連接表沒有重複的行/ NULL值

Question

所以我有，我有合併時查詢但兩者join和union似乎並不去實現我的目標是什麼

聯盟的多個表：

mysql> SELECT NAME, currentstatus, NULL AS username, NULL AS status FROM statustable WHERE Name like '%ahsan%' UNION ALL SELECT NULL AS NAME, NULL AS currentstatus, username, status from awsaccount WHERE username like '%ahsan%'; 
+--------------+-------------------+----------+--------------------------------+ 
| NAME   | currentstatus  | status | username       | 
+--------------+-------------------+----------+--------------------------------+ 
| Ahsan Naseem | activated   | NULL  | NULL       | 
| NULL   | NULL    | ACTIVE | ahsan.naseem  | 
| NULL   | NULL    | INACTIVE | ahsantest      | 
| NULL   | NULL    | ACTIVE | ahsantest2      | 
| NULL   | NULL    | ACTIVE | ahsantestuserprofileupdate  | 
| NULL   | NULL    | INACTIVE | ahsantestuserprofileupdate_cli | 
| NULL   | NULL    | INACTIVE | decent.ahsan   | 
| NULL   | NULL    | INACTIVE | decent.ahsan_cli    | 
+--------------+-------------------+----------+--------------------------------+ 
8 rows in set (0.00 sec) 

加入：

mysql> select * from (select * from statustable where Name like '%ahsan%') as ab JOIN (select * from awsaccount where username like '%ahsan%') as asb;                  
    +--------------+-------------------+--------------------------------+----------+ 
    | Name   | currentstatus | username      | status | 
    +--------------+-------------------+--------------------------------+----------+ 
    | Ahsan Naseem | activated   | ahsan.naseem     | ACTIVE | 
    | Ahsan Naseem | activated   | ahsantest      | INACTIVE | 
    | Ahsan Naseem | activated   | ahsantest2      | ACTIVE | 
    | Ahsan Naseem | activated   | ahsantestuserprofileupdate  | ACTIVE | 
    | Ahsan Naseem | activated   | ahsantestuserprofileupdate_cli | INACTIVE | 
    | Ahsan Naseem | activated   | decent.ahsan   | INACTIVE | 
    | Ahsan Naseem | activated   | decent.ahsan_cli    | INACTIVE | 
    +--------------+-------------------+--------------------------------+----------+ 
    7 rows in set (0.00 sec) 

我想實現的是：

+--------------+-------------------+----------+--------------------------------+ 
| NAME   | currentstatus | status | username      | 
+--------------+-------------------+----------+--------------------------------+ 
| Ahsan Naseem | Active   | ACTIVE | ahsan.naseem  | 
| NULL   | NULL    | INACTIVE | ahsantest      | 
| NULL   | NULL    | ACTIVE | ahsantest2      | 
| NULL   | NULL    | ACTIVE | ahsantestuserprofileupdate  | 
| NULL   | NULL    | INACTIVE | ahsantestuserprofileupdate_cli | 
| NULL   | NULL    | INACTIVE | decent.ahsan  | 
| NULL   | NULL    | INACTIVE | decent.ahsan_cli    | 
+--------------+-------------------+----------+--------------------------------+ 

這真的有可能嗎？我是新來的sql，並會感謝您的意見和建議

Answer 1

請在將來提供表格定義和示例數據，這使得您的問題很可能會很快得到有用的答案。下面是我做了這些目的有一些變化的數據，讓我來回答你的問題：

DROP TABLE IF EXISTS statustable; 
CREATE TABLE statustable(`NAME` VARCHAR(32), currentStatus VARCHAR(32)); 

INSERT INTO statustable VALUES('Ahsan Naseem', 'activated'); 

DROP TABLE IF EXISTS awsaccount; 
CREATE TABLE awsaccount(`NAME` VARCHAR(32), username VARCHAR(32), `status` VARCHAR(32), logEntry DATETIME); 

INSERT INTO awsaccount VALUES('Ahsan Naseem', 'ACTIVE', 'ahsan.naseem', '2000-01-07'), 
    ('Ahsan Naseem', 'INACTIVE', 'ahsantest', '2000-01-06'), 
    ('Ahsan Naseem', 'ACTIVE', 'ahsantest2', '2000-01-05'), 
    ('Ahsan Naseem', 'ACTIVE', 'ahsantestuserprofileupdate', '2000-01-04'), 
    ('Ahsan Naseem', 'INACTIVE', 'ahsantestuserprofileupdate_cli', '2000-01-03'), 
    ('Ahsan Naseem', 'INACTIVE', 'decent.ahsan', '2000-01-02'), 
    ('Ahsan Naseem', 'INACTIVE', 'decent.ahsan_cli', '2000-01-01'); 

據我可以從你的樣品告訴查詢這裏有兩個問題，首先有沒有按在兩個表中似乎都不是公用密鑰，這是兩個表中與要匹配的行（連接/ JOIN）相同的值，對於彼此相關的行是相同的。 （順便說一下，這些數據類型也應該是相同的，否則查詢可能需要很長時間才能執行）。我在awsaccount表中添加了一個NAME列，使JOIN成爲可能。從這個結果像這樣：

SELECT A.`NAME`, A.currentStatus, B.username, B.`status` FROM 
    statusTable A 
RIGHT OUTER JOIN 
    awsaccount B 
ON A.`NAME` = B.`NAME`; 

+--------------+---------------+----------+--------------------------------+ 
| NAME   | currentStatus | username | status       | 
+--------------+---------------+----------+--------------------------------+ 
| Ahsan Naseem | activated  | ACTIVE | ahsan.naseem     | 
| Ahsan Naseem | activated  | INACTIVE | ahsantest      | 
| Ahsan Naseem | activated  | ACTIVE | ahsantest2      | 
| Ahsan Naseem | activated  | ACTIVE | ahsantestuserprofileupdate  | 
| Ahsan Naseem | activated  | INACTIVE | ahsantestuserprofileupdate_cli | 
| Ahsan Naseem | activated  | INACTIVE | decent.ahsan     | 
| Ahsan Naseem | activated  | INACTIVE | decent.ahsan_cli    | 
+--------------+---------------+----------+--------------------------------+ 
7 rows in set (0.00 sec) 

更接近您所需要的，但不能令人信服，因爲NAME關鍵是常見的兩個表中的所有條目。爲了產生一個輸出在你的問題中幾個步驟是必要的，我做了以下假設：

• 那awsaccout表是某種用戶的歷史，以前的戶頭雕像
• 爲此我已經添加了DATE字段可以被用來控制條目的順序進入該表

這意味着我們可以JOIN上ON子句只返回在NAME字段，使用子查詢（表C）來自的比賽在條目最新的情況下。由於您示例中的數據包含LEFT上的NULL列，因此我在此處使用了一個RIGHT OUTER JOIN，這是我遇到的代碼中遇到的不常見的JOINS之一。基本上，它說：回所有從第二個表（B）和第一（A）任何匹配的數據，否則，這些列是NULL

下面是結果：

SELECT A.`NAME`, A.currentStatus, B.username, B.`status` FROM 
    statusTable A 
RIGHT OUTER JOIN 
    awsaccount B 
ON A.`NAME` = B.`NAME` AND B.logEntry = (SELECT MAX(logEntry) FROM awsaccount WHERE `NAME` = A.`Name`); 

+--------------+---------------+----------+--------------------------------+ 
| NAME   | currentStatus | username | status       | 
+--------------+---------------+----------+--------------------------------+ 
| Ahsan Naseem | activated  | ACTIVE | ahsan.naseem     | 
| NULL   | NULL   | INACTIVE | ahsantest      | 
| NULL   | NULL   | ACTIVE | ahsantest2      | 
| NULL   | NULL   | ACTIVE | ahsantestuserprofileupdate  | 
| NULL   | NULL   | INACTIVE | ahsantestuserprofileupdate_cli | 
| NULL   | NULL   | INACTIVE | decent.ahsan     | 
| NULL   | NULL   | INACTIVE | decent.ahsan_cli    | 
+--------------+---------------+----------+--------------------------------+ 
7 rows in set (0.00 sec) 

正如你所提到的你的SQL新手，這裏是一張圖片，用於直觀地解釋不同種類的JOIN（取自here）。

問候，

詹姆斯