If you haven't been using the
cfqueryparam tag, chances are you had a baptism by fire this week. As you may have heard, lots of ColdFusion powered sites were targeted by hackers using SQL Injection this week.
Fortunately SQL Injection is very easy to prevent in CFML using the
cfqueryparam tag, and many people have pointed out some of the simple use cases for the tag. But there are a few cases where you can't use the
cfqueryparam tag. In those cases, ColdFusion might throw an exception that looks like this:
[Macromedia][SQLServer JDBC Driver][SQLServer]Incorrect syntax near '@P1'. [Macromedia][SQLServer JDBC Driver][SQLServer]Statement(s) could not be prepared.
Let's take a look at some of these special cases, and how to get around them:
If you are passing a variable into a
SELECT TOP statement, you can't use
cfqueryparam, instead consider using the
Val function. This is a really handy function that will return
0 whenever it gets a non-numeric value. The
Val function still allows decimal values, we can convert those to an integer using the
Ceiling function, which rounds up to the nearest integer.
SELECT TOP #Ceiling(Val(url.max_rows))# first_name FROM people
When attempting to use a
cfqueryparam tag in the
ORDER BY statement you might receive an error such as:
[Macromedia][SQLServer JDBC Driver][SQLServer]The SELECT item identified by the ORDER BY number 1 contains a variable as part of the expression identifying a column position. Variables are only allowed when ordering by an expression referencing a column name.
A good way to get around this limitation is to use the
ListFindNoCase function, to limit the sortable column names, for example:
<cfset sortable_column_list = "age,height,weight,first_name"> <cfquery ...> SELECT first_name, age, height, weight FROM people ORDER BY <cfif ListFindNoCase(sortable_column_list, url.sort_column)>#url.sort_column#<cfelse>first_name</cfif> </cfquery>
Passing Value Lists using IN
What to do when your variable contains a list of values to be used with a SQL
IN expression? The
cfqueryparam actually makes it very easy to pass a list, you don't even need to put single quotes around each element if for text lists, it takes care of that for you. To use
cfqueryparam with an
IN simply add
list="true" to your
<cfset name_list = "Bob,Fred,Pete"> <cfquery ...> SELECT first_name, age, height, weight FROM people WHERE first_name IN (<cfqueryparam value="#name_list#" list="true" cfsqltype="cf_sql_varchar">) </cfquery>
ColdFusion 8 now allows
cfqueryparam in cached queries, but if you are running earlier versions, you won't be able to use it with cached queries.
If the variables passed into the query are integer only, then you can use the
Val function to protect against SQL Injection. Or if the possible string values are limited you can use the
ListFindNoCase function as shown above.
The best workaround is to remove the caching, upgrade to CF8, or cache them in the application scope, as follows:
<cfif NOT IsDefined("application.my_cached_query")> <cfquery name="application.my_cached_query"> ... </cfquery> </cfif>
This will keep the query cached until the application is reinitialized, or the variable is overwritten.
cfqueryparam lets you pass
null values into your database using the
null="true" attribute. For example:
UPDATE people SET age = <cfif IsValid("integer", form.age) AND form.age NEQ 0> <cfqueryparam value="#form.age#" cfsqltype="cf_sql_integer"> <cfelse> <cfqueryparam null="true" cfsqltype="cf_sql_integer"> </cfif>
Those are some of the more common gotcha's that you will run into with
cfqueryparam. Please post a comment with any other
cfqueryparam tricks, or special cases.
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Mastering CFQUERYPARAM was first published on July 24, 2008.
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