Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Jeremy Geelan, Maureen O'Gara, Nancy Y. Nee, Tad Anderson

Related Topics: ColdFusion

ColdFusion: Article

ODBC Escape Sequences

ODBC Escape Sequences

Within the field of computer science, competing products often implement standards differently. Database management systems (DBMSs), with their different syntaxes for SQL queries, are no exception. How can we write queries within our applications that will be compatible with several DBMSs, especially when we need to use functionality that different DBMSs have implemented differently?

Recently, Technomedia Training, Inc., was awarded a contract to deliver our core product, a Web-based human resources management software application, to a new client. The client would be hosting the application, and the IT department's infrastructure and expertise were strictly Oracle-based. However, our application was designed to work with SQL Server 2000. Our challenge was to transform our Web application to make it compatible with an Oracle8i database.

The first step was to convert the database and all its objects from SQL Server 2000 to Oracle8i. (We employed some interesting conversion techniques, but they're a whole subject themselves and we won't cover them in this article.) Next, we discovered that many of the queries within the application didn't work anymore with the Oracle8i database because of differences in implementation of the SQL standard. For example, the following outer join query in Transact-SQL works with SQL Server 2000 but is incompatible with Oracle8i:

SELECT EMP.ID, EMP.NAME, DEP.NAME
FROM EMPLOYEES EMP
LEFT OUTER JOIN DEPARTMENTS DEP ON
DEP.DEPARTMENT_ID = EMP.ID
In Oracle8i, the syntax is:

SELECT EMP.ID,EMP.NAME.DEP.NAME
FROM EMPLOYEES EMP, DEPARTMENTS DEP
WHERE EMP.DEPARTMENT_ID = DEP.ID(+)
We looked at several alternatives for resolving this problem, and concluded that ODBC escape sequences are the best way to make our application's queries compatible with several DBMSs.

Technological Architecture
Our core product is a Web application that uses a standard, three-tier architecture. A ColdFusion Server works with an IIS Web server to run the application code. The ColdFusion Server uses an ODBC driver to connect to the database. Users' Web browsers call up pages from the ColdFusion/IIS servers using the HTTP protocol, and the application works with a SQL Server 2000 database - we need to make it compatible with Oracle8i (see Figure1).

Dealing with DBMS-Specific Queries
To deal with syntax differences among DBMSs, we considered three possible solutions. We could:

1.   Change the application's queries to remove the DBMS-specific elements.
2.   Put conditional statements around all queries with DBMS-specific terms and have both syntaxes present in the code. Then, depending on which DBMS the application is connected to, the appropriate syntax would be used.
3.   Use ODBC escape sequences and let the ODBC driver map to the DBMS-specific syntax.

We'll examine these three possibilities next.

Simple SQL
The first option for dealing with DBMS-specific queries is to remove all terms that are DBMS-specific and to use only SQL syntax that is common to all DBMSs. For example, the SQL Server 2000 syntax for concatenating a first and a last name looks like this:

<cfquery name = "qsEmployees" datasource="Sigal">
SELECT first_name + ' ' + last_name AS name
FROM employees
</cfquery>
Instead, the concatenation could be done outside of the query like this:

<cfquery name = "qsEmployees" datasource="Sigal">
SELECT first_name, last_name, NULL AS name
FROM employees
</cfquery>
<cfloop query = "qsEmployees">
<cfset tmp = QuerySetCell (qsEmployees, "name",
qsEmployees.first_name & " " &

qsEmployees.last_name,
qsEmployees.CurrentRow)
</cfloop>
The advantage of this solution is that the query will work with all types of DBMSs and with all types of drivers, including non-ODBC drivers. However, we discarded this solution because of its disadvantages. If we limit our queries to a lowest-common-denominator SQL, we can no longer use some functionality that is essential to our application. There's no way to execute outer joins, and most date and time functions are excluded. All queries have to be relatively simple, which implies having to restructure certain queries or even sub-dividing them to make them more compatible. In addition, a lot of the processing is transferred from the database to the application code. This incurs a performance penalty, since the database server is optimized for many of the data operations, while the application server is not.

Different Versions of Incompatible Queries
The second option for making DBMS-specific queries compatible with several DBMSs is to create different versions of the query, each version containing DBMS-specific syntax. Using this method, our concatenation example would look like this:

<cfquery name = "qsEmployees" datasource="Sigal">
<cfif application. DBType eq "ORA">
SELECT first_name || ' ' || last_name AS name
FROM employees
<cfelse>
SELECT first_name + ' ' + last_name AS name
FROM employees
</cfif>
</cfquery>
The advantage of this solution is that it's relatively easy to implement. A new, DBMS-specific version of each incompatible query is written and the application executes the appropriate version for the database it's connected to. However, doubling queries makes the application code bigger. Modifying and maintaining the code becomes more complex because changes to a query need to be repeated for each DBMS-specific version. Moreover, this solution doesn't scale with other DBMSs. If one day the need arose to make the application compatible with a DBMS other than Oracle or SQL Server, the whole process would need to be repeated. The code would become even more complex and difficult to modify and to maintain.

ODBC Escape Sequences
Using ODBC escape sequences for the DBMS-specific queries is the third option for making queries compatible with different DBMSs. ODBC escape sequences are a way of coding database functionalities that have different syntaxes in different DBMSs. As we have seen, the syntax for concatenations in Oracle8i is different from that used in SQL Server 2000, but we can use an escape sequence that represents the concatenation functionality provided by the DBMSs instead of the DBMS syntax. The concatenation example now looks like this:

<cfquery name = "qsEmployees" datasource="Sigal">
SELECT {fn concat (first_name, {fn concat (' ', last_name)})}
AS name
FROM employees
</cfquery>

ODBC escape sequences allow queries to be compatible with several DBMSs while giving access to the functionalities that have been implemented differently by different DBMSs. It's important to note that an escape sequence will only work with a DBMS if the DBMS supports the escape sequence functionality. Escape sequences are not implementations of database functionalities. Rather, they are an alternative way of writing a functionality, an alternative syntax that is translated by the ODBC driver into the DBMS syntax. It's possible to have one version of the queries using this technique. This solution also scales much better than the previous one because the queries are not only compatible with Oracle8i and SQL Server 2000, but also with any other DBMS that has an ODBC driver, in the measure that the DBMS supports the functionality represented by the escape sequences. The learning process is simplified because we don't need to learn the DBMS syntax of different DBMSs once we have learned the ODBC escape sequences. However, using ODBC escape sequences can make the code more complex because of the somewhat ornery syntax. You'll need to plan for a learning period for everyone to become comfortable with the new syntax and when to use it. Despite these mild difficulties, ODBC escape sequences are, in our opinion, the best way to deal with the different ways different DBMSs implement certain functionalities.

Using ODBC Escape Sequences
Let's look at how ODBC escape sequences are used. The functionalities that are implemented differently by different DBMSs are coded using a special syntax, called "escape sequences". Escape sequences have the following structure:

  • They are placed within curly braces so the ODBC driver recognizes them.
  • A code that represents the escape sequence type follows the opening curly brace.
  • The escape sequence content is written.

    The ODBC driver reads the escape sequence and translates it into the DBMS-specific syntax before sending the query to the database. ODBC escape sequences can be used for functions, outer joins, LIKE escape characters, GUIDs, intervals, procedure calls, and date, time, and timestamp literals. For example, an escape sequence function looks like this:

    SELECT {fn MonthName (date_membership)}
    AS month_membership
    FROM employees
    An outer join escape sequence has this syntax:

    SELECT emp.id, ent.name
    FROM {oj employees emp
    LEFT OUTER JOIN entities ent
    ON emp.entity_id = ent.id}
    A date literal has this syntax:

    SELECT COUNT(id) AS num
    FROM employees
    WHERE date_membership > {d '2003-01-01'}
    Challenges
    When we started implementing and testing ODBC escape sequences in our application's queries, we discovered that not all ODBC drivers fully implement the ODBC standard. Some of the functions in the ODBC escape sequence specification were not implemented by our Oracle ODBC driver. For example, we weren't able to use the TimeStampDifference() function with the Oracle ODBC driver. In such cases, we used one of the other two alternatives, conditional statements around different versions of the query, or simple SQL with more processing outside the query.

    Another concern was that by using ODBC escape sequences, we were limiting our database connectivity to ODBC drivers. Our company also develops Java objects to extend the functionality of ColdFusion, and we questioned whether the ODBC escape sequences were a good long-term solution, as Java objects use the JDBC protocol. Research revealed that certain JDBC drivers, known as ODBC bridges, use the ODBC protocol. Also, the JDBC protocol specification includes an escape syntax that is very similar to the ODBC escape sequences. Testing with a pure JDBC driver showed that it was compliant with several escape sequences. We strongly recommend testing with the JDBC driver you're planning to use.

    Conclusion
    Although the process of converting an application's queries to be compatible with a new DBMS can be lengthy, using ODBC escape sequences ensures that most of the work will be done only once. It also preserves the application's performance by allowing access to the database functionality, which has different syntaxes in different DBMSs.

    References

  • ODBC escape sequences: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odbc/htm/ odbcescape_sequences_in_odbc.asp
  • JDBC API: http://java.sun.com/products/jdbc/download.html
  • ColdFusion JRun JDBC driversdocumentation: www.macromedia.com/v1/documents/jr31/jdbcref.pdf
  • Comments (0)

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    @ThingsExpo Stories
    With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
    The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...
    Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
    "When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
    Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
    SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
    SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
    SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
    In this presentation, Striim CTO and founder Steve Wilkes will discuss practical strategies for counteracting fraud and cyberattacks by leveraging real-time streaming analytics. In his session at @ThingsExpo, Steve Wilkes, Founder and Chief Technology Officer at Striim, will provide a detailed look into leveraging streaming data management to correlate events in real time, and identify potential breaches across IoT and non-IoT systems throughout the enterprise. Strategies for processing massive ...
    SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
    In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
    SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
    We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
    SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
    SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
    Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
    Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists looked at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deliver...
    In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
    With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...
    IoT solutions exploit operational data generated by Internet-connected smart “things” for the purpose of gaining operational insight and producing “better outcomes” (for example, create new business models, eliminate unscheduled maintenance, etc.). The explosive proliferation of IoT solutions will result in an exponential growth in the volume of IoT data, precipitating significant Information Governance issues: who owns the IoT data, what are the rights/duties of IoT solutions adopters towards t...