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汽車大全
mysql一道麵試題
mysql> #一道麵試題
mysql> #把一張表num 的值[20-30]之間的數全改為20
mysql> #並且把[30-40]之間的數全改為30
mysql> create table mianshi (
-> num int
-> );
Query OK, 0 rows affected (1.94 sec)
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| class |
| m |
| mianshi |
| msg |
| snsmember |
| test1 |
+----------------+
6 rows in set (0.52 sec)
mysql> insert into mianshi
-> values(3),(8),(12),(15),(21),(25),(26),(32),(33),(39),(43),(52);
Query OK, 12 rows affected (0.22 sec)
Records: 12 Duplicates: 0 Warnings: 0
mysql> desc mianshi;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| num | int(11) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
1 row in set (0.20 sec)
mysql> select * from mianshi;
+------+
| num |
+------+
| 3 |
| 8 |
| 12 |
| 15 |
| 21 |
| 25 |
| 26 |
| 32 |
| 33 |
| 39 |
| 43 |
| 52 |
+------+
12 rows in set (0.01 sec)
mysql> #把num當成變量看，因此num/10取整，再乘以10
mysql> update mianshi set num=floor(num/10)*10
-> where num>=20 and num<=39;
Query OK, 6 rows affected (0.59 sec)
Rows matched: 6 Changed: 6 Warnings: 0
mysql> select * from mianshi;
+------+
| num |
+------+
| 3 |
| 8 |
| 12 |
| 15 |
| 20 |
| 20 |
| 20 |
| 30 |
| 30 |
| 30 |
| 43 |
| 52 |
+------+
12 rows in set (0.00 sec)
mysql> exit
最後更新：2017-04-04 07:03:20