我有一个sqlite数据库，我可以读为：
In [42]: df = pd.read_sql("SELECT * FROM all_vs_all", engine)
In [43]:
In [43]: df.head()
Out[43]:
user_data user_model \
0 037d05edbbf8ebaf0eca@172.16.199.165 037d05edbbf8ebaf0eca@172.16.199.165
1 037d05edbbf8ebaf0eca@172.16.199.165 060210bf327a3e3b4621@172.16.199.33
2 037d05edbbf8ebaf0eca@172.16.199.165 1141259bd36ba65bef02@172.21.44.180
3 037d05edbbf8ebaf0eca@172.16.199.165 209627747e2af1f6389e@172.16.199.181
4 037d05edbbf8ebaf0eca@172.16.199.165 303a1aff4ab6e3be82ab@172.21.112.182
score Class time_secs model_name bin_id
0 0.283141 0 1514764800 Flow 0
1 0.999300 1 1514764800 Flow 0
2 1.000000 1 1514764800 Flow 0
3 0.206360 1 1514764800 Flow 0
4 1.000000 1 1514764800 Flow 0
由于表太大，我没有阅读完整的表，而是选择了行的随机子集：
这可以很方便地完成，因为：
random_query = "SELECT * FROM all_vs_all WHERE abs(CAST(random() AS REAL))/9223372036854775808 < %f AND %s" % (ratio, time_condition)
df = pd.read_sql(random_query, engine)
问题在于，对于每个三元组[user_data, user_model, time_secs]，我想获取包含该三元组的所有行。每个三元组出现1或2次。
执行此操作的一种可能方法是，首先对一组三元组进行随机采样，然后获取具有所选三元组之一的所有行，但这似乎太慢了。
有没有一种有效的方法？
编辑：如果我可以将所有数据加载到熊猫中，我会做类似的事情：
selected_groups = []
for group in df.groupby(['user_data', 'user_model', 'time_secs']):
if np.random.uniform(0,1) > ratio:
selected_groups.append(group)
res = pd.concat(selected_groups)
答案 0 :(得分：0)
很少有示例联接和sql查询：
当前被承认：
Select p.patient_no, p.pat_name,p.date_admitted,r.room_extension,p.date_discharged FROM Patient p JOIN room r ON p.room_location = r.room_location where p.date_discharged IS NULL ORDER BY p.patient_no,p.pat_name,p.date_admitted,r.room_extension,p.date_discharged;
空房间：
SELECT r.room_location, r.room_accomadation, r.room_extension FROM room r where r.room_location NOT IN (Select p.room_location FROM patient.p where p.date_discharged IS NULL) ORDER BY r.room_location, r.room_accomadation, r.room_extension;
尚无收费：
SELECT p.patient_no, p.pat_name, COALESCE (b.charge,0.00) charge FROM patient p LEFT JOIN billed b on p.patient_no = b.patient_no WHERE p.patient_no NOT IN (SELECT patient_no FROM billed) group by p.patient_no ORDER BY p.patient_no, p.pat_name,charge;
最高薪水：
SELECT phy_id,phy_name, salary FROM physician where salary in (SELECT MAX(salary) FROM physician) UNION
SELECT phy_id,phy_name, salary FROM physician where salary in (SELECT MIN(salary) FROM physician) ORDER BY phy_id,phy_name, salary;
消耗的各种物品
select p.pat_name, i.discription, count (i.item code) as item code from patient p join billed b on p.patient no = b. patient no join item i on b.item code = i.item code group by p.patient no, i.item code order by..
未接受治疗的患者
SELECT p.patient_no,p.pat_name FROM patient p where p.patient_no NOT IN (SELECT t.patient_no FROM treats t)
ORDER BY p.patient_no,p.pat_name;
2高薪：
Select phy_id, phy_name, date_of_joining, max(salary) as salary from physician group by salary having salary IN (Select salary from physician)
Order by phy_id, phy_name, date_of_joining, salary limit 2;
超过200：
select patient_no, sum (charge), as total charge from billed group by patient no having total charges > 200 order by patient no, total charges