I am using Postgis 2.4 with posgresql 10 in Windows 10. I have the following SQL query:

WITH data (the_geom) as (   SELECT a.gid,           CASE WHEN ST_Within(a.geom,b.geom) THEN a.geom                 ELSE ST_Intersection(a.geom,b.geom)            END AS the_geom     FROM source.g100_wby_lakes_r as a        JOIN extents.map_areas as b ON ST_Intersects(a.geom,b.geom)    WHERE b.map_id='AA01' )  INSERT into public.g100_wby_lakes_r (gid,geom)  select *  from data  where st_GeometryType(the_geom)='MULTIPOLYGON'; 

It tries to select the intersection between two multipolygons and only insert into a new table the intersected geometries which are also multipolygons (the intersection could also result in points or lines). All works except for the WHERE clause which gives the following error:

ERROR:  column reference "the_geom" is ambiguous LINE 4: ...id,geom) select * from data where st_GeometryType(the_geom)=...                                                              ^ SQL state: 42702 Character: 351 

Why is the_geom ambiguous? How can I change the SQL to make it work? Thank you