Verifies the data type of a query parameter and, for DBMSs that support bind variables, enables ColdFusion to use bind variables in the SQL statement. Bind variable usage enhances performance when executing a cfquery statement multiple times.

This tag is nested within a cfquery tag, embedded in a query SQL statement. If you specify optional parameters, this tag performs data validation.

Macromedia recommends that you use the cfqueryparam tag within every cfquery tag, to help secure your databases from unauthorized users. For more information, see Security Bulletin ASB99-04, "Multiple SQL Statements in Dynamic Queries," at www.macromedia.com/devnet/security/security_zone/asb99-04.html, and Chapter 20, "Accessing and Retrieving Data" in ColdFusion MX Developer's Guide.

Database manipulation tags

cfinsert, cfprocparam, cfprocresult, cfquery, cfstoredproc, cftransaction, cfupdate; "Enhancing security with cfqueryparam" in Chapter 20, "Accessing and Retrieving Data," in ColdFusion MX Developer's Guide

Use the cfqueryparam tag in any SQL statement (for example, SELECT, INSERT, UPDATE, and DELETE) that uses ColdFusion variables.

You cannot use the cfquery cachedAfter or cachedWithin attributes with cfqueryparam.

For maximum validation of string data, specify the maxlength attribute.

This tag does the following:

• Allows the use of SQL bind parameters, which improves performance.
• Ensures that variable data matches the specified SQL type.
• Allows long text fields to be updated from a SQL statement.
• Escapes string variables in single-quotation marks.

To benefit from the enhanced performance of bind variables, you must use cfqueryparam for all ColdFusion variables, and your DBMS must support bind variables. If a DBMS does not support bind parameters, ColdFusion validates and substitutes the validated parameter value back into the string. If validation fails, it returns an error message.

The validation rules are as follows:

• For these types, a data value can be converted to a numeric value: CF_SQL_SMALLINT, CF_SQL_INTEGER, CF_SQL_REAL, CF_SQL_FLOAT, CF_SQL_DOUBLE, CF_SQL_TINYINT, CF_SQL_MONEY, CF_SQL_MONEY4, CF_SQL_DECIMAL, CF_SQL_NUMERIC, and CF_SQL_BIGINT
• For these types, a data value can be converted to a date supported by the target data source: CF_SQL_DATE, CF_SQL_TIME, CF_SQL_TIMESTAMP
• For all other types, if the maxLength attribute is used, a data value cannot exceed the maximum length specified.

ColdFusion debug output shows the bind variables as question marks and lists the values beneath the query, in order of usage.

The following table shows the mapping of ColdFusion SQL data types with JDBC SQL types and those of the listed database management systems:

<!--- This example shows cfqueryparam with VALID input in Course_ID. --->
<h3>cfqueryparam Example</h3>
<cfset Course_ID = 12>
<cfquery name = "getFirst" dataSource = "cfdocexamples">
   SELECT * 
   FROM courses
   WHERE Course_ID = <cfqueryPARAM value = "#Course_ID#"
   CFSQLType = "CF_SQL_INTEGER"> 
</cfquery>
<cfoutput query = "getFirst">
   <p>Course Number: #Course_ID#<br> Description: #descript#</p>
</cfoutput>

<!--- This example shows the use of CFQUERYPARAM when INVALID string data is
   in Course_ID. ----> 
<p>This example throws an error because the value passed in the CFQUERYPARAM 
tag exceeds the MAXLENGTH attribute</p> 

<cfset LastName="Peterson; DELETE employees WHERE LastName='Peterson'">
<!------- Note that for string input you must specify the MAXLENGTH attribute 
   for validation. --------------------------------------------------> 
<cfquery 
   name="getFirst" datasource="cfdocexamples"> 
   SELECT * 
   FROM employees 
   WHERE LastName=<cfqueryparam 
                        value="#LastName#" 
                        cfsqltype="CF_SQL_VARCHAR" 
                        maxlength="17"> 
</cfquery> 
<cfoutput 
   query="getFirst">       <p>
      Course Number: #FirstName# #LastName# 
      Description: #Department# </p> 
</cfoutput>