一文掌握MySQL基本查询操作_Mysql

前言

表的增删改查：
crud : create(创建), retrieve(读取)，update(更新)，delete（删除）

一、create

语法：

insert [into] table_name
[(column [, column] ...)]
values (value_list) [, (value_list)] ...
value_list: value, [, value] ...

创建一张表：

mysql> create table students(
    -> id int unsigned primary key auto_increment,
    -> sn int not null unique key comment "学号",
    ->  name varchar(20) not null,
    -> qq varchar(32) unique key
    -> );
query ok, 0 rows affected (0.02 sec)

单行数据 + 全列插入

value_list 数量必须和定义表的列的数量及顺序一致

mysql> insert into students values (66, 123, '刘备', 111111);
query ok, 1 row affected (0.00 sec)

多行数据 + 指定列插入

这里可以灵活插入

mysql> insert into students (sn, name) values (124, '关羽');
query ok, 1 row affected (0.00 sec)
mysql> insert into students (name, sn) values ('张飞', 125), ('曹操', 126), ('貂蝉', 128);
query ok, 1 row affected (0.00 sec)
mysql> select * from students;
+----+-----+--------+--------+
| id | sn  | name   | qq     |
+----+-----+--------+--------+
| 66 | 123 | 刘备   | 111111 |
| 67 | 124 | 关羽   | null   |
| 68 | 125 | 张飞   | null   |
| 69 | 126 | 曹操   | null   |
| 70 | 128 | 貂蝉   | null   |
+----+-----+--------+--------+
5 rows in set (0.00 sec)

插入否则更新

由于主键或者唯一键对应的值已经存在而导致插入失败：

mysql> insert into students values (70, 129, '西施', 22);
error 1062 (23000): duplicate entry '70' for key 'students.primary'
mysql> insert into students values (71, 129, '西施', 111111);
error 1062 (23000): duplicate entry '70' for key 'students.primary'

可以选择性的进行同步更新操作
语法：

insert ... on duplicate key update
	column = value [, column = value] ...

mysql> insert into students values (71 ,129, '西施', 111111) on duplicate key update id = 71, name = '西施', qq = 222222;
query ok, 2 rows affected (0.00 sec)
mysql> select * from students;
+----+-----+--------+--------+
| id | sn  | name   | qq     |
+----+-----+--------+--------+
| 67 | 124 | 关羽   | null   |
| 68 | 125 | 张飞   | null   |
| 69 | 126 | 曹操   | null   |
| 70 | 128 | 貂蝉   | null   |
| 71 | 123 | 西施   | 222222 |
+----+-----+--------+--------+
5 rows in set (0.00 sec)

替换

主键或者唯一键没有冲突，则直接插入；
主键或者唯一键如果冲突，则删除后再插入

mysql> replace into students (sn, name, qq) values (130, '吕布', 333333);
query ok, 1 row affected (0.00 sec)
mysql> replace into students (sn, name, qq) values (130, '吕布2', 333333);
query ok, 2 rows affected (0.00 sec)
-- 1 row affected: 表中没有冲突数据，数据被插入
-- 2 row affected: 表中有冲突数据，删除后重新插入
mysql> select * from students;
+----+-----+---------+--------+
| id | sn  | name    | qq     |
+----+-----+---------+--------+
| 67 | 124 | 关羽    | null   |
| 68 | 125 | 张飞    | null   |
| 69 | 126 | 曹操    | null   |
| 70 | 128 | 貂蝉    | null   |
| 71 | 123 | 西施    | 222222 |
| 73 | 130 | 吕布2   | 333333 |
+----+-----+---------+--------+
6 rows in set (0.00 sec)

二、retrieve

新建学生成绩表：

mysql> create table exam_result (
    -> id int unsigned primary key auto_increment,
    -> name varchar(20) not null comment '姓名',
    -> chinese float default 0.0 comment '语文成绩',
    -> math float default 0.0 comment '数学成绩',
    -> english float default 0.0 comment '英语成绩'
    -> );
query ok, 0 rows affected (0.01 sec)
mysql> insert into exam_result (name, chinese, math, english) values
    -> ('唐三藏', 67, 98, 56),
    -> ('孙悟空', 87, 78, 77),
    -> ('猪悟能', 88, 98, 90),
    -> ('曹孟德', 82, 84, 67),
    -> ('刘玄德', 55, 85, 45),
    -> ('孙权', 70, 73, 78),
    -> ('宋公明', 75, 65, 30);
query ok, 7 rows affected (0.00 sec)
records: 7  duplicates: 0  warnings: 0

select 列

全列查询

通常情况下不建议全列查询，一方面是传输的数据量可能非常大，而且可能会影响到索引的使用。

mysql> select * from exam_result;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  1 | 唐三藏    |      67 |   98 |      56 |
|  2 | 孙悟空    |      87 |   78 |      77 |
|  3 | 猪悟能    |      88 |   98 |      90 |
|  4 | 曹孟德    |      82 |   84 |      67 |
|  5 | 刘玄德    |      55 |   85 |      45 |
|  6 | 孙权      |      70 |   73 |      78 |
|  7 | 宋公明    |      75 |   65 |      30 |
+----+-----------+---------+------+---------+
7 rows in set (0.00 sec)

指定列查询

指定列的顺序可以自由选择

mysql> select name, chinese, id from exam_result;
+-----------+---------+----+
| name      | chinese | id |
+-----------+---------+----+
| 唐三藏    |      67 |  1 |
| 孙悟空    |      87 |  2 |
| 猪悟能    |      88 |  3 |
| 曹孟德    |      82 |  4 |
| 刘玄德    |      55 |  5 |
| 孙权      |      70 |  6 |
| 宋公明    |      75 |  7 |
+-----------+---------+----+
7 rows in set (0.00 sec)

查询字段为表达式

表达式不包含字段

mysql> select id, name, 10 from exam_result;
+----+-----------+----+
| id | name      | 10 |
+----+-----------+----+
|  1 | 唐三藏    | 10 |
|  2 | 孙悟空    | 10 |
|  3 | 猪悟能    | 10 |
|  4 | 曹孟德    | 10 |
|  5 | 刘玄德    | 10 |
|  6 | 孙权      | 10 |
|  7 | 宋公明    | 10 |
+----+-----------+----+
7 rows in set (0.00 sec)

表达式包含一个字段

mysql> select id, name, chinese + 100 from exam_result;
+----+-----------+---------------+
| id | name      | chinese + 100 |
+----+-----------+---------------+
|  1 | 唐三藏    |           167 |
|  2 | 孙悟空    |           187 |
|  3 | 猪悟能    |           188 |
|  4 | 曹孟德    |           182 |
|  5 | 刘玄德    |           155 |
|  6 | 孙权      |           170 |
|  7 | 宋公明    |           175 |
+----+-----------+---------------+
7 rows in set (0.00 sec)

表达式包含多个字段

mysql> select id, name, chinese + math + english from exam_result;
+----+-----------+--------------------------+
| id | name      | chinese + math + english |
+----+-----------+--------------------------+
|  1 | 唐三藏    |                      221 |
|  2 | 孙悟空    |                      242 |
|  3 | 猪悟能    |                      276 |
|  4 | 曹孟德    |                      233 |
|  5 | 刘玄德    |                      185 |
|  6 | 孙权      |                      221 |
|  7 | 宋公明    |                      170 |
+----+-----------+--------------------------+
7 rows in set (0.00 sec)

为查询结果指定别名

语法：

select column [as] alias_name [...] from table_name;

mysql> select id, name, chinese + math + english 总分 from exam_result;
+----+-----------+--------+
| id | name      | 总分   |
+----+-----------+--------+
|  1 | 唐三藏    |    221 |
|  2 | 孙悟空    |    242 |
|  3 | 猪悟能    |    276 |
|  4 | 曹孟德    |    233 |
|  5 | 刘玄德    |    185 |
|  6 | 孙权      |    221 |
|  7 | 宋公明    |    170 |
+----+-----------+--------+
7 rows in set (0.00 sec)

结果去重 distinct

distinct 必须紧跟在 select 之后，并且作用于所有选择的列。

数学成绩98分重复了：

mysql> select math from exam_result;
+------+
| math |
+------+
|   98 |
|   78 |
|   98 |
|   84 |
|   85 |
|   73 |
|   65 |
+------+
7 rows in set (0.00 sec)

去重：

mysql> select distinct math from exam_result;
+------+
| math |
+------+
|   98 |
|   78 |
|   84 |
|   85 |
|   73 |
|   65 |
+------+
6 rows in set (0.00 sec)

where条件

比较运算符：

逻辑运算符：

运算符优先级（从高到低）:

英语不及格的同学及英语成绩 ( < 60 )

mysql> select name, english from exam_result where english < 60;
+-----------+---------+
| name      | english |
+-----------+---------+
| 唐三藏    |      56 |
| 刘玄德    |      45 |
| 宋公明    |      30 |
+-----------+---------+
3 rows in set (0.00 sec)

语文成绩在 [80, 90] 分的同学及语文成绩

--使用and连接
mysql> select name, chinese from exam_result where chinese >= 80 and chinese <= 90;
+-----------+---------+
| name      | chinese |
+-----------+---------+
| 孙悟空    |      87 |
| 猪悟能    |      88 |
| 曹孟德    |      82 |
+-----------+---------+
3 rows in set (0.00 sec)
--使用between and 连接
mysql> select name, chinese from exam_result where chinese between 80 and 90;
+-----------+---------+
| name      | chinese |
+-----------+---------+
| 孙悟空    |      87 |
| 猪悟能    |      88 |
| 曹孟德    |      82 |
+-----------+---------+
3 rows in set (0.00 sec)

数学成绩是 58 或者 59 或者 98 或者 99 分的同学及数学成绩

--使用or连接
mysql> select name, math from exam_result where math = 58 or math = 59 or math = 98 or math = 99;
+-----------+------+
| name      | math |
+-----------+------+
| 唐三藏    |   98 |
| 猪悟能    |   98 |
+-----------+------+
2 rows in set (0.00 sec)
--使用in连接
mysql> select name, math from exam_result where math in (58, 59, 98, 99);
+-----------+------+
| name      | math |
+-----------+------+
| 唐三藏    |   98 |
| 猪悟能    |   98 |
+-----------+------+
2 rows in set (0.00 sec)

姓孙的同学及孙某同学

--姓孙的同学
mysql> select name from exam_result where name like ('孙%');
+-----------+
| name      |
+-----------+
| 孙悟空    |
| 孙权      |
+-----------+
2 rows in set (0.00 sec)
--孙某同学
mysql> select name from exam_result where name like ('孙_');
+--------+
| name   |
+--------+
| 孙权   |
+--------+
1 row in set (0.00 sec)

语文成绩好于英语成绩的同学

mysql> select name, chinese, english from exam_result where chinese > english;
+-----------+---------+---------+
| name      | chinese | english |
+-----------+---------+---------+
| 唐三藏    |      67 |      56 |
| 孙悟空    |      87 |      77 |
| 曹孟德    |      82 |      67 |
| 刘玄德    |      55 |      45 |
| 宋公明    |      75 |      30 |
+-----------+---------+---------+
5 rows in set (0.00 sec)

总分在 200 分以下的同学

别名不能用在 where 条件中

mysql> select name, chinese + math +english 总分 from exam_result where chinese + math + english < 200;
+-----------+--------+
| name      | 总分   |
+-----------+--------+
| 刘玄德    |    185 |
| 宋公明    |    170 |
+-----------+--------+
2 rows in set (0.00 sec)

语文成绩 > 80 并且不姓孙的同学

mysql> select name, chinese from exam_result where chinese > 80 and name not like ('孙%');
+-----------+---------+
| name      | chinese |
+-----------+---------+
| 猪悟能    |      88 |
| 曹孟德    |      82 |
+-----------+---------+
2 rows in set (0.00 sec)

孙姓同学，否则要求总成绩 > 200 并且语文成绩 < 数学成绩并且英语成绩 > 80

mysql> select name, chinese, math, english, chinese + math + english total from exam_result where name like ('孙%') or (chinese + math + english > 200 and chinese < math and english > 80);
+-----------+---------+------+---------+-------+
| name      | chinese | math | english | total |
+-----------+---------+------+---------+-------+
| 孙悟空    |      87 |   78 |      77 |   242 |
| 猪悟能    |      88 |   98 |      90 |   276 |
| 孙权      |      70 |   73 |      78 |   221 |
+-----------+---------+------+---------+-------+
3 rows in set (0.00 sec)

结果排序 order by

语法：
– asc 为升序（从小到大）
– desc 为降序（从大到小）
– 默认为 asc

select ... from table_name [where ...]
order by column [asc|desc], [...];

注意：在mysql中，没有 order by 子句的查询，返回的顺序是未定义的，永远不要依赖这个顺序

同学及数学成绩，按数学成绩升序显示

mysql> select name, math from exam_result order by math;
+-----------+------+
| name      | math |
+-----------+------+
| 宋公明    |   65 |
| 孙权      |   73 |
| 孙悟空    |   78 |
| 曹孟德    |   84 |
| 刘玄德    |   85 |
| 唐三藏    |   98 |
| 猪悟能    |   98 |
+-----------+------+
7 rows in set (0.00 sec)

查询同学各门成绩，依次按数学降序，英语升序，语文升序的方式显示

排序规则：
先按照第一个字段（math）排序，当第一个字段的值相同时，再按照第二个字段（english）排序，如果第二个字段也相同，则按照第三个字段（chinese）排序。

mysql> select name, math, english, chinese from exam_result order by math desc, english, chinese;
+-----------+------+---------+---------+
| name      | math | english | chinese |
+-----------+------+---------+---------+
| 唐三藏    |   98 |      56 |      67 |
| 猪悟能    |   98 |      90 |      88 |
| 刘玄德    |   85 |      45 |      55 |
| 曹孟德    |   84 |      67 |      82 |
| 孙悟空    |   78 |      77 |      87 |
| 孙权      |   73 |      78 |      70 |
| 宋公明    |   65 |      30 |      75 |
+-----------+------+---------+---------+
7 rows in set (0.00 sec)

查询同学及总分，由高到低

mysql> select name, chinese + math + english total from exam_result order by chinese + math + english desc;
+-----------+-------+
| name      | total |
+-----------+-------+
| 猪悟能    |   276 |
| 孙悟空    |   242 |
| 曹孟德    |   233 |
| 唐三藏    |   221 |
| 孙权      |   221 |
| 刘玄德    |   185 |
| 宋公明    |   170 |
+-----------+-------+
7 rows in set (0.00 sec)
--order by 字句中可以使用列别名
mysql> select name, chinese + math + english total from exam_result order by total desc;
+-----------+-------+
| name      | total |
+-----------+-------+
| 猪悟能    |   276 |
| 孙悟空    |   242 |
| 曹孟德    |   233 |
| 唐三藏    |   221 |
| 孙权      |   221 |
| 刘玄德    |   185 |
| 宋公明    |   170 |
+-----------+-------+
7 rows in set (0.00 sec)

查询姓孙的同学或者姓曹的同学数学成绩，结果按数学成绩由高到低显示

mysql> select name, math from exam_result where name like ('孙%') or name like ('曹%') order by math desc;
+-----------+------+
| name      | math |
+-----------+------+
| 曹孟德    |   84 |
| 孙悟空    |   78 |
| 孙权      |   73 |
+-----------+------+
3 rows in set (0.00 sec)

筛选分页结果 limit

语法：
– 起始下标为 0
– 从 0 开始，筛选 n 条结果
select … from table_name [where …] [order by …] limit n;

– 从 s 开始，筛选 n 条结果
select … from table_name [where …] [order by …] limit s, n;

– 从 s 开始，筛选 n 条结果，比第二种用法更明确，建议使用
select … from table_name [where …] [order by …] limit n offset s;

注意：
对未知表进行查询时，最好加一条 limit 1，避免因为表中数据过大，查询全表数据导致数据库卡死

按 id 进行分页，每页 3 条记录，分别显示第 1、2、3 页

--第1页
mysql> select * from exam_result order by id limit 0, 3;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  1 | 唐三藏    |      67 |   98 |      56 |
|  2 | 孙悟空    |      87 |   78 |      77 |
|  3 | 猪悟能    |      88 |   98 |      90 |
+----+-----------+---------+------+---------+
3 rows in set (0.00 sec)
--第2页
mysql> select * from exam_result order by id limit 3, 3;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  4 | 曹孟德    |      82 |   84 |      67 |
|  5 | 刘玄德    |      55 |   85 |      45 |
|  6 | 孙权      |      70 |   73 |      78 |
+----+-----------+---------+------+---------+
3 rows in set (0.00 sec)
--第3页
mysql> select * from exam_result order by id limit 6, 3;
+----+-----------+---------+------+---------+
| id | name      | chinese | math | english |
+----+-----------+---------+------+---------+
|  7 | 宋公明    |      75 |   65 |      30 |
+----+-----------+---------+------+---------+
1 row in set (0.00 sec)

三、update

语法：
对查询到的结果进行列值更新：

update table_name set column = expr [, column = expr ...]
	[where ...] [order by ...] [limit ...]

将孙悟空同学的数学成绩变更为 80 分

-- 查看原数据
select name, math from exam_result where name = '孙悟空';
+-----------+--------+
| name | math |
+-----------+--------+
| 孙悟空 | 78 |
+-----------+--------+
1 row in set (0.00 sec)
-- 数据更新
update exam_result set math = 80 where name = '孙悟空';
query ok, 1 row affected (0.04 sec)
rows matched: 1 changed: 1 warnings: 0
-- 查看更新后数据
select name, math from exam_result where name = '孙悟空';
+-----------+--------+
| name | math |
+-----------+--------+
| 孙悟空 | 80 |
+-----------+--------+
1 row in set (0.00 sec)

将曹孟德同学的数学成绩变更为 60 分，语文成绩变更为 70 分

-- 查看原数据
select name, math, chinese from exam_result where name = '曹孟德';
+-----------+--------+-------+
e | math | chinese |
+-----------+--------+-------+
| 曹孟德 | 84 | 82 |
+-----------+--------+-------+
1 row in set (0.00 sec)
-- 数据更新
update exam_result set math = 60, chinese = 70 where name = '曹孟德';
query ok, 1 row affected (0.14 sec)
rows matched: 1 changed: 1 warnings: 0
-- 查看更新后数据
select name, math, chinese from exam_result where name = '曹孟德';
+-----------+--------+-------+
| name | math | chinese |
+-----------+--------+-------+
| 曹孟德 | 60 | 70 |
+-----------+--------+-------+
1 row in set (0.00 sec)

将总成绩倒数前三的 3 位同学的数学成绩加上 30 分

-- 查看原数据
-- 别名可以在order by中使用
select name, math, chinese + math + english 总分 from exam_result order by 总分 limit 3;
+-----------+--------+--------+
| name | math | 总分 |
+-----------+--------+--------+
| 宋公明 | 65 | 170 |
| 刘玄德 | 85 | 185 |
| 曹孟德 | 60 | 197 |
+-----------+--------+--------+
3 rows in set (0.00 sec)
-- 数据更新，mysql不支持 math += 30 这种语法
update exam_result set math = math + 30 order by chinese + math + english limit 3;
-- 查看更新后数据
--这里还可以按总分升序排序取前 3 个
select name, math, chinese + math + english 总分 from exam_result where name in ('宋公明', '刘玄德', '曹孟德');
+-----------+--------+--------+
| name | math | 总分 |
+-----------+--------+--------+
| 曹孟德 | 90 | 227 |
| 刘玄德 | 115 | 215 |
| 宋公明 | 95 | 200 |
+-----------+--------+--------+
3 rows in set (0.00 sec)
-- 按总成绩排序后查询结果
select name, math, chinese + math + english 总分 from exam_result order by 总分 limit 3;
+-----------+--------+--------+
| name | math | 总分 |
+-----------+--------+--------+
| 宋公明 | 95 | 200 |
| 刘玄德 | 115 | 215 |
| 唐三藏 | 98 | 221 |
+-----------+--------+--------+
3 rows in set (0.00 sec)

将所有同学的语文成绩更新为原来的 2 倍

-- 查看原数据
select * from exam_result;
+----+-----------+-------+--------+--------+
| id | name | chinese | math | english |
+----+-----------+-------+--------+--------+
| 1 | 唐三藏 | 67 | 98 | 56 |
| 2 | 孙悟空 | 87 | 80 | 77 |
| 3 | 猪悟能 | 88 | 98 | 90 |
| 4 | 曹孟德 | 70 | 90 | 67 |
| 5 | 刘玄德 | 55 | 115 | 45 |
| 6 | 孙权 | 70 | 73 | 78 |
| 7 | 宋公明 | 75 | 95 | 30 |
+----+-----------+-------+--------+--------+
7 rows in set (0.00 sec)
-- 数据更新
update exam_result set chinese = chinese * 2;
query ok, 7 rows affected (0.00 sec)
rows matched: 7 changed: 7 warnings: 0
-- 查看更新后数据
select * from exam_result;
+----+-----------+-------+--------+--------+
| id | name | chinese | math | english |
+----+-----------+-------+--------+--------+
| 1 | 唐三藏 | 134 | 98 | 56 |
| 2 | 孙悟空 | 174 | 80 | 77 |
| 3 | 猪悟能 | 176 | 98 | 90 |
| 4 | 曹孟德 | 140 | 90 | 67 |
| 5 | 刘玄德 | 110 | 115 | 45 |
| 6 | 孙权 | 140 | 73 | 78 |
| 7 | 宋公明 | 150 | 95 | 30 |
+----+-----------+-------+--------+--------+
7 rows in set (0.00 sec)

四、delete

删除数据

语法：

delete from table_name [where ...] [order by ...] [limit ...]

删除孙悟空同学的考试成绩

-- 查看原数据
select * from exam_result where name = '孙悟空';
+----+-----------+-------+--------+--------+
| id | name | chinese | math | english |
+----+-----------+-------+--------+--------+
| 2 | 孙悟空 | 174 | 80 | 77 |
+----+-----------+-------+--------+--------+
1 row in set (0.00 sec)
-- 删除数据
delete from exam_result where name = '孙悟空';
query ok, 1 row affected (0.17 sec)
-- 查看删除结果
select * from exam_result where name = '孙悟空';
empty set (0.00 sec)

删除整张表数据

-- 准备测试表
create table for_delete (
id int primary key auto_increment,
name varchar(20)
);
query ok, 0 rows affected (0.16 sec)
-- 插入测试数据
insert into for_delete (name) values ('a'), ('b'), ('c');
query ok, 3 rows affected (1.05 sec)
records: 3 duplicates: 0 warnings: 0
-- 查看测试数据
select * from for_delete;
+----+------+
| id | name |
+----+------+
| 1 | a |
| 2 | b |
| 3 | c |
+----+------+
3 rows in set (0.00 sec)
-- 删除整表数据
delete from for_delete;
query ok, 3 rows affected (0.00 sec)
-- 查看删除结果
select * from for_delete;
empty set (0.00 sec)
-- 再插入一条数据，自增 id 在原值上增长
insert into for_delete (name) values ('d');
query ok, 1 row affected (0.00 sec)
-- 查看数据
select * from for_delete;
+----+------+
| id | name |
+----+------+
| 4 | d |
+----+------+
1 row in set (0.00 sec)
-- 查看表结构，会有 auto_increment=n 项
show create table for_delete\g
*************************** 1. row ***************************
table: for_delete
create table: create table `for_delete` (
`id` int(11) not null auto_increment,
`name` varchar(20) default null,
primary key (`id`)
) engine=innodb auto_increment=5 default charset=utf8
1 row in set (0.00 sec)

截断表：

语法：

truncate [table] table_name

注意：
这个操作慎重使用

只能对整表操作，不能像 delete 一样针对部分数据操作；
实际上 mysql 不对数据操作，所以比 delete 更快，但是truncate在删除数据的时候，并不经过真正的事物，所以无法回滚
会重置 auto_increment 项

-- 准备测试表
create table for_truncate (
id int primary key auto_increment,
name varchar(20)
);
query ok, 0 rows affected (0.16 sec)
-- 插入测试数据
insert into for_truncate (name) values ('a'), ('b'), ('c');
query ok, 3 rows affected (1.05 sec)
records: 3 duplicates: 0 warnings: 0
-- 查看测试数据
select * from for_truncate;
+----+------+
| id | name |
+----+------+
| 1 | a |
| 2 | b |
| 3 | c |
+----+------+
3 rows in set (0.00 sec)
-- 截断整表数据，注意影响行数是 0，所以实际上没有对数据真正操作
truncate for_truncate;
query ok, 0 rows affected (0.10 sec)
-- 查看删除结果
select * from for_truncate;
empty set (0.00 sec)
-- 再插入一条数据，自增 id 在重新增长
insert into for_truncate (name) values ('d');
query ok, 1 row affected (0.00 sec)
-- 查看数据
select * from for_truncate;
+----+------+
| id | name |
+----+------+
| 1 | d |
+----+------+
1 row in set (0.00 sec)
-- 查看表结构，会有 auto_increment=2 项
show create table for_truncate\g
*************************** 1. row ***************************
table: for_truncate
create table: create table `for_truncate` (
`id` int(11) not null auto_increment,
`name` varchar(20) default null,
primary key (`id`)
) engine=innodb auto_increment=2 default charset=utf8
1 row in set (0.00 sec)

插入查询结果

语法：

insert into table_name [(column [, column ...])] select ...

样例：
删除表中的的重复复记录，将 duplicate_table 的去重数据插入到 no_duplicate_table

-- 创建原数据表
create table duplicate_table (id int, name varchar(20));
query ok, 0 rows affected (0.01 sec)
-- 插入测试数据
insert into duplicate_table values
(100, 'aaa'),
(100, 'aaa'),
(200, 'bbb'),
(200, 'bbb'),
(200, 'bbb'),
(300, 'ccc');
query ok, 6 rows affected (0.00 sec)
records: 6 duplicates: 0 warnings: 0

-- 创建一张空表 no_duplicate_table，结构和 duplicate_table 一样
create table no_duplicate_table like duplicate_table;
query ok, 0 rows affected (0.00 sec)
-- 将 duplicate_table 的去重数据插入到 no_duplicate_table
insert into no_duplicate_table select distinct * from duplicate_table;
query ok, 3 rows affected (0.00 sec)
records: 3 duplicates: 0 warnings: 0
-- 通过重命名表，实现原子的去重操作
rename table duplicate_table to old_duplicate_table, no_duplicate_table to duplicate_table;
query ok, 0 rows affected (0.00 sec)
-- 查看最终结果
select * from duplicate_table;
+------+------+
| id | name |
+------+------+
| 100 | aaa |
| 200 | bbb |
| 300 | ccc |
+------+------+
3 rows in set (0.00 sec)
-- 删除备份表duplicate_table
drop table dulpicate_table;

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