Difference between revisions of "SQL Module"

From BaseX Documentation
Jump to navigation Jump to search
(3 intermediate revisions by the same user not shown)
Line 4: Line 4:
  
 
=Conventions=
 
=Conventions=
 
{{Mark|Updated with Version 9.0:}}
 
  
 
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/>
 
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/>
Line 40: Line 38:
 
| '''Examples'''
 
| '''Examples'''
 
|Connects to an SQL Server and sets autocommit to {{Code|true}}:
 
|Connects to an SQL Server and sets autocommit to {{Code|true}}:
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
 
sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })
 
sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })
</pre>
+
</syntaxhighlight>
 
|}
 
|}
  
 
==sql:execute==
 
==sql:execute==
 
{{Mark|Updated with Version 9.0:}} Return update count for updating statements. {{Code|$options}} argument added.
 
  
 
{| width='100%'
 
{| width='100%'
Line 66: Line 62:
  
 
==sql:execute-prepared==
 
==sql:execute-prepared==
 
{{Mark|Updated with Version 9.0:}} Return update count for updating statements.
 
  
 
{| width='100%'
 
{| width='100%'
Line 76: Line 70:
 
| '''Summary'''
 
| '''Summary'''
 
| This function executes a prepared statement with the specified {{Code|$id}}. The output format is identical to [[#sql:execute|sql:execute]]. The optional parameter {{Code|$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/ >
 
| This function executes a prepared statement with the specified {{Code|$id}}. The output format is identical to [[#sql:execute|sql:execute]]. The optional parameter {{Code|$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/ >
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
 
element sql:parameters {
 
element sql:parameters {
 
   element sql:parameter {
 
   element sql:parameter {
Line 85: Line 79:
 
   }+
 
   }+
 
}?
 
}?
</pre>
+
</syntaxhighlight>
 
With {{Code|$options}}, the following parameter can be set:
 
With {{Code|$options}}, the following parameter can be set:
 
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 
* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.
 
|-
 
|-
 
| '''Errors'''
 
| '''Errors'''
|{{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}} wrong number of {{Code|<sql:parameter/>}} elements, or parameter type is not 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.
+
|{{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.
 
|}
 
|}
  
Line 155: Line 149:
 
A simple select statement can be executed as follows:
 
A simple select statement can be executed as follows:
  
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
 
let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 
let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")
 
return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")
 
return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")
</pre>
+
</syntaxhighlight>
  
 
The result may look like:
 
The result may look like:
  
<pre class="brush:xml">
+
<syntaxhighlight lang="xml">
 
<sql:row xmlns:sql="http://basex.org/modules/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>
Line 177: Line 171:
 
   <sql:column name="total">14</sql:column>
 
   <sql:column name="total">14</sql:column>
 
</sql:row>
 
</sql:row>
</pre>
+
</syntaxhighlight>
  
 
==Prepared Statements==
 
==Prepared Statements==
Line 183: Line 177:
 
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 195: Line 189:
 
(: Execute prepared statement :)
 
(: Execute prepared statement :)
 
return sql:execute-prepared($prep, $params)
 
return sql:execute-prepared($prep, $params)
</pre>
+
</syntaxhighlight>
  
 
==SQLite==
 
==SQLite==
  
The following expression demonstrates how SQLite can be addressed using the [http://bitbucket.org/xerial/sqlite-jdbc Xerial SQLite JDBC driver]:
+
The following expression demonstrates how SQLite can be addressed with the [https://bitbucket.org/xerial/sqlite-jdbc/ Xerial SQLite JDBC driver]:
  
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
 
(: Initialize driver :)
 
(: Initialize driver :)
 
sql:init("org.sqlite.JDBC"),
 
sql:init("org.sqlite.JDBC"),
Line 217: Line 211:
 
   sql:execute($conn, "select * from person")
 
   sql:execute($conn, "select * from person")
 
)
 
)
</pre>
+
</syntaxhighlight>
  
 
=Errors=
 
=Errors=
 
{{Mark|Updated with Version 9.0:}}
 
  
 
{| class="wikitable" width="100%"
 
{| class="wikitable" width="100%"
Line 240: Line 232:
 
|-
 
|-
 
|{{Code|parameters}}
 
|{{Code|parameters}}
|Wrong number of {{Code|&lt;sql:parameter/&gt;}} elements, or parameter type is not specified.
+
|No parameter type specified.
 
|-
 
|-
 
|{{Code|timeout}}
 
|{{Code|timeout}}

Revision as of 12:31, 2 July 2020

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

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

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 init: the specified driver is not found.

sql:connect

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:

<syntaxhighlight lang="xquery"> sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() }) </syntaxhighlight>

sql:execute

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

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:

<syntaxhighlight lang="xquery"> element sql:parameters {

 element sql:parameter {
   attribute type { "int" | "string" | "boolean" | "date" | "double" |
     "float" | "short" | "time" | "timestamp" | "sqlxml" },
   attribute null { "true" | "false" }?,
   text
 }+

}? </syntaxhighlight> 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

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

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

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

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

Direct queries

A simple select statement can be executed as follows:

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

The result may look like:

<syntaxhighlight lang="xml"> <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">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://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> </syntaxhighlight>

Prepared Statements

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

<syntaxhighlight lang="xquery"> (: 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) </syntaxhighlight>

SQLite

The following expression demonstrates how SQLite can be addressed with the 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

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

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.