[英]How do I add a column from a different table, to the results of an existing query in sql?
我有兩張表 CHICAGO_CRIME_DATA 和 CENSUS_DATA。
我正在運行以下查詢:
select count(id) as NUM_OF_CRIMES, COMMUNITY_AREA_NUMBER
from CHICAGO_CRIME_DATA
group by COMMUNITY_AREA_NUMBER
order by NUM_OF_CRIMES desc
limit 1;
返回包含兩列的結果:
具有各自的值:
我現在想從 CENSUS_DATA 向該結果添加一個名為 COMMUNITY_AREA_NAME 的列,其中 COMMUNITY_AREA_NUMBER = 25。
列 COMMUNITY_AREA_NUMBER 在兩個表中。
我對 sql 非常陌生,並且嘗試了各種使用別名的子查詢和隱式連接的實現,但不知道如何做到這一點,任何幫助將不勝感激!
謝謝
您可以運行子 select 在其中使用 CHICAGO_CRIME_DATA 的 COMMUNITY_AREA_NUMBER 鏈接兩個表
select count(id) as NUM_OF_CRIMES, COMMUNITY_AREA_NUMBER
,( SELECT COMMUNITY_AREA_NAME
from CENSUS_DATA where COMMUNITY_AREA_NUMBER = CHICAGO_CRIME_DATA.COMMUNITY_AREA_NUMBER) as COMMUNITY_AREA_NAME
from CHICAGO_CRIME_DATA
group by COMMUNITY_AREA_NUMBER
order by NUM_OF_CRIMES desc
limit 1;
或者你可以加入表格
select count(id) as NUM_OF_CRIMES, CHICAGO_CRIME_DATA.COMMUNITY_AREA_NUMBER
, MAX( COMMUNITY_AREA_NAME) as COMMUNITY_AREA_NAME
from CHICAGO_CRIME_DATA INNEr JOIN CENSUS_DATA ON CENSUS_DATA.COMMUNITY_AREA_NUMBER = CHICAGO_CRIME_DATA.COMMUNITY_AREA_NUMBER
group by CHICAGO_CRIME_DATA.COMMUNITY_AREA_NUMBER
order by NUM_OF_CRIMES desc
limit 1;
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