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»¹ÊÇÄÇ2¸ö±í T1(id title number) T2£¨id tid ¡£¡££© tidΪÍâ¼ü ¹ØÁªt1±íid
ÏÖÔÚÏëÔÚɾ³ýt2±í¼Ç¼ʱ ¸üÐÂt1±ínumber£¨numberΪt2±íÔÚt1±í¶ÔÓ¦µÄ×ÜÊý t2.tid=t1.id £¬Ìû×ÓºÍÌû×ӻظ´µÄ¹ØÏµ£©
ÎÊÌâµÄµØ·½ÔÚÓÚ t2±íÔÚɾ³ýʱ ÊÇÅúÁ¿É¾³ý¼Ç¼ Ôõôд´¥·¢Æ÷£¿
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SQL code:
mysql> select * from t1;
+------+-------+--------+
| id | title | number |
+------+-------+--------+
| 1 | a | 1 |
| 2 | b | 0 |
+------+-------+--------+
2 rows in set (0.00 sec)
mysql> select * from t2;
+------+------+-------+
| id | tid | title |
+------+------+-------+
| 1 | 1 | A |
+------+------+-------+
1 row in set (0.00 sec)
mysql> insert into t2 values
-> (2,1,'A'),
-> (3,1,'A'),
-> (4,1,'A'),
-> (5,1,'A'),
-> (6,1,'A'),
-> (7,2,'B'),
-> (8,2,'B'),
-> (9,2,'B'),
-> (10,2,'B'),
-> (11,2,'B');
Query OK, 10 rows affected (0.06 sec)
Records: 10 Duplicates: 0 Warnings: 0
mysql> select * from t1;
+------+-------+--------+
| id | title | number |
+------+-------+--------+
| 1 | a | 6 |
| 2 | b | 5 |
+------+-------+--------+
2 rows in set (
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