SQL基础语法—insert语句

1 insert语句

insert语句用于插入数据到表中，其基本语法有以下三种：

Syntax:
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [(col_name [, col_name] ...)]
    {VALUES | VALUE} (value_list) [, (value_list)] ...
    [ON DUPLICATE KEY UPDATE assignment_list]

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    SET assignment_list
    [ON DUPLICATE KEY UPDATE assignment_list]

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [(col_name [, col_name] ...)]
    SELECT ...
    [ON DUPLICATE KEY UPDATE assignment_list]

• 其中 select...values和 insert...set两种语句都是将指定的数据插入到现成的表中，而insert...select语句是将另外表中数据查出来并插入到现成的表中

• partiion子句代表可以将数据插入到指定的表分区中

• table_name代表将数据插入到的目标表

• col_name 代表要插入指定数据的目标表列，如果是多列则用逗号隔开，如果目标表中的某些列没有在insert语句中指定，则这些列会插入默认值，当然可以使用default显式指定插入默认值

• values中除了可以指定确定的数值之外，开可以使用表达式expr

insert into tbl_name (col1,col2) values(15,col1*2)	##正确
insert into tbl_name (col1,col2) values(col1*2,15)	##错误

案例演示：

## 修改sid字段，添加auto_increment属性
mysql> alter table students modify sid int auto_increment;
Query OK, 2 rows affected (0.23 sec)
Records: 2  Duplicates: 0  Warnings: 0

## 修改gender字段，添加默认值0
mysql> alter table students modify gender int default 0;
Query OK, 0 rows affected (0.08 sec)
Records: 0  Duplicates: 0  Warnings: 0

## 向students表中插入一条数据
mysql> insert into students(sname) values("bbb");
Query OK, 1 row affected (0.04 sec)

mysql> insert into students(sid,sname) values(5,"ccc");
Query OK, 1 row affected (0.02 sec)

mysql> insert into students(sname) values("ddd");
Query OK, 1 row affected (0.07 sec)

mysql> insert into students(sid,sname) values(4,"dd");
Query OK, 1 row affected (0.10 sec)

mysql> insert into students values(3*3,'fff',1);
Query OK, 1 row affected (0.09 sec)

mysql> select * from students;
+-----+--------+--------+
| sid | sname  | gender |
+-----+--------+--------+
|   1 | viktor |      1 |
|   2 | aaa    |   NULL |
|   3 | bbb    |      0 |
|   4 | dd     |      0 |
|   5 | ccc    |      0 |
|   6 | ddd    |      0 |
|   9 | fff    |      1 |
+-----+--------+--------+
7 rows in set (0.00 sec)

• inset...values语句不光可以插入一条数据，也可以插入多条数据

insert into tbl_name(a,b,c) values(1,2,3)(4,5,6)
insert into students values(7,'abc'),(8,'bcd')

• low_priority关键词代表如果有其他链接正在读取目标表数据，则此insert语句需要等待读取完成

• low_priority和high_priority关键词仅在MylSAM，MEMORY， MERGE三种存储引擎下才生效

• ignore关键词代表insert语句如果违反主键和伪意见的约束条件，则不报错而只产生警告信息，违反的行被丢弃，而不是整个语句回退；在数据类型转换有问题时如果有ignore则只产生警告信息，而不是语句回退

mysql> select * from students;
+-----+--------+--------+
| sid | sname  | gender |
+-----+--------+--------+
|   1 | viktor |      1 |
|   2 | aaa    |   NULL |
|   3 | bbb    |      0 |
|   4 | dd     |      0 |
|   5 | ccc    |      0 |
|   6 | ddd    |      0 |
|   9 | fff    |      1 |
+-----+--------+--------+
7 rows in set (0.00 sec)

mysql> insert ignore into students values(1,'aa',1),(7,'cc',0);
Query OK, 1 row affected, 1 warning (0.10 sec)
Records: 2  Duplicates: 1  Warnings: 1

2 insert... select语句

用于从另外的表中查出记录并插入到目标表中

insert into tbl_temp2(fld_id)
	select tbl_temp1.fld_order_id
	from tbl_temp1 where tbl_temp1.fld_order_id > 100;

当目标表和select语句中的表相同时，则会先将select语句的结果存放在临时表中，再插入到目标表中（注意执行顺序）

mysql> desc student2;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sid   | int(11)     | NO   |     | NULL    |       |
| sname | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> desc students;
+--------+-------------+------+-----+---------+----------------+
| Field  | Type        | Null | Key | Default | Extra          |
+--------+-------------+------+-----+---------+----------------+
| sid    | int(11)     | NO   | PRI | NULL    | auto_increment |
| sname  | varchar(20) | NO   | UNI | NULL    |                |
| gender | int(11)     | YES  |     | 0       |                |
+--------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

## concat用来合并两个字段
mysql> insert into student2(sid,sname) select sid,concat(sid,sname) from students where sid=1;
Query OK, 1 row affected (0.07 sec)
Records: 1  Duplicates: 0  Warnings: 0

## 当两个表中的字段不匹配时，插入会出现错误
mysql> insert into student2 select * from students;
ERROR 1136 (21S01): Column count doesn't match value count at row 1

##选定两个字段进行插入
mysql> insert into student2 select sid,sname from students;
Query OK, 8 rows affected (0.07 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql> select * from student2;
+-----+---------+
| sid | sname   |
+-----+---------+
|   1 | 1viktor |
|   2 | aaa     |
|   3 | bbb     |
|   7 | cc      |
|   5 | ccc     |
|   4 | dd      |
|   6 | ddd     |
|   9 | fff     |
|   1 | viktor  |
+-----+---------+
9 rows in set (0.00 sec)

3 insert on duplicate key update语句

当insert语句中使用on duplicate key update子句时，如果碰到当前插入的数据违反主键或唯一键的唯一性约束，则insert会转变成update语句修改对应的已经存在表中的这条数据。比如，如果a字段有唯一性约束且已经含有1这样的记录，则以下两条语句的执行结果相同。

insert into table(a,b,c) values(1,2,3)
	on duplicate key update c=c+1
update table set c=c+1 where a=1;

简而言之，该语句可以解决插入的数据与表之间的冲突。

案例演示：

mysql> insert into student2(sid,sname) select sid,sname from students where sid<3;
Query OK, 2 rows affected (0.08 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from student2;
+-----+--------+
| sid | sname  |
+-----+--------+
|   1 | viktor |
|   2 | aaa    |
+-----+--------+
2 rows in set (0.00 sec)

## 创建sname字段的unique索引
mysql> create unique index idx_1 on student2(sname);
Query OK, 0 rows affected (0.08 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student2;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sid   | int(11)     | NO   |     | NULL    |       |
| sname | varchar(20) | YES  | UNI | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> insert into student2(sid,sname) select sid,sname from students where sid=1;
ERROR 1062 (23000): Duplicate entry 'viktor' for key 'idx_1'
mysql> insert into student2(sid,sname) select sid,sname from students where sid=1 on duplicate key update sname='dabric';
Query OK, 2 rows affected (0.01 sec)
Records: 1  Duplicates: 1  Warnings: 0

mysql> select * from student2;
+-----+--------+
| sid | sname  |
+-----+--------+
|   1 | dabric |
|   2 | aaa    |
+-----+--------+
2 rows in set (0.00 sec)

mysql> insert into student values(1,'bb',0) on duplicate key update sname='b'sex=1;

4 练习

• 将如下数据插入到dept表中

1,'computer science'; 2,'education'; 4,'accounting'

• 根据create table...like语句创建teacher_backup表，并插入如下数据：

1,'susan'; 1; 2,'ruth'; 4; 3,'vivian', 4

• 将teacher_backup表的数据通过insert...select语句插入到teacher表中