查找一个 MySQL 表中不存在于另一个表中的记录？

mysql> CREATE table PresentHistory
-> (
-> HisID int,
-> HisName varchar(100)
-> );
Query OK, 0 rows affected (0.54 sec)

mysql> INSERT into PresentHistory values(1,'John');
Query OK, 1 row affected (0.13 sec)

mysql> INSERT into PresentHistory values(2,'Bob');
Query OK, 1 row affected (0.15 sec)

mysql> SELECT * from PresentHistory;

+-------+---------+
| HisID | HisName |
+-------+---------+
| 1     | John    |
| 2     | Bob     |
+-------+---------+
2 rows in set (0.00 sec)

mysql> CREATE table PastHistory
-> (
-> PastId int,
-> PastName varchar(100)
-> );
Query OK, 0 rows affected (0.74 sec)

mysql> INSERT into PastHistory values(1,'John');
Query OK, 1 row affected (0.13 sec)

mysql> INSERT into PastHistory values(2,'Bob');
Query OK, 1 row affected (0.13 sec)

mysql> INSERT into PastHistory values(3,'Carol');
Query OK, 1 row affected (0.17 sec)

mysql> INSERT into PastHistory values(4,'Jason');
Query OK, 1 row affected (0.16 sec)

mysql> SELECT * from PastHistory;

+--------+----------+
| PastId | PastName |
+--------+----------+
| 1      | John     |
| 2      | Bob      |
| 3      | Carol    |
| 4      | Jason    |
+--------+----------+
4 rows in set (0.00 sec)

SELECT * from yourSecondTableName where columnNamefromSecondtable NOT IN
(SELECT columnNamefromfirsttable from yourFirstTableName);

mysql> SELECT * from PastHistory where PastName not in (select HisName from
PresentHistory);

+--------+----------+
| PastId | PastName |
+--------+----------+
| 3      | Carol    |
| 4      | Jason    |
+--------+----------+
2 rows in set (0.00 sec)