合併多個相關行

Question

我有一個表Trackings(visitor_id, field, value, type)它記錄動態/用戶自定義字段

我要合併visitor A和visitor B，使得對於每一個在A跟蹤，將其覆蓋在B。換句話說，覆蓋所有的漏電痕跡在B與A相應的（它們不需要具有所有在合併中指定的相同的字段）

實施例：

visitor_id field   value  type 
A   name   Jack  string 
A   orders   5   integer 
B   orders   2   integer 
B   age    30   integer 
B   signed_up_at 1/1/1990 date  

合併訪問者A與乙應該產生

visitor_id field   value   type 
B   orders   5    integer 
B   age    30    integer 
B   signed_up_at 1/1/1990  date  
B   name   Jack 

理想的，這應該是相當高性能

任何想法？

Answer 1

你可以試試這個查詢看到部分結果

SELECT B.*, A.* 
FROM yourTable B 
FULL JOIN yourTable A 
    ON B.field = A.field 
AND B.visitor_id = 'B' 
AND A.visitor_id = 'A' 

SQL DEMO

SELECT 'B' as visitor_id, 
     COALESCE(A.field, B.field) as field, 
     COALESCE(A.value, B.value) as value, 
     COALESCE(A.type, B.type) as type 
FROM yourTable B 
FULL JOIN yourTable A 
    ON B.field = A.field 
AND B.visitor_id = 'B' 
AND A.visitor_id = 'A' 
WHERE B.visitor_id = 'B' 
    OR A.visitor_id = 'A' 

輸出