表的複製:
語法：create table 表名 as select語句；
將查詢結果當做表建立出來。
將查詢結果插入到一張表中：
insert into dept1 select * from dept;
將一張表中的dept查詢結果當做資料插入前面表中
修改資料：update（注意當中標點符號）
語法格式：update 表名 欄位名1=值1，欄位名2=值2。。。where 條件；
注意沒有條件整張表資料全部更新。
mysql> select * from t_student;
+------+------+------+------------+----------+
| no | name | *** | classno | birth |
+------+------+------+------------+----------+
| null | zs | 1 | null | null |
| 1 | jack | 0 | gaosan2ban | 2021-2-5 |
| 2 | rose | 1 | gs2b | 2021-2-5 |
| 3 | abc | 1 | gs2b | 2021-2-5 |
+------+------+------+------------+----------+
4 rows in set (0.00 sec)
mysql> update t_student set name='aaa',***='0' where no=3;
query ok, 1 row affected (0.01 sec)
rows matched: 1 changed: 1 warnings: 0
mysql> select * from t_student;
+------+------+------+------------+----------+
| no | name | *** | classno | birth |
+------+------+------+------------+----------+
| null | zs | 1 | null | null |
| 1 | jack | 0 | gaosan2ban | 2021-2-5 |
| 2 | rose | 1 | gs2b | 2021-2-5 |
| 3 | aaa | 0 | gs2b | 2021-2-5 |
+------+------+------+------------+----------+
update t_student set classno=『da4』,birth=『2021-2-6』;
mysql> update t_student set classno='da4',birth='2021-2-6';
query ok, 4 rows affected (0.01 sec)
rows matched: 4 changed: 4 warnings: 0
mysql> select * from t_student;
+------+------+------+---------+----------+
| no | name | *** | classno | birth |
+------+------+------+---------+----------+
| null | zs | 1 | da4 | 2021-2-6 |
| 1 | jack | 0 | da4 | 2021-2-6 |
| 2 | rose | 1 | da4 | 2021-2-6 |
| 3 | aaa | 0 | da4 | 2021-2-6 |
+------+------+------+---------+----------+
語法格式：delete from 表名 where 條件；
注意：沒有條件全部刪除。
mysql> select * from t_student;
+------+------+------+---------+----------+
| no | name | *** | classno | birth |
+------+------+------+---------+----------+
| null | zs | 1 | da4 | 2021-2-6 |
| 1 | jack | 0 | da4 | 2021-2-6 |
| 2 | rose | 1 | da4 | 2021-2-6 |
| 3 | aaa | 0 | da4 | 2021-2-6 |
+------+------+------+---------+----------+
4 rows in set (0.00 sec)
mysql> delete from t_student where no=1;
query ok, 1 row affected (0.01 sec)
mysql> select * from t_student;
+------+------+------+---------+----------+
| no | name | *** | classno | birth |
+------+------+------+---------+----------+
| null | zs | 1 | da4 | 2021-2-6 |
| 2 | rose | 1 | da4 | 2021-2-6 |
| 3 | aaa | 0 | da4 | 2021-2-6 |
+------+------+------+---------+----------+
mysql> select * from t_student;
+------+------+------+---------+----------+
| no | name | *** | classno | birth |
+------+------+------+---------+----------+
| null | zs | 1 | da4 | 2021-2-6 |
| 2 | rose | 1 | da4 | 2021-2-6 |
| 3 | aaa | 0 | da4 | 2021-2-6 |
+------+------+------+---------+----------+
3 rows in set (0.00 sec)
mysql> delete from t_student where name='zs';
query ok, 1 row affected (0.01 sec)
mysql> select * from t_student;
+------+------+------+---------+----------+
| no | name | *** | classno | birth |
+------+------+------+---------+----------+
| 2 | rose | 1 | da4 | 2021-2-6 |
| 3 | aaa | 0 | da4 | 2021-2-6 |
+------+------+------+---------+----------+
select * from 表名；
怎麼刪除大表？（重點）
truncate table 表名；//表被截斷，不可回滾，永久丟失
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