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 |
+----+------+--------------+
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“*”)
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“*”)