Question

I’m working on my homework and am having trouble figuring out the correct syntax for the “NOT IN” functionality.

The database is a small insurance database (carriers, members, employers, plans) made up for this assignment. I am supposed to “List ALL carriers and the count of plans they have. (use either the right or left join). List the carrier_id, carname, and the count of plans.”

This is what I have written as of right now:

SELECT carrier_id, carname, count(*) AS NoPlans
FROM carriers RIGHT JOIN plans
ON carriers.carrier_id = plans.carrierid;

This throws the “not a single-group group function” error when I try to run it, but that’s because I think it’s looking for a WHERE clause, and I don’t know what the condition should be.

Carrier table structure:

Name                           Null     Type
------------------------------ -------- -----------
CARRIER_ID                     NOT NULL CHAR(4)
CARNAME                                 CHAR(35)
CARADDRESS                              CHAR(50)
CARCITY                                 CHAR(30)
CARSTCODE                               CHAR(2)
CARZIP                                  CHAR(10)
CARPHONE                                CHAR(10)
CARWEBSITE                              CHAR(255)
CARCONTACTFIRSTNAME                     CHAR(35)
CARCONTACTLASTNAME                      CHAR(35)
CARCONTACTEMAIL                         CHAR(255)

11 rows selected

Plans table structure:

Name                           Null     Type
------------------------------ -------- -------------
PLANID                         NOT NULL NUMBER
PLNDESCRIPTION                          CHAR(35)
PLNCOST                                 NUMBER(8,2)
CARRIERID                               CHAR(4)

4 rows selected

Answer 1

SELECT carrier_id, carname, count(*) AS NoPlans 
  FROM carriers RIGHT JOIN plans 
    ON carriers.carrier_id = plans.carrierid
 GROUP BY carrier_id, carname;