The jdbc_query element is used to define a theme dynamically. This element and its associated <hidden_info> element have the following definitions:

<!ELEMENT jdbc_query (#PCDATA, hidden_info?)>
<!ATTLIST jdbc_query
  asis (TRUE|FALSE) "FALSE"
  spatial_column CDATA #REQUIRED
  key_column CDATA #IMPLIED
  label_column CDATA #IMPLIED
  label_style CDATA #IMPLIED
  render_style CDATA #IMPLIED
  x_column CDATA #IMPLIED
  y_column CDATA #IMPLIED
  datasource CDATA #IMPLIED
  jdbc_host CDATA #IMPLIED
  jdbc_port CDATA #IMPLIED
  jdbc_sid CDATA #IMPLIED
  jdbc_user CDATA #IMPLIED
  jdbc_password CDATA #IMPLIED
  jdbc_srid CDATA #IMPLIED
  jdbc_mode (thin|oci8) "thin"
>
<!ELEMENT hidden_info (field+)>
<!ELEMENT field (#PCDATA)>
<!ATTLIST field
  column CDATA #REQUIRED
  name CDATA #IMPLIED
>

To define a theme dynamically, you must supply a valid SQL query as the content of the <jdbc_query> element. You must specify the spatial_column (column of type SDO_GEOMETRY) and the JDBC connection information for a dynamically defined theme (either datasource or the combination of jdbc_host, jdbc_port, jdbc_sid, jdbc_user, and jdbc_password). If the selectable_in_svg attribute value is TRUE in the <theme> element, you must use the key_column attribute in the <jdbc_query> element to specify the name of a column that can uniquely identify each selected feature from the JDBC query. The specified column must also appear in the SELECT list in the JDBC query.

render_style and label_style are optional attributes. For render_style, for point features the default is a red cross rotated 45 degrees, for lines and curves it is a black line 1 pixel wide, and for polygons it is a black border with a semitransparent dark gray interior.

x_column and y_column are optional attributes. If specified, they are used to define a point JDBC theme based on two columns in a table, so that MapViewer can render a point theme based on values in these columns. For more information, see Defining a Point JDBC Theme Based on Two Columns.

jdbc_srid is an optional attribute that specifies the coordinate system (SDO_SRID value) of the data to be rendered.

jdbc_mode identifies the Oracle JDBC driver (thin or oci8) to use to connect to the database.

asis is an optional attribute. If it is set to TRUE, MapViewer does not attempt to modify the supplied query string. If asis is FALSE (the default), MapViewer embeds the SQL query as a subquery of its spatial filter query. For example, assume that you want a map centered at (-122, 37) with size 1, and the supplied query is: SELECT geometry, sales FROM crm_sales WHERE sales < 100000;

If asis is FALSE, the actual query that MapViewer executes is similar to:

SELECT * FROM
(SELECT geometry, sales FROM crm_sales WHERE sales < 100000)
WHERE sdo_filter(geometry, sdo_geometry(. . . -122.5, 36.5, -123.5, 37.5. . . ) ='TRUE';

In other words, the original query is further refined by a spatial filter query using the current map window. However, if asis is TRUE, MapViewer executes the query as specified, namely: SELECT geometry, sales FROM crm_sales WHERE sales < 100000;

The <hidden_info> element specifies the list of attributes from the base table to be displayed when the user moves the mouse over the theme's features. The attributes are specified by a list of <field> elements. Each <field> element must have a column attribute, which specifies the name of the column from the base table, and it can have a name attribute, which specifies the display name of the column. (The name attribute is useful if you want a text string other than the column name to be displayed.)

For examples of using the <jdbc_query> element to define a theme dynamically, see Example 3-2 and Example 3-4.