[postgis-users] Create View From Spatial Table with libpq

[郭家成]

Hi !
I try to create a view from a spatial table, but it can't be done
successfully, please give me some hints.

Here is how I create my spatial table:

*CREATE TABLE "table_name" ("ID" SERIAL PRIMARY KEY);
SELECT ADDGEOMETRYCOLUMN('', 'table_name', 'geocol', -1, 'MULTIPOLYGON', 2);
*

After I inserted 1000 records into this table, I try to create a view with
libpq:

*int wkblen=0;*
*char *pwkb = MakeWKB(&wkblen);* // I wrote a function to make wkb
format, the function works fine.
*Oid paramtypes[1]={0};*
*char* paramvalues[1]={pwkb};*
*int paramlens[1]={wkblen};
int paramformats[1]={1};*
*int resultformat=1;*

*PGresult *r = PQexecParams(conn,*
*              "CREATE VIEW \"view_name\" AS SELECT * FROM \"table_name\"
WHERE ST_Intersects(\"geocol\", $1)",*
*              1,*
*              paramtypes,*
*              paramvalues,*
*              paramlens,*
*              paramformats,*
*              resultformat);*
*ExecStatusType est = PQresultstatus(r);*

The ExecStatusType is always be *PGRES_FATAL_ERROR*, and Error Message
is *"could
not determine data type of parameter $1"*.
I have no idea what's going on, because when I change the SQL syntax to:

*"SELECT * FROM \"table_name\" WHERE ST_Intersects(\"geocol\", $1)"*

The ExecStatusType will be PGRES_TUPLES_OK.

Please give me some hints, Thanks !
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