我的sqlite3游标的行数少于预期

Question

在下面的代码中，我有两个游标，第一个loc_crs应该有3行。但是当我运行我的程序时，loc_crs似乎只有1行

import db_access

def get_average_measurements_for_area(area_id):
"""
Returns the average value of all measurements for all locations in the given area.
Returns None if there are no measurements.
"""
loc_crs = db_access.get_locations_for_area(area_id)

avg = 0
for loc_row in loc_crs:

    loc_id = int(loc_row['location_id'])
    meas_crs = db_access.get_measurements_for_location(loc_id)

    for meas_row in meas_crs:
        meas = float(meas_row['value'])
        avg += meas
        # print("meas: ", str(meas))

    print("loc_id: ", str(loc_id))
print(str(avg))

get_average_measurements_for_area（3）

这是我的输出。

loc_id:  16
avg:  568.2259127787871

编辑：以下是被调用的方法：

def get_locations_for_area(area_id):
"""
Return a list of dictionaries giving the locations for the given area.
"""
cmd = 'select * from location where location_area is ?'
crs.execute(cmd, [area_id])

return crs

def get_measurements_for_location(location_id):
"""
Return a list of dictionaries giving the measurement rows for the given location.
"""
cmd = 'select value from measurement where measurement_location is ?'
crs.execute(cmd, [location_id])
return crs

以下是数据库的链接： http://cs.kennesaw.edu/~bsetzer/4320su15/extra/databases/measurements/measures.sqlite