Since all of the previous tutorials I’ve posted with regards to data connections have dealt with searching for records and displaying the results, I thought I should post a little tutorial on how to use data connections for inserting, updating and deleting records as well.
You may recall that the tutorial on connecting a form to a database did demonstrate one method of inserting, updating and deleting records from a database. The problem with using bindings to fields in order to modify records in a data connection is that you must set those fields to the values for the current record and then you have to use the data connection object scripting methods like "addNew()", "update()" or "delete()". This can get really awkward if all you’re wanting to do is insert a new record, for instance, and just doesn’t cut it if you want to avoid having to load-in data when the form is opened (the only purpose for the data connection may be such that new records can be inserted or existing ones can be deleted yet displaying existing records is not required).
This small tutorial uses a basic ODBC data connection defined in the form and then modifies it, via script, in order to be able to execute SQL statements which either insert, update or delete records from any table in the database for which the data connection was setup to work with. It then uses a separate data connection to the same database for query purposes only since there’s no sense complicating things with an all-purpose data connection — especially when it comes to running "select" SQL statements in order to iterate through records returned by the query.
The key concept with this tutorial is the fact that the <query> node inside an ODBC data connection (as we saw in the tutorial on selecting specific database records) can be used to execute all sorts of SQL statements — not just "select" queries. This means that if you set the <select> node (inside the <query> node) to be an "insert" SQL statement and open the data connection, the result will be a new record in the database as per the insert statement’s parameters (and the same goes for "update" and "delete" SQL statements). In fact, the XFA 2.4 Specification states, on page 772, that "despite the name [of the <query> node], this element can also be used to delete, insert, and update records."
BOF and EOF Actions
One very important thing to note is that the "Beginning of File" and "End of File" actions on the <query> node’s <recordSet> child node (which describes how records in the data connection are navigated) must be set to "stayBOF" and "stayEOF", respectively, otherwise you may run into serious problems. That is, the result of reaching the beginning or end of the record set when opening the data connection must be to "stay" where you (the record set navigator) are when the SQL statement is one or more of "insert", "update" and "delete".
See the script in the "Database" script object in the sample form for more details on how to specify this. Use the Hierarchy palette to locate it under the root subform.
I’ve designed a form that should put this all into perspective for you as well as give you a very useful script object which you can place in your Custom Library tab and re-use in other forms.
In short, these are the steps I followed to design this form:
- I created the "RunSQLDataConnection" ODBC data connection to my "FormBuilder" database, specifying a short SQL query to the new "movie_comments" table (although any other table would’ve been just fine).
- I created the second "ListComments" ODBC data connection to my "FormBuilder" database, specifying an SQL query that exposes the "username", "title" (movie title obtained from a join on the movie table) and "comment" columns.
- I inserted the various buttons and fields and wrote the scripts.
I’ve included lots of comments through the scripts to detail what’s going on at each stage as well as why certain things are being done so please have look at the sample (note that you don’t have to have the data connections setup in order to open the form and look at the script) and let me know if you have any questions.
Minimum Requirements: Designer 8.0, Acrobat Pro/Std 8.0
Posted by Stefan Cameron on December 18th, 2006
Filed under Data Binding,Scripting,Tutorials
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