The SE_AsShape() function

The SE_AsShape() function takes a geometry object and returns it in ESRI shapefile format.

The return type of SE_AsShape() is defined as ST_Geometry to allow spatial objects greater than 2 kilobytes in size to be retrieved by a client application.

Typically, you use ST_AsShape() to retrieve spatial data from the server and send it to a client, as in:

SELECT SE_AsShape(geomcol) FROM mytable

HCL OneDB™ automatically casts the output of the SE_AsShape() function to the proper data type for transmission to the client.

You can write user-defined routines (UDRs) in C or SPL to extend the functionality of the existing spatial data type functions. You can use SE_AsShape() to convert an ST_Geometry to ESRI shapefile format. If you pass the output of SE_AsShape() to another UDR whose function signature requires an LVARCHAR input, you should explicitly cast the return type of SE_AsShape() to LVARCHAR, as in:

EXECUTE FUNCTION MySpatialFunc(SE_AsShape(geomcol)::lvarchar);

Syntax

SE_AsShape(g1 ST_Geometry)

Return type

ST_Geometry

Example

The code fragment below illustrates how the SE_AsShape() function converts the zone polygons of the sensitive_areas table into shape polygons. These shape polygons are passed to the application's draw_polygon() function for display:

/* Create the SQL expression. */
    sprintf(sql_stmt,
            "SELECT SE_AsShape(zone) "
            "FROM sensitive_areas WHERE "
            "SE_EnvelopesIntersect(zone,SE_PolyFromShape(?,%d))", srid);

    /* Prepare the SQL statement. */
    SQLPrepare(hstmt, (UCHAR *)sql_stmt, SQL_NTS);

    /* Bind the query geometry parameter. */
    pcbvalue1 = query_shape_len;
    SQLBindParameter (hstmt, 1, SQL_PARAM_INPUT, SQL_C_BINARY,
                      SQL_INFX_UDT_LVARCHAR, query_shape_len, 0,
                      query_shape_buf, query_shape_len, &pcbvalue1);

    /* Execute the query. */
    rc = SQLExecute(hstmt);

    /* Assign the results of the query (the Zone polygons) to the
       fetched_shape_buf variable. */
    SQLBindCol (hstmt, 1, SQL_C_BINARY,
                fetched_shape_buf, 10000, &fetched_shape_len);

    /* Fetch each polygon within the display window and display it. */
    while (SQL_SUCCESS == (rc = SQLFetch(hstmt)))
        draw_polygon(fetched_shape_buf);