SQL Module
This XQuery Module contains 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.
This module uses JDBC to connect to a SQL server. Hence, your JDBC driver will need to be added to the classpath, too. If you work with the full distributions of BaseX, you can copy the driver into the lib
directory. To connect to MySQL, for example, download the Connector/J Driver and extract the archive into this directory.
Contents
Conventions[edit]
All functions and errors in this module are assigned to the http://basex.org/modules/sql
namespace, which is statically bound to the sql
prefix.
Functions[edit]
sql:init[edit]
Signature | 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 | init : the specified driver is not found.
|
sql:connect[edit]
Updated with Version 11: Optional credentials.
Signature | sql:connect( $url as xs:string, $options as map(*)? := map { } ) as xs:anyURI |
Summary | This function establishes a connection to a relational database and returns a connection id. The parameter $url is the URL of the database and shall be of the form: jdbc:<driver name>:<server> [/<database>] . Values specified for $username and $password are used as credentials for connecting to the database. The $options parameter can be used to set connection options.
|
Errors | error : an SQL exception occurred when connecting to the database.
|
Examples | Connects to an SQL Server and sets autocommit to true :
sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })
|
sql:execute[edit]
Signature | sql:execute( $id as xs:anyURI, $statement as xs:string, $options as map(*)? := map { } ) as item()* |
Summary | This function executes an SQL $statement , using the connection with the specified $id . The returned result depends on the kind of statement:
With
|
Errors | error : an error occurred while executing SQL.id : the specified connection does not exist.timeout : query execution exceeded timeout. |
sql:execute-prepared[edit]
Signature | sql:execute-prepared( $id as xs:anyURI, $params as element(sql:parameters), $options as map(*)? := map { } ) as item()* |
Summary | This function executes a prepared statement with the specified $id . The output format is identical to sql:execute . The optional parameter $params is an element <sql:parameters/> representing the parameters for a prepared statement along with their types and values. The following schema shall be used:element sql:parameters {
element sql:parameter {
attribute type { "bigdecimal" | "boolean" | "byte" | "date" | "double" | "float" |
"int" | "long" | "short" | "sqlxml" | "string" | "time" | "timestamp" },
attribute null { "true" | "false" }?,
text
}+
}?
With
|
Errors | attribute : an attribute different from type and null is set for a <sql:parameter/> element.error : an error occurred while executing SQL.id : the specified connection does not exist.parameters : no parameter type specified.timeout : query execution exceeded timeout.type : the value of a parameter cannot be converted to the specified format.
|
sql:prepare[edit]
Signature | sql:prepare( $id as xs:anyURI, $statement as xs:string ) as xs:anyURI |
Summary | This function prepares an SQL $statement , using the specified connection $id , and returns the id reference to this statement. The statement is a string with one or more '?' placeholders. If the value of a field has to be set to NULL , then the attribute null of the <sql:parameter/> element must be true .
|
Errors | error : an error occurred while executing SQL.id : the specified connection does not exist. |
sql:commit[edit]
Signature | sql:commit( $id as xs:anyURI ) as empty-sequence() |
Summary | This function commits the changes made to a relational database, using the specified connection $id .
|
Errors | error : an error occurred while executing SQL.id : the specified connection does not exist. |
sql:rollback[edit]
Signature | sql:rollback( $id as xs:anyURI ) as empty-sequence() |
Summary | This function rolls back the changes made to a relational database, using the specified connection $id .
|
Errors | error : an error occurred while executing SQL.id : the specified connection does not exist. |
sql:close[edit]
Signature | sql:close( $id as xs:anyURI ) as empty-sequence() |
Summary | This function closes a database connection with the specified $id .Opened connections will automatically be closed after the XQuery expression has been evaluated, but in order to save memory, it is always recommendable to close connections that are not used anymore. |
Errors | error : an error occurred while executing SQL.id : the specified connection does not exist. |
Examples[edit]
Direct queries[edit]
A simple select statement can be executed as follows:
let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")
The result may look like:
<sql:row xmlns:sql="http://basex.org/modules/sql">
<sql:column name="cof_name">French_Roast</sql:column>
<sql:column name="sup_id">49</sql:column>
<sql:column name="price">3.5</sql:column>
<sql:column name="sales">15</sql:column>
<sql:column name="total">30</sql:column>
</sql:row>
<sql:row xmlns:sql="http://basex.org/modules/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>
Prepared Statements[edit]
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 $params := <sql:parameters>
<sql:parameter type='double'>10</sql:parameter>
<sql:parameter type='string'>French_Roast</sql:parameter>
</sql:parameters>
(: Execute prepared statement :)
return sql:execute-prepared($prep, $params)
SQLite[edit]
The following expression demonstrates how SQLite can be addressed with the Xerial SQLite JDBC driver:
(: Initialize driver :)
sql:init("org.sqlite.JDBC"),
(: Establish a connection :)
let $conn := sql:connect("jdbc:sqlite:database.db")
return (
(: Create a new table :)
sql:execute($conn, "drop table if exists person"),
sql:execute($conn, "create table person (id integer, name string)"),
(: Run 10 updates :)
for $i in 1 to 10
let $q := "insert into person values(" || $i || ", '" || $i || "')"
return sql:execute($conn, $q),
(: Return table contents :)
sql:execute($conn, "select * from person")
)
Errors[edit]
Code | Description |
---|---|
attribute
|
An attribute different from type and null is set for a <sql:parameter/> element.
|
error
|
An SQL exception occurred. |
id
|
A connection does not exist. |
init
|
A database driver is not found. |
parameters
|
No parameter type specified. |
timeout
|
Query execution exceeded timeout. |
type
|
The value of a parameter cannot be converted to the specified format. |
Changelog[edit]
- Version 11
- Updated:
sql:connect
: Optional credentials.
- Version 9.6
- Updated:
sql:execute-prepared
, additional types added
- Version 9.0
- Updated:
sql:execute
,sql:execute-prepared
: Return update count for updating statements.$options
argument added. - Updated: Connection ids are URIs now.
- Updated: error codes updated; errors now use the module namespace
- Version 7.5
- Updated: prepared statements are now executed via
sql:execute-prepared
The module was introduced with Version 7.0.