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
All functions in this module are assigned to the http://basex.org/modules/sql
namespace, which is statically bound to the sql
prefix.
All errors are assigned to the http://basex.org/errors
namespace, which is statically bound to the bxerr
prefix.
Functions
sql:init
Signatures | sql:init($class as xs:string) as empty-sequence()
|
Summary | This function initializes a JDBC driver specified via $class . This step might be superfluous if the SQL database is not embedded. |
Errors | BXSQ0007 : the specified driver class is not found.
|
sql:connect
Signatures | sql:connect($url as xs:string) as xs:integer sql:connect($url as xs:string, $user as xs:string, $password as xs:string) as xs:integer sql:connect($url as xs:string, $user as xs:string, $password as xs:string, $options as item()) as xs:integer |
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 $options parameter can be used to set connection options, which can either be specified
<sql:options> <sql:autocommit value='true'/> ... </sql:options>
map { "autocommit": true(), ... } |
Errors | BXSQ0001 : an SQL exception occurs, e.g. missing JDBC driver or not existing relation.
|
sql:execute
Once a connection is established, the returned connection handle can be used to execute queries on the database. Our SQL module supports both direct queries and prepared statements.
Signatures | sql:execute($connection as xs:integer, $query as xs:string) as element()*
|
Summary | This function executes a query or update statement. The parameter $connection specifies a connection handle. The parameter $query is a string representing an SQL statement.
|
Errors | BXSQ0001 : an SQL exception occurs, e.g. not existing relation is retrieved.
|
sql:execute-prepared
Signatures | sql:execute-prepared($id as xs:integer, $params as element(sql:parameters)) as element()*
|
Summary | This function executes a prepared statement. The parameter $id specifies a prepared statement handle. The optional parameter $params is an element <sql:parameters/> representing the parameters for a prepared statement along with their types and values. The following schema shall be used:element sql:parameters { element sql:parameter { attribute type { "int"|"string"|"boolean"|"date"|"double"|"float"|"short"|"time"|"timestamp" }, attribute null { "true"|"false" }?, text }+ }? |
Errors | BXSQ0001 : an SQL exception occurs, e.g. not existing relation is retrieved.
|
sql:prepare
Signatures | sql:prepare($connection as xs:integer, $statement as xs:string) as xs:integer
|
Summary | This function prepares a statement and returns a handle to it. The parameter $connection indicates the connection handle to be used. The parameter $statement is a string representing an SQL statement with one or more '?' placeholders. If the value of a field has to be set to NULL , then the attribute null of the element <sql:parameter/> has to be true .
|
Errors | BXSQ0001 : an SQL exception occurs.
|
sql:commit
Signatures | sql:commit($connection as xs:integer) as empty-sequence()
|
Summary | This function commits the changes made to a relational database. $connection specifies the connection handle.
|
Errors | BXSQ0001 : an SQL exception occurs.
|
sql:rollback
Signatures | sql:rollback($connection as xs:integer) as empty-sequence()
|
Summary | This function rolls back the changes made to a relational database. $connection specifies the connection handle.
|
Errors | BXSQ0001 : an SQL exception occurs.
|
sql:close
Signatures | sql:close($connection as xs:integer) as empty-sequence()
|
Summary | This function closes a connection to a relational database. $connection specifies the connection handle.
|
Errors | BXSQ0001 : an SQL exception occurs.
|
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://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> <sql:row xmlns:sql="http://basex.org/modules/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">2014-10-10 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 $params := <sql:parameters> <sql:parameter type='double'>10</sql:parameter> <sql:parameter type='string'>French_Roast</sql:parameter> </sql:parameters> (: Execute prepared statement :) return sql:execute-prepared($prep, $params)
SQLite
The following expression demonstrates how SQLite can be addressed using 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"), sql:close($conn) )
Errors
Code | Description |
---|---|
BXSQ0001
|
An SQL exception occurred (e.g.: a non-existing relation is retrieved). |
BXSQ0002
|
A wrong connection handle or prepared statement handle is passed. |
BXSQ0003
|
The number of <sql:parameter/> elements in <sql:parameters/> differs from the number of placeholders in the prepared statement.
|
BXSQ0004
|
The type of a parameter for a prepared statement is not specified. |
BXSQ0005
|
An attribute different from type and null is set for a <sql:parameter/> element.
|
BXSQ0006
|
A parameter is from type date, time or timestamp and its value is in an invalid format. |
BXSQ0007
|
A specified database driver class is not found. |
Changelog
- Version 7.5
- Updated: prepared statements are now executed via sql:execute-prepared
The module was introduced with Version 7.0.