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Comments on Section 4.11.2 Databases and 4.11.3 Executing SQL statements

From: Ben Meadowcroft <ben@benmeadowcroft.com>
Date: Sat, 1 Mar 2008 10:24:06 -0000
To: <public-html@w3.org>
Message-ID: <003f01c87b86$64accee0$0202a8c0@benspc>

I've got a couple of comments on section "4.11.2 Databases" and "4.11.3
Executing SQL statements".

Comment on "4.11.2 Databases"
This section states "The transaction() method takes one or two arguments."
yet the interface defined above this statement shows that 3 arguments can be
provided.

Comment on "4.11.3 Executing SQL statements"
I would like to suggest adding support for named parameters when executing
SQL (in addition to the current array mechanism). My proposal is that we
allow named placeholders in the SQL statement and then allow an object to be
passed as a parameter, replacing the placeholder with the value of the
matching named object property.

A specific example would be:
transaction.executeSql(
   "SELECT * from employee WHERE employee.firstname = :firstname AND
employee.salary < :salary;",
   {"firstname" : "Ben", "salary" : 999.99},
   callback
);

I've used the Java Persistence API and Hibernate style of named parameters,
along with a more common JavaScript idiom of using an object as an
associative array.

I think the introduction of named parameters would help reduce the
programming errors that occur when dealing with arrays and the implicit
parameter ordering that this requires. Another advantage is that
applications could reuse objects in use as query parameters rather than
mapping them to an array (in the right order!). For example:

transaction.executeSql(
   "SELECT * from departent WHERE department.name = ? AND
department.location = ?;",
   [employee.department, employee.location],
   callback
);

Would be:

transaction.executeSql(
   "SELECT * from departent WHERE department.name = :department AND
department.location = :location;",
   employee,
   callback
);

The mapping would be fairly simple and could be mapped onto the existing
array specification if required, e.g.:
1. take the SQL string and extracting any named parameters into an array,
replacing them with the '?' placeholder
2. iterate over the array, take then name of the parameter and look up its
property value on the object passed in, replace the parameter name in the
array with the retrieved value.
3. continue processing with the modified SQL string (with ? placeholders)
and an array of parameters.

What are peoples thoughts on these suggestions?

-- 
Ben Meadowcroft
http://www.benmeadowcroft.com/
Received on Saturday, 1 March 2008 10:24:37 GMT

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