modulexcite / sqlson

Template-based query language for Node/MySQL

Introduction

sqlson is a prototype template-based query language that simplifies writing database queries in Javascript.

It leverages SQL and Javascript object notation to allow you to re-use what you already know about SQL and Javascript, just together as a declarative template.

sqlson only supports simple queries against MySQL and does not provide any other DML methods like CREATE, UPDATE or DELETE. I may support these in the future, but I'm focusing on just experimenting with the template syntax and the inverse join algorithm for the time being.

Usage

Assume we have the following parent/child MySQL tables defined:

mysql> describe parent;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| text  | varchar(100) | NO   |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+

mysql> describe child;
+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id          | int(11)      | NO   | PRI | NULL    | auto_increment |
| text        | varchar(100) | YES  |     | NULL    |                |
| fk_parentid | int(11)      | NO   | MUL | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

We'd like to query this data such that we end up with a tree of JS objects containing the parent object along with its children, something like the following:

{
    "id": 1, 
    "text":"this is the parent",
    "children": [ { 
        "id":1, 
        "text":"this is the first child"
    }, { 
        "id":2, 
        "text":"this is the second child"
    } ]
}

We can write this as a query object by generalizing it and inserting some SQL strings:

var query = [ 
    "parent", "parent.id = 1", { 
        "id":"id", 
        "text":"text",
        "children": [ 
            "child", "child.fk_parentid = parent.id", { 
                "id":"id", 
                "text":"text"
            } 
        ]
    } 
];

A query specification is a set of nested JS arrays with the table name, the SQL WHERE clause and an object template that maps the field names to JS object attributes. The object tempate consists of a map between the desired output field identifiers and the field names in the SQL schema. The SQL schema identifiers must match those of the target schema but the keys may be named as desired except as described below.

"parent" and "child" in the above example are literally the table names as defined in the database schema. The "children" property is used internally to identify the subquery. This field must be named exactly as shown above. In future version we may be able to detect that this collection represents the related records in some other way. Otherwise, property names for the resulting object graph may be named using any valid javascript identifiers.

Note that when converting from tuples to javascript objects we perform a map reduce process that relies on the "id" property of the children to merge the final result set. This field must be called "id". Hopefully this can be relaxed in the future.

We can use sqlson to generate the sql required to perform the query and disjoin the resulting recordset.

The following code example shows how to use the node mysql client to query data and output the results as JSON:

var sql = genSql( query ); 
client.query(
	sql, [], 
	function( err, results ) { 
		console.log( results );
		console.log( JSON.stringify( disjoin( query, results ), null, 4 ) );
		client.end();
	}
);

Status

sqlson is a proof of concept currently. It isn't meant for production, and it isn't complete. The basics have been implemented, but have not been optimized. The initial goal is to come up with a useful query format.

Development

Create a test MySql database using createdb.sh. Run the tests using expresso The server component uses Express. Integration tests require MySQL and the node.js mysql library

Limitations

Can't perform self-joins due to lack of aliases in the generated sql.

License

MIT License, copyright 2012 Dan Newcome