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199 bytes added ,  18:51, 18 November 2020
This [[Module Library|XQuery Module]] contains a single function to parse CSV input. [http CSV] (comma-separated values) is a popular representation for tabular data, exported e. g. from Excel.
{{Mark|Updated with Version 9.0:}}
All functions and errors in this module are assigned to the <code><nowiki></nowiki></code> namespace, which is statically bound to the {{Code|csv}} prefix.<br/>
If the {{Code|direct}} or {{Code|attributes}} format is chosen, a CSV string is converted to XML:
* The resulting XML document has a {{Code|<csv>}} root element.* Rows are represented via {{Code|<record>}} elements.* Fields are represented via {{Code|<entry>}} elements. The value of a field is represented as text node.* If the {{Code|header}} option is set to {{Code|true}}, the first text line is parsed as table header, and the {{Code|<entry>}} elements are replaced with the field names:** Empty names are represented by a single underscore ({{Code|_}}), and characters that are not valid in element names are replaced with underscores or (when invalid as first character of an element name) prefixed with an underscore.** If the {{Code|laxformat}} option is set to {{Code|falsedirect}}, invalid characters will be rewritten to an underscore and the character’s four-digit Unicodefield names are encoded, as described in the [[Conversion Module#Keys|Conversion Module]], and underscores will be represented used as two underscores ({{Code|__}}). The resulting element names may be less readable, but can always be converted back to the original field names.* If * Otherwise, if {{Code|format}} is set to {{Code|attributes}}, the field names will be stored in name attributes.
'''A little advice''': in the Database Creation dialog of the GUI, if you select CSV Parsing and switch to the ''Parsing'' tab, you can see the effects of some of the conversion options.
This format has been introduced with {{Version|9.0}}. It is more flexible and light-weight than the old, discarded {{Code|map}} format.
With the {{Code|xquery}} format, CSV records are converted to a sequence of arrays:
* <code>$csv?names?*</code> returns the names of all fields (if available)
* Return enumerated strings for all records:
<pre classsyntaxhighlight lang="brush:xquery">
for $record at $pos in $csv?records
return $pos || ". " || string-join($record?*, ', ')
The resulting representation consumes less memory than XML-based formats, and values can be directly accessed without conversion. Thus, it is recommendable for very large inputs and for efficient ad-hoc processing.
* With {{Code|attributes}} conversion, field names are stored in {{Code|name}} attributes
* With {{Code|xquery}} conversion, the input is converted to an XQuery map
| {{Code|direct}}, {{Code|attributes}}, {{Code|mapxquery}}
| {{Code|direct}}
| Specifies how quotes are parsed:
* Parsing: If the option is enabled, quotes at the start and end of a value will be treated as control characters. Separators and newlines within the quotes will be adopted without change.
* Serialization: If the option is enabled, the value will be wrapped with quotesif it contains characters that might be treated as control characters. A quote character in the value will be encoded according to the rules of the {{Code|backslashes}} option.
| {{Code|yes}}, {{Code|no}}
| {{Code|yes}}
| width='120' | '''Signatures'''
|{{Func|csv:parse|$input string as xs:string?|document-nodeitem(element(csv))?}}<br/>{{Func|csv:parse|$input string as xs:string?, $options as map(*)?|item()?}}
| '''Summary'''
|Converts the CSV data specified by {{Code|$inputstring}} to an XML document or a mapXQuery value. The {{Code|$options}} argument can be used to control the way the input is converted.
| '''Errors'''
|{{Error|parse|#Errors}} the specified input cannot be parsedas CSV document.|} ==csv:doc== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|csv:doc|$uri as xs:string?|item()?}}<br />{{Func|csv:doc|$uri as xs:string?, $options as map(*)?|item()?}}<br />|-| '''Summary'''|Fetches the CSV document referred to by the given {{Code|$uri}} and converts it to an XQuery value. The {{Code|$options}} argument can be used to control the way the input is converted.|-| '''Errors'''|{{Error|parse|#Errors}} the specified input cannot be parsed as CSV document.<br/>{{Error|options|#Errors}} the specified options are conflicting.
'''Input''' {{Code|addressbook.csv}}:
<pre classsyntaxhighlight lang="brush:xml">
Name,First Name,Address,City
Huber,Sepp,Hauptstraße 13,93547 Hintertupfing
<pre classsyntaxhighlight lang="brush:xquery">
let $text := file:read-text('addressbook.csv')
return csv:parse($text, map { 'header': true() })
<pre classsyntaxhighlight lang="brush:xml">
<pre classsyntaxhighlight lang="brush:xquery">
let $options := map { 'lax': false() }
let $input := file:read-text('some-data.csv')
let $output := $input => csv:parse($options) => csv:serialize($options)
return $input eq $output
'''Example 3:''' Converts CSV data to XQuery and returns distinct column values:
<pre classsyntaxhighlight lang="brush:xquery">
let $text := ``[Name,City
let $records := $csv('records')
for $name at $pos in $csv('names')?*
let $values := $records?($pos)
return (
'* ' || $name || ': ' || string-join(distinct-values($values), ', ')
<pre classsyntaxhighlight lang="brush:xquery">
Distinct values:
* Name: Jack, John
* City: Chicago, Washington, New York
{{Mark|Updated with Version 9.0:}}
{| class="wikitable" width="100%"
;Version 9.4
* Added: [[#csv:doc|csv:doc]]
; Version 9.1
* Updated: [[#csv:parse|csv:parse]] can be called with empty sequence.
;Version 9.0
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