需要幫助從Oracle表

Question

獲得價值我有2個表

表1

Name  City 
-------------------- 
Deep  Delhi 
Manu  Atlanta 
Raju  PanamaCity 

表2

City 
----- 
Delhi 

我想補充的結果稱爲 「國家」 的另一列所以最後的結果會像

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因此，如果第一臺城市列的值匹配，則新列的值應該「已知」

Answer 1

上Joins和case語句讀了

SELECT t1.name, 
    t2.city, 
    case t2.city is NULL then 'Unknown' else 'Known' end as Country 
FROM table1 t1 
LEFT JOIN table2 t2 
on t1.city = t2.city 

樣機：

Select t1.name, 
    t1.city, 
    case when t2.city is NULL then 'Unknown' else 'Known' end as Country 
FROM (
    select 'Deep' as Name, 'Dehli' as city from dual UNION 
    select 'Manu' as Name, 'Atlanta' as city from dual UNION 
    select 'Raju' as Name, 'PanamaCity' as city from dual) t1 
LEFT JOIN 
(select 'Dehli' as city from dual) 
    t2 
    on t1.city=t2.city 

results in: 
Name City  Country 
Deep Dehli  Known 
Manu Atlanta  Unknown 
Raju PanamaCity Unknown