如何合併SQL中的兩個表？

Question

我有兩個表：

Table 1 = idhash - username - usermail 
Table 2 = idhash - views - fistseen - lastseen 

現在我想這些表合併到一個新表：

Table 3 = idhash - username - usermail - firstseen - lastseen 

*請注意，我要刪除的意見欄。

我試過了我在google上找到的解決方案，但到目前爲止他們似乎沒有工作。

• 並非所有從表2中的idhash列有相應idhash表1 Stiil存儲那些「錯配」行空的用戶名和usermail

Answer 1

該查詢會給你的結果：

SELECT A.*, B.firstseen, B.lastseen 
FROM [Table 1] A 
LEFT JOIN [Table 2] B 
ON A.idhash = B.idhash 

並插入和更新在你的表3的結果：

INSERT INTO [Table 3](idhash, username, usermail, firstseen, lastseen) 
SELECT A.*, B.firstseen, B.lastseen 
FROM [Table 1] A 
LEFT JOIN [Table 2] B 
ON A.idhash = B.idhash 
LEFT JOIN [Table 3] C 
ON A.idhash = C.idhash 
WHERE C.idhash IS NULL 

-- For SQL Server 
UPDATE T3 
SET firstseen = T1.firstseen, 
    lastseen = T1.lastseen 
FROM [Table 3] T3 
INNER JOIN (SELECT A.*, B.firstseen, B.lastseen 
      FROM [Table 1] A 
      LEFT JOIN [Table 2] B 
      ON A.idhash = B.idhash) T1 
WHERE T3.firstseen != T1.firstseen OR T3.lastseen != T1.lastseen 

Answer 2

你可能只是蠻力它與您選擇的編程語言。只需構建一個新表，查詢兩個表，以編程方式連接行，但需要連接，插入到新表中。

Answer 3

insert into table3 
select t1.idhash, t1.username, t1.usermail, t2.firstseen,t2.lastseen 
from table1 t1 left join table2 t2 on t1.idhas=t2.idhas 

Answer 4

這應該是一個良好的開端。您需要告訴我們如何處理您的錯誤匹配記錄，然後才能提供更具體的信息。

Select 
    table1.idhash 
    ,username 
    ,usermail 
    ,firstseen 
    ,lastseen 
From table1 
    left join table2 
     on table1.idhash = table2.idhash 

Answer 5

與字段類型在創建語句

http://www.w3schools.com/sql/sql_create_table.asp

創建新表，然後做一個insert Into Table3 <yourtable> select a.f1,b.f2,c.f3 from Table1 a, Table 2 b on a.id = b.id

Answer 6

這是非常接近蠻力。

select coalesce(t1.idhash, t2.idhash) as idhash 
, username 
, usermail 
, firstseen 
, lastseen 
into table3 
from table1 t1 
cross join table2 t2 

Answer 7

試試這個：

INSERT INTO table3 (idhash, username, usermail, firstseen, lastseen) 
SELECT a.idhash, a.username, a.usermail, 
     b.firstseen, b.lastseen 
FROM table1 a LEFT JOIN table2 b 
      ON a.idhash = b.idhash 

Answer 8

我這樣做：

  CREATE TABLE table3 
        AS 
       SELECT idhash, username, usermail, firstseen, lastseen 
        FROM Table1 
NATURAL FULL OUTER JOIN Table2 

Answer 9

下面是MySQL的一個解決方案：

CREATE TABLE table3 
// First get all the rows from table2, paired with matching rows from table1 
(SELECT a.idhash, b.username, b.usermail, a.firstseen, a.lastseen 
FROM table2 a 
LEFT JOIN table1 b 
    ON b.idhash = a.idhash) 
// Now get the remaining rows from table1 that don't have matches 
UNION ALL 
(SELECT null, a.username, a.usermail, null, null 
FROM table1 a 
LEFT JOIN table2 b 
    ON b.idhash = a.idhash 
WHERE b.idhash IS NULL) 

如果你不想讓行來自table1，在table2中沒有相應的行，然後刪除UNION子句中的第二個查詢。