SQL Module

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The SQL Module contains XQuery functions to access relational databases from XQuery using SQL. With this module, you can execute query, update and prepared statements, and the result sets are returned as sequences of XML elements representing tuples. Each element has children representing the columns returned by the SQL statement. All functions dealing with access to relational databases use the sql prefix, which is linked to the http://www.basex.org/sql namespace. The module will be officially supported with the upcoming Version 7.0 of BaseX.

sql:init

Signatures sql:init($class as xs:string) as empty-sequence()
Summary This function initializes a JDBC driver specified via $class. This step might be superfluous if the SQL database is not embedded.
Errors FOSQ0007 is raised if the specified driver class is not found.

sql:connect

Signatures sql:connect($url as xs:string) as xs:int
sql:connect($url as xs:string, $user as xs:string, $password as xs:string) as xs:int
sql:connect($url as xs:string, $user as xs:string, $password as xs:string, $options as xs:item()) as xs:int
Summary This function establishes a connection to a relational database. As a result a connection handle is returned. The parameter $url is the URL of the database and shall be of the form: jdbc:<driver name>:<server> [/<database>. If the parameters $user and $password are specified, they are used as credentials for connecting to the database. The parameter $options can be used to set connection options, e.g. auto-commit mode. It can be specified as:
  • element(sql:options): <sql:options/> must be used as root element, and the options are specified as child nodes, with the element name representing the key and the text node representing the value:
    <sql:options>
      <sql:autocommit>true</sql:autocommit>
      ...
    </sql:options>
  • map structure: all options can be directly represented as key/value pairs:
    map { "autocommit" := "true", ... }
Errors FOSQ0001 is raised if an SQL exception occurs, e.g. missing JDBC driver or not existing relation.

sql:execute

Once a connection is established, the returned connection handle can be used to execute queries on the database. Our SQL module supports both direct queries and prepared statements.

Signatures sql:execute($connection as xs:int, $item as xs:item) as element()*
Summary This function executes a query, update or prepared statement. The parameter $id specifies either a connection handle or a prepared statement handle. The parameter $item is either a string representing an SQL statement or an element <sql:parameters/> representing the parameters for a prepared statement along with their types and values. In case of the latter, the following schema shall be used:
element sql:parameters {
 element sql:parameter {
  attribute type { "int"|"string"|"boolean"|"date"|"double"|"float"|"short"|"time"|"timestamp" },
  attribute null { "true"|"false" }?,
  text }+ }?
Errors FOSQ0001 is raised if an SQL exception occurs, e.g. not existing relation is retrieved.

FOSQ0002 is raised if a wrong connection handle or prepared statement handle is passed.
FOSQ0003 is raised if the number of <sql:parameter/> elements in <sql:parameters/> differs from the number of placeholders in the prepared statement.
FOSQ0004 is raised if the type of a parameter for a prepared statement is not specified.
FOSQ0005 is raised if an attribute different from type and null is set for a <sql:parameter/> element.
FOSQ0006 is raised if a parameter is from type date, time or timestamp and its value is in an invalid format.

sql:prepare

Signatures sql:prepare($connection as xs:int, $statement as xs:string) as xs:int
Summary This function prepares a statement and returns a handle to it. The parameter $connection indicates the connection handle to be used. The parameter $statement is a string representing an SQL statement with one or more '?' placeholders. If the value of a field has to be set to NULL, then the attribute null of the element <sql:parameter/> has to be true.
Errors FOSQ0001 is raised if an SQL exception occurs.

FOSQ0002 is raised if a wrong connection handle is passed.

sql:commit

Signatures sql:commit($connection as xs:int) as xs:element?
Summary This function commits the changes made to a relational database. $connection specifies the connection handle.
Errors FOSQ0001 is raised if an SQL exception occurs.

FOSQ0002 is raised if a wrong connection handle is passed.

sql:rollback

Signatures sql:rollback($connection as xs:int) as xs:element?
Summary This function rolls back the changes made to a relational database. $connection specifies the connection handle.
Errors FOSQ0001 is raised if an SQL exception occurs.

FOSQ0002 is raised if a wrong connection handle is passed.

sql:close

Signatures sql:close($connection as xs:int) as xs:element?
Summary This function closes a connection to a relational database. $connection specifies the connection handle.
Errors FOSQ0001 is raised if an SQL exception occurs.

FOSQ0002 is raised if a wrong connection handle is passed.

Examples

Direct queries

A simple select statement can be executed on the following way:

let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
return sql:execute($conn, "SELECT * FROM coffees WHERE price < 10")

The result will look like:

<sql:row xmlns:sql="http://www.basex.org/sql">
  <sql:column name="cof_name">French_Roast</sql:column>
  <sql:column name="sup_id">49</sql:column>
  <sql:column name="price">9.5</sql:column>
  <sql:column name="sales">15</sql:column>
  <sql:column name="total">30</sql:column>
</sql:row>
<sql:row xmlns:sql="http://www.basex.org/sql">
  <sql:column name="cof_name">French_Roast_Decaf</sql:column>
  <sql:column name="sup_id">49</sql:column>
  <sql:column name="price">7.5</sql:column>
  <sql:column name="sales">10</sql:column>
  <sql:column name="total">14</sql:column>
</sql:row>
<sql:row xmlns:sql="http://www.basex.org/sql">
  <sql:column name="cof_name">Colombian_Decaf</sql:column>
  <sql:column name="sup_id">101</sql:column>
  <sql:column name="price">8.75</sql:column>
  <sql:column name="sales">6</sql:column>
  <sql:column name="total">12</sql:column>
  <sql:column name="date">2010-10-10 13:56:11.0</sql:column>
</sql:row>

Prepared Statements

A prepared select statement can be executed in the following way:

(: Establish a connection :)
let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
(: Obtain a handle to a prepared statement :)
let $prep := sql:prepare($conn, "SELECT * FROM coffees WHERE price < ? AND cof_name = ?")
(: Values and types of prepared statement parameters :)
let $params := <sql:parameters>
                <sql:parameter type='double'>10</sql:parameter>
                <sql:parameter type='string'>French_Roast</sql:parameter>
               </sql:parameters>
(: Execute prepared statement :)
return sql:execute($prep, $params)