如何将 SQLite 表转换为 SpatiaLite 表？

Question

我在 SQLite 数据库中有一个 Pandas 表，其中有 40 个奇数列，所有这些列都可能需要在 QGIS 中进行查询。该表包含 XY 数据和以前的 Python 代码捕获创建点所需的 EPSG 代码。如何将我的 Pandas 或 SQLite 表转换为 SpatiaLite 表？

spatialite_path = 'C:\Program Files (x86)\Spatialite'
os.environ['PATH'] = spatialite_path + ';' + os.environ['PATH']

con.enable_load_extension(True)
con.load_extension("mod_spatialite")
con.execute("SELECT InitSpatialMetaData();")

Tables = table_clean_wGIS,pandas_table_wXY,db_table_wXY
Variables = db_name (string), EPSG_Code (int)

最初，根据the old SpatiaLite Cookbook，我使用AddGeometryColumn 创建了一个带有主键和X 和Y 的表：

con = sqlite3.connect(db_name)
cur = con.cursor()
cur.execute('CREATE TABLE IF NOT EXISTS table_clean_wGIS (ID REAL PRIMARY KEY, UniquePointName TEXT DEFAULT 0, X DOUBLE DEFAULT 0, Y DOUBLE DEFAULT 0, Date TEXT )')

cur.execute('SELECT AddGeometryColumn("table_clean_wGIS", "geometry",(?),"POINT",0)', (EPSG_Code,))
cur.execute('SELECT CreateSpatialIndex("table_clean_wGIS","geometry")')
cur.execute('INSERT INTO table_clean_wGIS(ID, UniquePointName,X,Y, Date, geometry) SELECT ID, UniquePointName, X,Y,Date,MakePoint(X,Y,?) FROM pandas_table_wXY', (EPSG_Code,))
con.commit()
con.close()

这有效，但只有几列。我尝试了FULL OUTER JOIN（SQLite 不支持它），然后是双倍的LEFT JOIN，但我认为它忘记了它是几何图形。然后我用Insert Into 将AddGeometryColumn 设置为最初的40+ 列表，但这创建了双倍的行正确的几何形状但不是与行有关。

con = sqlite3.connect(db_name)
cur = con.cursor()        

cur.execute('SELECT AddGeometryColumn ("db_table_wXY", "geometry",(?),"POINT",0)', (EPSG_Code,))

cur.execute('SELECT CreateSpatialIndex("db_table_wXY","geometry")')

cur.execute('INSERT INTO db_table_wXY(geometry) SELECT MakePoint(X,Y,?) FROM db_table_wXY', (EPSG_Code,))
con.commit()
con.close()

我尝试了 Update-Set，似乎这有效，但结果没有显示在 QGIS 中。

cur.execute('SELECT AddGeometryColumn ("db_pss", "geometry",(?),"POINT",0)', (EPSG_Code,))

cur.execute('UPDATE db_pss SET geometry =MakePoint(X,Y,?)', (EPSG_Code,))

cur.execute('SELECT CreateSpatialIndex("db_pss","geometry")')
con.commit()
con.close()

Answer 1

最后我猜想'n'在代码末尾检查了我使用这个花絮的方式：

cur.execute('SELECT RecoverGeometryColumn("table_with_XY", "geometry", (?), "POINT", "XY")', (EPSG_Code,))

完整代码：

#This only has to happen once per computer (i think) so feel free to skip these 2 lines
spatialite_path = 'C:Program Files (x86)Spatialite'
os.environ['PATH'] = spatialite_path + ';' + os.environ['PATH']

#Variables: db_name, EPSG_Code
#Connect to the database
con = sqlite3.connect(db_name)
cur = con.cursor()  
#Initialise Spatialite - this has to be done to create geometry binaries
con.enable_load_extension(True)
con.load_extension("mod_spatialite")
con.execute("SELECT InitSpatialMetaData();")      

#Add a blank/empty geometry column (I'm using Point data)
#the ? is to add a variable into a python based sql statement. EPSG_Code
cur.execute('SELECT AddGeometryColumn ("table_with_XY", "geometry",(?),"POINT",0)', (EPSG_Code,))

#This is where we make our points from the X and Y column in the table
cur.execute('UPDATE table_with_XY SET geometry =MakePoint(X,Y,?)', (EPSG_Code,))

#This line I have to use even though I don't think it should be necessary but it makes my code work so...
cur.execute('SELECT RecoverGeometryColumn("table_with_XY", "geometry", (?), "POINT", "XY")', (EPSG_Code,))
#Spatial Index to improve performance 
cur.execute('SELECT CreateSpatialIndex("table_with_XY","geometry")')
#commit the changes and always close your connection to the database
con.commit()
con.close()

这似乎是您可以从同一个表中的 X 和 Y 数据轻松创建几何图形的方式。我不确定它是最佳的。 事后看来，这可能与主键有关。