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Artifact ID:	64df71ad6734f958727608ce4e1f6c3dd10bb7d4
Page Name:	ZippedSHP
Date:	2020-05-08 09:16:14
Original User:	sandro
Parent:	d1f953cf63330714941fe06556b55e00996f8cd1 (diff)
Next	a2a1995d003686095779367b8112c58f1ea06037

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Reading SHP and DBF files directly from within a Zipfile

Starting since version 5.0.0 SpatiaLite has the capability to directly read any Shapefile (or DBF file) contained within a compressed Zipfile.
Several closely related SQL functions have been introduced as well.

Accessing a Zipped SHP

All these new SQL functions are now supported:

• ImportZipSHP(): the main function allowing to import a whole Shapefile into a new Spatial Table into the currently connected Database.
• PROJ_GuessSridFromZipSHP(): a helper fuction for attempting to guess the SRID for a given zipped SHP.
• Zipfile_NumSHP(): a helper function returning the total count of Shapefiles contained within a given Zipfile.
• Zipfile_ShpN(): a helper function returning the basename for the Nth Shapefile contained within a given Zipfile.

We'll now start a quick tutorial about using all these new SQL functions. Note: the tutorial is based on the dataset you can download from here

SELECT Zipfile_NumSHP ( 'c:/users/afuri/Downloads/Limiti01012020.zip' )
------------
4

• the SQL function Zipfile_NumSHP() will inspect a Zipfile then returning the total count of Shapefiles it contains.
• it requires just a single argument: the absolute or relative path leading to the Zipfile.
• Note it will return 0 if the Zipfile does not contain any Shapefile.
  • NULL will be returned if the Zipfile does not exist of if it's corrupted or invalid.

SELECT Zipfile_shpN ( 'c:/users/afuri/Downloads/Limiti01012020.zip' , 1 )
------
Limiti01012020/Com01012020/Com01012020_WGS84

SELECT Zipfile_shpN ( 'c:/users/afuri/Downloads/Limiti01012020.zip' , 2 )
------
Limiti01012020/ProvCM01012020/ProvCM01012020_WGS84

SELECT Zipfile_shpN ( 'c:/users/afuri/Downloads/Limiti01012020.zip' , 3 )
------
Limiti01012020/Reg01012020/Reg01012020_WGS84

SELECT Zipfile_shpN ( 'c:/users/afuri/Downloads/Limiti01012020.zip' , 4 )
-------
Limiti01012020/RipGeo01012020/RipGeo01012020_WGS84

• the SQL function Zipfile_ShpN() will inspect a Zipfile then returning the basename of the Nth Shapefile it contains.
• it requires two argumenst:
  • the absolute or relative path leading to the Zipfile.
  • the relative index (1 based) of the Shapefile within the Zipfile.
• Note: NULL will be returned if the Zipfile does not exist of if it's invalid or if the index value is outside the expected range.

SELECT PROJ_GuessSridFromZipSHP ( 'c:/users/afuri/Downloads/Limiti01012020.zip' , 'Limiti01012020/Com01012020/Com01012020_WGS84' )
------------
32632

• the SQL function PROJ_GuessSridFromZipSHP() will inspect a Zipfile then returning the SRID value declared by the .PRJ member of the Shapefile contained into the Zipfiles as identified by its basename.
• it requires two argumenst:
  • the absolute or relative path leading to the Zipfile.
  • the basename of the Shapefile within the Zipfile (without adding any .shp, .shx or .dbf suffix).
• Note: -1 will be returned if the Shapefile has no .PRJ member, of if it contains an invalid WKT definition.
NULL will be returned on invalid arguments or if the Shapefile does not exist.

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Accessing a Zipped DBF

All these new SQL functions are now supported:

• ImportZipDBF(): the main function allowing to import a whole DBF file into a new Table into the currently connected Database.
• Zipfile_NumDBF(): a helper function returning the total count of DBF files contained within a given Zipfile.
• Zipfile_DbfN(): a helper function returning the filename for the Nth DBF file contained within a given Zipfile.

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