我有以下两个表(在MySQL):

Phone_book
+----+------+--------------+
| id | name | phone_number |
+----+------+--------------+
| 1  | John | 111111111111 |
+----+------+--------------+
| 2  | Jane | 222222222222 |
+----+------+--------------+

Call
+----+------+--------------+
| id | date | phone_number |
+----+------+--------------+
| 1  | 0945 | 111111111111 |
+----+------+--------------+
| 2  | 0950 | 222222222222 |
+----+------+--------------+
| 3  | 1045 | 333333333333 |
+----+------+--------------+

我如何找出哪些电话是由电话号码不在电话簿中的人打的?期望的输出将是:

Call
+----+------+--------------+
| id | date | phone_number |
+----+------+--------------+
| 3  | 1045 | 333333333333 |
+----+------+--------------+

当前回答

我认为

SELECT CALL.* FROM CALL LEFT JOIN Phone_book ON 
CALL.id = Phone_book.id WHERE Phone_book.name IS NULL

其他回答

SELECT DISTINCT Call.id 
FROM Call 
LEFT OUTER JOIN Phone_book USING (id) 
WHERE Phone_book.id IS NULL

这将返回Phone_book表中缺少的额外id。

SELECT Call.ID, Call.date, Call.phone_number 
FROM Call 
LEFT OUTER JOIN Phone_Book 
  ON (Call.phone_number=Phone_book.phone_number) 
  WHERE Phone_book.phone_number IS NULL

应该删除子查询,允许查询优化器发挥它的魔力。

另外,避免使用“SELECT *”,因为如果有人更改了底层表或视图,它会破坏代码(而且效率很低)。

我认为

SELECT CALL.* FROM CALL LEFT JOIN Phone_book ON 
CALL.id = Phone_book.id WHERE Phone_book.name IS NULL

当处理更大的数据集时,下面的代码将比上面给出的答案更有效一些。

SELECT *
FROM Call
WHERE NOT EXISTS (
    SELECT 'x'
    FROM Phone_book
    WHERE Phone_book.phone_number = Call.phone_number
);

有几种不同的方法来做到这一点,不同的效率,这取决于你的查询优化器有多好,以及你的两个表的相对大小:

这是最短的语句,如果你的电话簿很短,可能是最快的:

SELECT  *
FROM    Call
WHERE   phone_number NOT IN (SELECT phone_number FROM Phone_book)

或者(感谢Alterlife)

SELECT *
FROM   Call
WHERE  NOT EXISTS
  (SELECT *
   FROM   Phone_book
   WHERE  Phone_book.phone_number = Call.phone_number)

或者(感谢WOPR)

SELECT * 
FROM   Call
LEFT OUTER JOIN Phone_Book
  ON (Call.phone_number = Phone_book.phone_number)
  WHERE Phone_book.phone_number IS NULL

(忽略这一点,正如其他人所说,通常最好只选择你想要的列,而不是“*”)