我正在使用 postgresql 并且我有一个名为 accidents(状态，总事故)的表和另一个名为 population 的表。我想获得事故总数最高的前 3 个州名，然后在 postgresql 中得到这 3 个州的人口除以事故总数？下面的查询语句怎么写？
解释:
人口表
rank| state | population
---+-----------------------------+------------
1 | Uttar Pradesh | 199581477
2 | Maharashtra | 112372972
3 | Bihar | 103804630
4 | West Bengal | 91347736
5 | Madhya Pradesh | 72597565
6 | Tamil Nadu | 72138958
7 | Rajasthan | 68621012
8 | Karnataka | 61130704
9 | Gujarat | 60383628
10 | Andhra Pradesh | 49665533
11 | Odisha | 41947358
12 | Telangana | 35193978
13 | Kerala | 33387677
14 | Jharkhand | 32966238
15 | Assam | 31169272
16 | Punjab | 27704236
17 | Haryana | 25753081
18 | Chhattisgarh | 25540196
19 | Jammu and Kashmir | 12548926
20 | Uttarakhand | 10116752
21 | Himachal Pradesh | 6856509
22 | Tripura | 3671032
23 | Meghalaya | 2964007
24 | Manipur*β* | 2721756
25 | Nagaland | 1980602
26 | Goa | 1457723
27 | Arunachal Pradesh | 1382611
28 | Mizoram | 1091014
29 | Sikkim | 607688
30 | Delhi | 16753235
31 | Puducherry | 1244464
32 | Chandigarh | 1054686
33 | Andaman and Nicobar Islands | 379944
34 | Dadra and Nagar Haveli | 342853
35 | Daman and Diu | 242911
36 | Lakshadweep | 64429
事故表:
state | eqto8 | eqto10 | mrthn10 | ntknwn | total
-----------------------------+-------+--------+---------+--------+--------
Andhra Pradesh | 6425 | 8657 | 8144 | 19298 | 42524
Arunachal Pradesh | 88 | 76 | 87 | 0 | 251
Assam | 0 | 0 | 0 | 6535 | 6535
Bihar | 2660 | 3938 | 3722 | 0 | 10320
Chhattisgarh | 2888 | 7052 | 3571 | 0 | 13511
Goa | 616 | 1512 | 2184 | 0 | 4312
Gujarat | 4864 | 7864 | 7132 | 8089 | 27949
Haryana | 3365 | 2588 | 4112 | 0 | 10065
Himachal Pradesh | 276 | 626 | 977 | 1020 | 2899
Jammu and Kashmir | 1557 | 618 | 434 | 4100 | 6709
Jharkhand | 1128 | 701 | 1037 | 2845 | 5711
Karnataka | 11167 | 14715 | 18566 | 0 | 44448
Kerala | 5580 | 13271 | 17323 | 0 | 36174
Madhya Pradesh | 15630 | 16226 | 19354 | 0 | 51210
Maharashtra | 4117 | 5350 | 10538 | 46311 | 66316
Manipur | 147 | 453 | 171 | 0 | 771
Meghalaya | 210 | 154 | 119 | 0 | 483
Mizoram | 27 | 58 | 25 | 0 | 110
Nagaland | 11 | 13 | 18 | 0 | 42
Odisha | 1881 | 3120 | 4284 | 0 | 9285
Punjab | 1378 | 2231 | 1825 | 907 | 6341
Rajasthan | 5534 | 5895 | 5475 | 6065 | 22969
Sikkim | 6 | 144 | 8 | 0 | 158
Tamil Nadu | 8424 | 18826 | 29871 | 10636 | 67757
Tripura | 290 | 376 | 222 | 0 | 888
Uttarakhand | 318 | 305 | 456 | 393 | 1472
Uttar Pradesh | 8520 | 10457 | 10995 | 0 | 29972
West Bengal | 1494 | 1311 | 974 | 8511 | 12290
Andaman and Nicobar Islands | 18 | 104 | 114 | 0 | 236
Chandigarh | 112 | 39 | 210 | 58 | 419
Dadra and Nagar Haveli | 40 | 20 | 17 | 8 | 85
Daman and Diu | 11 | 6 | 8 | 25 | 50
Delhi | 0 | 0 | 0 | 6937 | 6937
Lakshadweep | 0 | 0 | 0 | 3 | 3
Puducherry | 154 | 668 | 359 | 0 | 1181
All India | 88936 | 127374 | 152332 | 121741 | 490383
所以结果应该是
21.57
81.03
107.44
解释:
事故发生率最高的州是泰米尔纳德邦、马哈拉施特拉邦和中央邦。
Tamilnadu population/accidents = 21213/983 = 21.57 (Assumed values)
Maharasthra population/accidents = 10000/123 = 81.03
Madhyapradesh population/accidents = 34812/324 = 107.44
我的查询是:
SELECT POPULATION/
(SELECT TOTAL
FROM accidents
WHERE STATE NOT LIKE 'All %'
ORDER BY TOTAL DESC
LIMIT 3)
aVG FROM population
WHERE STATE IN
(SELECT STATE
FROM accidents
WHERE STATE NOT LIKE 'All %'
ORDER BY TOTAL DESC
LIMIT 3);
抛出错误:用作表达式的子查询返回多于一行。
如何修改查询以获得所需的结果或任何其他方式在 postgresql 中获得结果？
最佳答案
这应该可以做到。
SELECT a.state, population.population/a.total FROM
(SELECT total, state FROM accidents WHERE state <> 'All India' ORDER BY total DESC LIMIT 3 ) AS a
INNER JOIN population on a.state = population.state
关于postgresql - 来自 postgresql 查询的具有多个结果的除法，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37249764/