Difference between revisions of "SQL Module"

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The SQL Module contains [[Querying#Functions|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 <code>sql</code> prefix, which is linked to the <code><nowiki>http://www.basex.org/sql</nowiki></code> namespace. The module will be officially supported with the upcoming {{Version|7.0}} of BaseX.
+
This [[Module Library|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 {{Code|lib}} directory. To connect to MySQL, for example, download the [https://dev.mysql.com/downloads/connector/j/ Connector/J Driver] and extract the archive into this directory.
 +
 
 +
=Conventions=
 +
 
 +
All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/sql</nowiki></code> namespace, which is statically bound to the {{Code|sql}} prefix.<br/>
 +
 
 +
=Functions=
  
 
==sql:init==
 
==sql:init==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:init</b>($class as xs:string) as empty-sequence()</code>
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:init|$class as xs:string|empty-sequence()}}
| valign='top' | '''Summary'''
+
|- valign="top"
|This function initializes a JDBC driver specified via <code>$class</code>. This step might be superfluous if the SQL database is not embedded.<br/ >
+
| '''Summary'''
|-
+
|This function initializes a JDBC driver specified via {{Code|$class}}. This step might be superfluous if the SQL database is not embedded.<br/ >
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0007]]</b> is raised if the specified driver class is not found.
+
| '''Errors'''
 +
|{{Error|init|#Errors}} the specified driver is not found.
 
|}
 
|}
  
 
==sql:connect==
 
==sql:connect==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:connect</b>($url as xs:string) as xs:int</code><br/ ><code><b>sql:connect</b>($url as xs:string, $user as xs:string, $password as xs:string) as xs:int</code><br/ ><code><b>sql:connect</b>($url as xs:string, $user as xs:string, $password as xs:string, $options as xs:item()) as xs:int</code><br/ >
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:connect|$url as xs:string|xs:anyURI}}<br/ >{{Func|sql:connect|$url as xs:string, $user as xs:string, $password as xs:string|xs:anyURI}}<br/ >{{Func|sql:connect|$url as xs:string, $user as xs:string, $password as xs:string, $options as map(*)?|xs:anyURI}}<br/ >
| valign='top' | '''Summary'''
+
|- valign="top"
|This function establishes a connection to a relational database. As a result a connection handle is returned. The parameter <code>$url</code> is the URL of the database and shall be of the form: <code>jdbc:<driver name>:[//<server>[/<database>]</code>. If the parameters <code>$user</code> and <code>$password</code> are specified, they are used as credentials for connecting to the database. The parameter <code>$options</code> can be used to set connection options, e.g. auto-commit mode. It can be specified as:
+
| '''Summary'''
* <code>element(sql:options):</code> <code>&lt;sql:options/&gt;</code> must be used as root element, and the options are specified as child nodes, with the element name representing the key and the text node representing the value:<br /
+
|This function establishes a connection to a relational database and returns a connection id. The parameter {{Code|$url}} is the URL of the database and shall be of the form: {{Code|jdbc:<driver name>:[//<server>[/<database>]]}}. If the parameters {{Code|$user}} and {{Code|$password}} are specified, they are used as credentials for connecting to the database. The {{Code|$options}} parameter can be used to set connection options.
/><code>&lt;sql:options&gt;<br/>&nbsp;&nbsp;&lt;sql:autocommit&gt;true&lt;/sql:autocommit&gt;<br/>&nbsp;&nbsp;...<br/>&lt;/sql:options&gt;</code>
+
|- valign="top"
* [[Map_Functions|map structure]]: all options can be directly represented as key/value pairs:<br /><code>map { "autocommit" := "true", ... </code>}<br/>
+
| '''Errors'''
|-
+
|{{Error|error|#Errors}} an SQL exception occurred when connecting to the database.
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs, e.g. missing JDBC driver or not existing relation.
+
| '''Examples'''
 +
|Connects to an SQL Server and sets autocommit to {{Code|true}}:
 +
<syntaxhighlight lang="xquery">
 +
sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })
 +
</syntaxhighlight>
 
|}
 
|}
  
 
==sql:execute==
 
==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.
 
  
{|
+
{| width='100%'
|-
+
|- valign="top"
| valign='top' width='90' | '''Signatures'''
+
| width='120' | '''Signatures'''
|<code><b>sql:execute</b>($connection as xs:int, $item as xs:item) as element()*</code>
+
|{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string|item()*}}<br/>{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string, $options as map(*)?|item()*}}
|-
+
|- valign="top"
| valign='top' | '''Summary'''
+
| '''Summary'''
| This function executes a query, update or prepared statement. The parameter <code>$id</code> specifies either a connection handle or a prepared statement handle. The parameter <code>$item</code> is either a string representing an SQL statement or an element <code><sql:parameters/></code> representing the parameters for a prepared statement along with their types and values. In case of the latter, the following schema shall be used:<br/ >
+
| This function executes an SQL {{Code|$statement}}, using the connection with the specified {{Code|$id}}. The returned result depends on the kind of statement:
<pre class="brush:xml">
+
* If an update statement was executed, the number of updated rows will be returned as integer.
 +
* Otherwise, an XML representation of all results will be returned.
 +
With {{Code|$options}}, the following parameter can be set:
 +
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 +
|- valign="top"
 +
| '''Errors'''
 +
|{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/>{{Error|timeout|#Errors}} query execution exceeded timeout.<br/>
 +
|}
 +
 
 +
==sql:execute-prepared==
 +
 
 +
{| width='100%'
 +
|- valign="top"
 +
| width='120' | '''Signatures'''
 +
|{{Func|sql:execute-prepared|$id as xs:anyURI, $params as element(sql:parameters)|item()*}}<br/>{{Func|sql:execute-prepared|$id as xs:anyURI, $params as element(sql:parameters), $options as map(*)?|item()*}}
 +
|- valign="top"
 +
| '''Summary'''
 +
| This function executes a prepared statement with the specified {{Code|$id}}. The output format is identical to {{Function||sql:execute}}. The optional parameter {{Code|$params}} is an element {{Code|<sql:parameters/>}} representing the parameters for a prepared statement along with their types and values. The following schema shall be used:<br/ >
 +
<syntaxhighlight lang="xquery">
 
element sql:parameters {
 
element sql:parameters {
element sql:parameter {
+
  element sql:parameter {
  attribute type { "int"|"string"|"boolean"|"date"|"double"|"float"|"short"|"time"|"timestamp" },
+
    attribute type { "bigdecimal" | "boolean" | "byte" | "date" | "double" | "float" |
  attribute null { "true"|"false" }?,
+
      "int" | "long" | "short" | "sqlxml" | "string" | "time" | "timestamp" },
   text }+ }?
+
    attribute null { "true" | "false" }?,
</pre>
+
    text
|-
+
   }+
| valign='top' | '''Errors'''
+
}?
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs, e.g. not existing relation is retrieved.<br/ >
+
</syntaxhighlight>
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0002]]</b> is raised if a wrong connection handle or prepared statement handle is passed.<br/ >
+
With {{Code|$options}}, the following parameter can be set:
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0003]]</b> is raised if the number of <code><sql:parameter/></code> elements in <code><sql:parameters/></code> differs from the number of placeholders in the prepared statement.<br/ >
+
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0004]]</b> is raised if the type of a parameter for a prepared statement is not specified.<br/ >
+
|- valign="top"
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0005]]</b> is raised if an attribute different from <code>type</code> and <code>null</code> is set for a <code><sql:parameter/></code> element.<br/ >
+
| '''Errors'''
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0006]]</b> is raised if a parameter is from type date, time or timestamp and its value is in an invalid format.<br/ >
+
|{{Error|attribute|#Errors}} an attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|<sql:parameter/>}} element.<br/ >{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/ >{{Error|parameters|#Errors}} no parameter type specified.<br/>{{Error|timeout|#Errors}} query execution exceeded timeout.<br/>{{Error|type|#Errors}} the value of a parameter cannot be converted to the specified format.
 
|}
 
|}
  
 
==sql:prepare==
 
==sql:prepare==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:prepare</b>($connection as xs:int, $statement as xs:string) as xs:int</code>
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:prepare|$id as xs:anyURI, $statement as xs:string|xs:anyURI}}
| valign='top' | '''Summary'''
+
|- valign="top"
|This function prepares a statement and returns a handle to it. The parameter <code>$connection</code> indicates the connection handle to be used. The parameter <code>$statement</code> is a string representing an SQL statement with one or more '?' placeholders. If the value of a field has to be set to <code>NULL</code>, then the attribute <code>null</code> of the element <code><sql:parameter/></code> has to be <code>true</code>.
+
| '''Summary'''
|-
+
|This function prepares an SQL {{Code|$statement}}, using the specified connection {{Code|$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 {{Code|NULL}}, then the attribute {{Code|null}} of the {{Code|<sql:parameter/>}} element must be {{Code|true}}.
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs.<br/ >
+
| '''Errors'''
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0002]]</b> is raised if a wrong connection handle is passed.<br/ >
+
|{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/ >
 
|}
 
|}
  
 
==sql:commit==
 
==sql:commit==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:commit</b>($connection as xs:int) as xs:element?</code>
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:commit|$id as xs:anyURI|empty-sequence()}}
| valign='top' | '''Summary'''
+
|- valign="top"
| This function commits the changes made to a relational database. <code>$connection</code> specifies the connection handle.
+
| '''Summary'''
|-
+
| This function commits the changes made to a relational database, using the specified connection {{Code|$id}}.
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs.<br/ >
+
| '''Errors'''
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0002]]</b> is raised if a wrong connection handle is passed.<br/ >
+
|{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/ >
 
|}
 
|}
  
 
==sql:rollback==
 
==sql:rollback==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:rollback</b>($connection as xs:int) as xs:element?</code>
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:rollback|$id as xs:anyURI|empty-sequence()}}
| valign='top' | '''Summary'''
+
|- valign="top"
| This function rolls back the changes made to a relational database. <code>$connection</code> specifies the connection handle.
+
| '''Summary'''
|-
+
| This function rolls back the changes made to a relational database, using the specified connection {{Code|$id}}.
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs.<br/ >
+
| '''Errors'''
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0002]]</b> is raised if a wrong connection handle is passed.<br/ >
+
|{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/ >
 
|}
 
|}
  
 
==sql:close==
 
==sql:close==
{|
+
 
|-
+
{| width='100%'
| valign='top' width='90' | '''Signatures'''
+
|- valign="top"
|<code><b>sql:close</b>($connection as xs:int) as xs:element?</code>
+
| width='120' | '''Signatures'''
|-
+
|{{Func|sql:close|$id as xs:anyURI|empty-sequence()}}
| valign='top' | '''Summary'''
+
|- valign="top"
| This function closes a connection to a relational database. <code>$connection</code> specifies the connection handle.
+
| '''Summary'''
|-
+
| This function closes a database connection with the specified {{Code|$id}}.<br/>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.
| valign='top' | '''Errors'''
+
|- valign="top"
|<b>[[XQuery Errors#SQL Functions Errors|FOSQ0001]]</b> is raised if an SQL exception occurs.<br/ >
+
| '''Errors'''
<b>[[XQuery Errors#SQL Functions Errors|FOSQ0002]]</b> is raised if a wrong connection handle is passed.<br/ >
+
|{{Error|error|#Errors}} an error occurred while executing SQL.<br/ >{{Error|id|#Errors}} the specified connection does not exist.<br/ >
 
|}
 
|}
  
==Examples==
+
=Examples=
  
===Direct queries===
+
==Direct queries==
A simple select statement can be executed on the following way:
 
  
<pre class="brush:xquery">
+
A simple select statement can be executed as follows:
let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
+
 
return sql:execute($conn, "SELECT * FROM coffees WHERE price < 10")
+
<syntaxhighlight lang="xquery">
</pre>
+
let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 +
return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")
 +
</syntaxhighlight>
  
The result will look like:
+
The result may look like:
  
<pre class="brush:xml">
+
<syntaxhighlight lang="xml">
<sql:row xmlns:sql="http://www.basex.org/sql">
+
<sql:row xmlns:sql="http://basex.org/modules/sql">
 
   <sql:column name="cof_name">French_Roast</sql:column>
 
   <sql:column name="cof_name">French_Roast</sql:column>
 
   <sql:column name="sup_id">49</sql:column>
 
   <sql:column name="sup_id">49</sql:column>
   <sql:column name="price">9.5</sql:column>
+
   <sql:column name="price">3.5</sql:column>
 
   <sql:column name="sales">15</sql:column>
 
   <sql:column name="sales">15</sql:column>
 
   <sql:column name="total">30</sql:column>
 
   <sql:column name="total">30</sql:column>
 
</sql:row>
 
</sql:row>
<sql:row xmlns:sql="http://www.basex.org/sql">
+
<sql:row xmlns:sql="http://basex.org/modules/sql">
 
   <sql:column name="cof_name">French_Roast_Decaf</sql:column>
 
   <sql:column name="cof_name">French_Roast_Decaf</sql:column>
 
   <sql:column name="sup_id">49</sql:column>
 
   <sql:column name="sup_id">49</sql:column>
Line 140: Line 171:
 
   <sql:column name="total">14</sql:column>
 
   <sql:column name="total">14</sql:column>
 
</sql:row>
 
</sql:row>
<sql:row xmlns:sql="http://www.basex.org/sql">
+
</syntaxhighlight>
  <sql:column name="cof_name">Colombian_Decaf</sql:column>
+
 
  <sql:column name="sup_id">101</sql:column>
+
==Prepared Statements==
  <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>
 
</pre>
 
  
===Prepared Statements===
 
 
A prepared select statement can be executed in the following way:
 
A prepared select statement can be executed in the following way:
  
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
 
(: Establish a connection :)
 
(: Establish a connection :)
 
let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 
let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
Line 160: Line 184:
 
(: Values and types of prepared statement parameters :)
 
(: Values and types of prepared statement parameters :)
 
let $params := <sql:parameters>
 
let $params := <sql:parameters>
                <sql:parameter type='double'>10</sql:parameter>
+
                <sql:parameter type='double'>10</sql:parameter>
                <sql:parameter type='string'>French_Roast</sql:parameter>
+
                <sql:parameter type='string'>French_Roast</sql:parameter>
 
               </sql:parameters>
 
               </sql:parameters>
 
(: Execute prepared statement :)
 
(: Execute prepared statement :)
return sql:execute($prep, $params)
+
return sql:execute-prepared($prep, $params)
</pre>
+
</syntaxhighlight>
 +
 
 +
==SQLite==
 +
 
 +
The following expression demonstrates how SQLite can be addressed with the [https://bitbucket.org/xerial/sqlite-jdbc/ Xerial SQLite JDBC driver]:
 +
 
 +
<syntaxhighlight lang="xquery">
 +
(: 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")
 +
)
 +
</syntaxhighlight>
 +
 
 +
=Errors=
 +
 
 +
{| class="wikitable" width="100%"
 +
! width="110"|Code
 +
|Description
 +
|- valign="top"
 +
|{{Code|attribute}}
 +
|An attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|&lt;sql:parameter/&gt;}} element.
 +
|- valign="top"
 +
|{{Code|error}}
 +
|An SQL exception occurred.
 +
|- valign="top"
 +
|{{Code|id}}
 +
|A connection does not exist.
 +
|- valign="top"
 +
|{{Code|init}}
 +
|A database driver is not found.
 +
|- valign="top"
 +
|{{Code|parameters}}
 +
|No parameter type specified.
 +
|- valign="top"
 +
|{{Code|timeout}}
 +
|Query execution exceeded timeout.
 +
|- valign="top"
 +
|{{Code|type}}
 +
|The value of a parameter cannot be converted to the specified format.
 +
|}
 +
 
 +
=Changelog=
 +
 
 +
;Version 9.6
 +
* Updated: {{Function||sql:execute-prepared}}, additional types added
 +
 
 +
;Version 9.0
 +
* Updated: {{Function||sql:execute}}, {{Function||sql:execute-prepared}}: Return update count for updating statements. {{Code|$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 {{Function||sql:execute-prepared}}
 +
 
 +
The module was introduced with Version 7.0.

Latest revision as of 14:19, 20 July 2022

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.

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]

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 init: the specified driver is not found.

sql:connect[edit]

Signatures sql:connect($url as xs:string) as xs:anyURI
sql:connect($url as xs:string, $user as xs:string, $password as xs:string) as xs:anyURI
sql:connect($url as xs:string, $user as xs:string, $password as xs:string, $options as 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>]. If the parameters $user and $password are specified, they 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]

Signatures sql:execute($id as xs:anyURI, $statement as xs:string) as item()*
sql:execute($id as xs:anyURI, $statement as xs:string, $options as 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:
  • If an update statement was executed, the number of updated rows will be returned as integer.
  • Otherwise, an XML representation of all results will be returned.

With $options, the following parameter can be set:

  • timeout: query execution will be interrupted after the specified number of seconds.
Errors error: an error occurred while executing SQL.
id: the specified connection does not exist.
timeout: query execution exceeded timeout.

sql:execute-prepared[edit]

Signatures sql:execute-prepared($id as xs:anyURI, $params as element(sql:parameters)) as item()*
sql:execute-prepared($id as xs:anyURI, $params as element(sql:parameters), $options as 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 $options, the following parameter can be set:

  • timeout: query execution will be interrupted after the specified number of seconds.
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]

Signatures 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]

Signatures 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]

Signatures 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]

Signatures 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 9.6
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

The module was introduced with Version 7.0.