted value is the value of the HTML attribute value and it is sent when the form is submitted.

Optional values returned by the database query may be access as follows with JavaScript.

$('[name=sel2]').find('option:selected').attr('col2') // Selects the active option of the selection element named 'sel2' and returns the first optional value. 

Examples

select name, first_name from table where first_name like (?)

This SQL statement returns the names of all persons with a certain first name. The first name to search for is specified via an URL parameter.

URL for running the query:
http://myserver/formcycle/datenquelledb?mandantName=myself&name=demo&queryParameterValues=Robinson

 

select name, first_name from table where id = ?

Retrieves the name of a person with a certain ID. The ID is given as an URL parameter. 

URL for running the query:
http://myserver/formcycle/datenquelledb?mandantName=myself&name=demo&queryParameterValues=100

 

select name, first_name from table where city like(?) AND zip = ?

Retrieves the names of all persons that live in certain city. The city and the ZIP code are given as URL parameters.

URL for running the query:
http://myserver/formcycle/datenquelledb?mandantName=myself&name=demo&queryParameterValues=Paris&queryParameterValues=75001

 

select name, vorname from tabelle where ort like concat(?, '%')

This SQL statement returns the names of all persons who live in a place that starts with the given characters. The '%' character serves as a wildcard for any number of characters. Depending on the DBMS used, the syntax may differ slightly (here: MySQL). The requested value is passed via URL parameters.

URL for running the query:
http://myserver/formcycle/datenquelledb?mandantName=myself&name=demo&queryParameterValues=Par

 

select name, vorname from tabelle where lower(ort) like concat('%', lower(?), '%')

This SQL statement returns the names of all persons who live in a place that contains the given characters. Upper/lower case spelling is irrelevant becauce the statement converts both, the value column and the actual filter value to lower case (lower(...)). The requested value is passed via URL parameters.

URL for running the query:
http://myserver/formcycle/datenquelledb?mandantName=myself&name=demo&queryParameterValues=aRi