SQL查询：针对每个州的特定水手人数

Question

I'm starting to learn to write SQL queries. However, I'm still struggling with that. I had to write a query that gives back for each state that has more than 5 sailors the sailor id and the total number of reservations that he has made. The schemas are as following:

Slr ( sid , sname , rating , state ) and Reserves ( sid , bid , day ).

Here's my trial:

Select slr.state, slr.sid, count(*)
From slr left join Reserves on slr.sid=reserves.sid
Group By s.state
Having count(*) >= 5

I know it's not correct, but what can I change ?

Answer 1

Something like this should get you started.

select slr.id
, state
, count(*) records

from slr join
(select state thestate, count(*) staterecords
 from slr
 group by state
 having count(*) >= 5 ) temp on state = thestate
 group by slr.id

This gives you the sailor id's in states with 5 or more sailors. There is nothing in your question that helps me with the part about how many reservations he has made.