数据库表操作与列操作

一操作表
二操作数据行
作业

一操作表

增

? 语法：

? create table 表名（

? 字段名列类型 [可选的参数]，####记住加逗号

? 字段名列类型 [可选的参数]，#####记住加逗号

? 字段名列类型 [可选的参数] #####最后一行不加逗号

? ）charset = utf8; #####后面加分号

? 列约束（*******************************************）

? auto_increment：自增

? primary key 主键索引，加快查询速度，列的值不能重复

? not null 标识该字段不能为空

? default 为该字段设置默认值

? 例子1：
? create table t1(id int,name char(5))charest = utf8;

? Query OK, 0 rows affected (0.72 sec) #### 如果回显是queryok，代表创建成功

? 增加数据：

? 语法：
? insert into 表名（列1，列2）values（值1，’值2‘）;

? 例子：
? insert into t1(id,name) values(1,‘tank‘);

? insert into t1(id,name) values(1,‘tank2‘);

? 查询数据：
? 语法：
? select 列1，列2 from 表名（*代表查询所有的列）

? 列子：

? mysql>select * from t1;

                例子：
                        mysql> select * from t1;
                        +------+-------+
                        | id   | name  |
                        +------+-------+
                        |    1 | zekai |
                        +------+-------+
                        1 row in set (0.00 sec)

? 例子2：
? create table t2(id int auto_increment primary key,

? name char(10) )charset=utf8;

? 例子3（推荐）

? create table t3(

? id int unsigned auto_increment primary key,

? name char(10) not null default ‘xxx‘,

? age int not null default 0)charset = utf8;

? mysql>insert into t3(age) values(10);

? Query OK, 1 row affected (0.05 sec)

? mysql >select * from t3;

                +----+------+-----+
                | id | name | age |
                +----+------+-----+
                |  1 | xxx  |  10 |
                +----+------+-----+

? 列类型（*******************************************************）

? create table 表名（

? 字段名列类型 unsigned[可选的参数]，##### 记得逗号

? 字段名列类型 [可选的参数], ###记得加逗号

? 字段名列类型 [可选的参数] ####最后一行不加逗号）charset=utf8;

? 数字

? 整型

? tinyint

? smallint

? int (*********************************************************************) 推荐使用

? mediumint

? bigint

? a 整数类型

? b 取值范围

? c unsigned 加上代表不能取负数，只适用于整数

? 应用场景：
? 根据公司业务的场景，来选取合适的类型

? 浮点型（**********************************************************）

? create table t5(

? id int auto_increment primary key,

? salary decimal(16,10),

? num float) charset=utf8;

? float: 不一定精确

? decimal：非常精确地数字（500.23）decimal（6,2）m是数字总个数（负号不算），d是小数点后个数。

? 正好10位：

? mysql>:insert into t5(salary,num) values (500023.2312345678, 5000.2374837284783274832);

? Query OK, 1 row affected (0.04 sec)

? mysql>:select * from t5;

            +----+-------------------+---------+
            | id | salary            | num     |
            +----+-------------------+---------+
            |  1 | 500023.2312345678 | 5000.24 |
            +----+-------------------+---------+
            1 row in set (0.00 sec)

? 少于10位：
? mysql>: insert into t5(aslary,num) values(500023.231234567, 5000.2374837284783274832);

? Query OK, 1 row affected (0.04 sec)

? mysql>:select * from t5;

            +----+-------------------+---------+
            | id | salary            | num     |
            +----+-------------------+---------+
            |  1 | 500023.2312345678 | 5000.24 |
            |  2 | 500023.2312345670 | 5000.24 |
            +----+-------------------+---------+
        多于10位：
                mysql> insert into t5 (salary, num) values (500023.23123456789,                         5000.2374837284783274832);
                Query OK, 1 row affected, 1 warning (0.03 sec)

                mysql> select * from t5;
                +----+-------------------+---------+
                | id | salary            | num     |
                +----+-------------------+---------+
                |  1 | 500023.2312345678 | 5000.24 |
                |  2 | 500023.2312345670 | 5000.24 |
                |  3 | 500023.2312345679 | 5000.24 |
                +----+-------------------+---------+

? 字符串

? char(长度)：定长

? create table t6(

? id int unsigned auto_increment primary key,

? name char(10) not null default ‘xxxx‘)charset=utf8;

? varchar(长度)：变长

? create table t6 (

? id int auto_increment primary key,

? name varchar(10) not null default ‘xxx‘)charset=utf8;

? mysql>:insert into t6(name) values (‘hello‘);

? Query OK, 1 row affected (0.03 sec)

? mysql>:slect * from t6;

            +----+-------+
            | id | name  |
            +----+-------+
            |  1 | hello |
            +----+-------+

? 1 row in set (0.00 sec)

? mysql>insert into t6 (name) values (‘hedsudsjdksdsdsdujudjsjd‘);

? ERROR 1406 (22001): Data too long for column ‘name‘ at row 1

? 区别：
? char:定长，无论插入的字符是多少个，永远固定占规定的长度

? 场景：

? 1 身份证

? 2 手机号 char(11)

? 3 md5加密后之后的值，比如密码等 char(32)

? varchar: 变长，根据插入的字符串的长度来计算所占的字节数，但是有一个字节是用来保存字符串的大小。

? 注意：如果，不能确定插入数据的大小，一般建议使用 varchar(255)

? 时间日期类型

                    YEAR
                YYYY（1901/2155）

                DATE
                    YYYY-MM-DD（1000-01-01/9999-12-31）

                TIME
                    HH:MM:SS（'-838:59:59'/'838:59:59'）

                DATETIME  (***************************)

                    YYYY-MM-DD HH:MM:SS（1000-01-01 00:00:00/9999-12-31 23:59:59    Y）

                TIMESTAMP

                    YYYYMMDD HHMMSS（1970-01-01 00:00:00/2037 年某时）   

                例子：
                    create table t8（d date,t time,dt  datetime);

                    mysql>:insert into t8  values(now(),now(),now());

                    Query OK, 1 row affected, 1 warning (0.08 sec)

                    mysql> select * from t8;
                    +------------+----------+---------------------+
                    | d          | t        | dt                  |
                    +------------+----------+---------------------+
                    | 2019-10-29 | 10:49:51 | 2019-10-29 10:49:51 |
                    +------------+----------+---------------------+
                    1 row in set (0.00 sec)
                    insert into t8 values(now(),now(),now());

? 枚举

? 列出所有的选项

? create table t9(

? id int auto_increment primary key,

? gender enum(‘male‘,‘female‘)

? )charset = utf8;

? mysql>:insert into t9 (gender) values(‘male‘);

? Query OK, 1 row affected (0.04 sec)

? mysql>:insert into t9(gender) values(‘female‘);

? Query OK, 1 row affected (0.03 sec)

? mysql>:insert into t9(gender) values(‘sgcdtcdsgdcsd‘)

改

? 1 修改姓名

? alter table 旧表名 rename 新表明

? mysql> alter table t8 rename t88;

? Query OK, 0 rows affected (0.19 sec)

? 2 增加字段

? alter table 表名 add 字段名列类型 [可选的参数]，add 字段名列类型 [可选的参数];

? mysql>:alter table t88 add nmae varchar(32) not null default ‘ ‘;

        Query OK, 0 rows affected (0.82 sec)
        Records: 0  Duplicates: 0  Warnings: 0

? 上面添加的列永远是添加在最后一列之后

        ALTER TABLE 表名
        ADD 字段名 列类型 [可选的参数] FIRST;

        mysql> alter table t88 add name3 varchar(32) not null default '' first;
        Query OK, 0 rows affected (0.83 sec)
        Records: 0  Duplicates: 0  Warnings: 0
        alter  table  表名
        add  字段名  列类型 [可选的参数] after  字段名;

        mysql>:alter table t88 add name4 varchar(32) not null default '' after id;

        Query OK, 0 rows affected (0.68 sec)
        Records: 0  Duplicates: 0  Warnings: 0

     3 删除字段
        alter table 表名 modify 字段名 数据类型 [完整性约束条件];

        mysql>alter table t88 modify name2 char(20);
        Query OK, 1 row affected (0.88 sec)
        Records: 1  Duplicates: 0  Warnings: 0

    4修改字段

        alter table 表名 change 旧字段名 新字段名 新数据类型 [完整性约束条件];

        mysql>alter table t88 change name2 name22 varchar(32) not null default'';
        Query OK, 1 row affected (0.82 sec)
        Records: 1  Duplicates: 0  Warnings: 0

        mysql>alter table t88 change name22 name23;
        ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1

删

        drop table 表名；#### 线上禁用
        mysql>drop table t9;
        Query OK, 0 rows affected (0.18 sec)

查

        mysql>show table;
        +----------------+
        | Tables_in_test |
        +----------------+
        | t1             |
        +----------------+
        1 row in set (0.00 sec)

    复制表结构：
        mysql> ##1 查看t88表的创建语句
        mysql>show create table t88;
        +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
        | Table | Create Table                                                                                                                                                                                                                                                              |
        +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
        | t88   | CREATE TABLE `t88` (
          `name3` varchar(32) NOT NULL DEFAULT '',
          `d` date DEFAULT NULL,
          `t` time DEFAULT NULL,
          `dt` datetime DEFAULT NULL,
          `name` varchar(32) NOT NULL DEFAULT '',
          `name22` varchar(32) NOT NULL DEFAULT ''
        ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
        +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
        1 row in set (0.01 sec)

        mysql> ## 2. like
        mysql> create table t89 like t88;
        Query OK, 0 rows affected (0.33 sec)

二操作数据行

增

    

        增加数据
            语法：
                insert into 表名（列1，列2）values（值1，‘值2’）;
            例子：
                insert into t1(id,name) values(1,'tank');
                insert into t1(id,name) values(1,'tank2');
                insert into t1(id,name) values(1,'tank3');

? mysql>insert into t66(name) select name from t6;
? Query OK, 4 rows affected (0.09 sec)
? Records: 4 Duplicates: 0 Warnings: 0

删

        delete from 表名 where 条件：
            mysq>delect from t5 where id=1;
            mysql>delect from t5 where id>1;
            mysql>delect from t5 where id>=1;
            mysql>delect from t5 where id<=1;
            mysql>delect from t5 wher id<1;
            mysql>delect from t5 wher id>=1 and id<10;
            Query OK, 1 row affected (0.06 sec)

            delect from 表名;删除表中所有的数据

            mysql>insert into t5(salary,num) values(500023.2312345679,  5000.24);
            Query OK, 1 row affected (0.08 sec

            mysql>select * from t5;
            +----+-------------------+---------+
            | id | salary            | num     |
            +----+-------------------+---------+
            |  4 | 500023.2312345679 | 5000.24 |
            +----+-------------------+---------+
            1 row in set (0.00 sec)

        truncate 表名;###没有where条件的
            mysql>truncate t5;
            Query OK, 0 rows affected (0.25 sec)

            mysql>select * from t5;
            Empty set (0.00 sec)

            mysql>insert into t5(salary,num) values(500023.2312345679,  5000.24);
            Query OK, 1 row affected (0.06 sec)

            mysql>select * from t5;
            +----+-------------------+---------+
            | id | salary            | num     |
            +----+-------------------+---------+
            |  1 | 500023.2312345679 | 5000.24 |
            +----+-------------------+---------+
            1 row in set (0.00 sec)

        区别：
            1 delect之后，插入数据从上一次主键自增加1开始，truncate则是从1开始
            2delect删除，是一行一行的删除，truncate：全选删除，truancy删除的速度是高于delect的

改

?
?
? undate 表名 set 列名1=新值1，列名2=新值2，where 条件;
? mysql>update t66 set name=‘xxx‘ where id<30;
? Query OK, 1 row affected (0.04 sec)
? Rows matched: 1 Changed: 1 Warnings: 0

?
? mysql>update t66 set name=‘xxx‘ where id<30;
? mysql>update t66 set name=‘xxx‘ where id<=30;
? mysql>update t66 set name=‘xxx‘ where id>=30;
? mysql>update t66 set name=‘xxx‘ where id>30;
? mysql>update t66 set name=‘xxx‘ where id>20 and id<32;
? mysql>update t66 set name=‘xxx‘where id>20 or name=‘tank‘;

? Query OK, 1 row affected (0.04 sec)
? Rows matched: 1 Changed: 1 Warnings: 0

查

?
?
? 语法：
? select 列1，列2 from 表名;(代表查询所有列)
? select from t66 where id>30 and id<40;
? select * from t66 where id>30;
? select * from t66 where id<30;
? select * from t66 where id<=30;
? select * from t66 where id>=30;
? select * from t66 where id!=30;
? select * from t66 where id<>30;
? mysql>select * from from t1;
? +------+-------+
? | id | name |
? +------+-------+
? | 1 | zekai |
? +------+-------+
? 1 row in set (0.00 sec)
?

                between...and....取值范围是闭区间

?
? select * from where id between 30 and 40；
? mysql>select * from t66 where id between 31 and 33;
? +----+--------+
? | id | name |
? +----+--------+
? | 31 | dsadsa |
? | 32 | dsadsa |
? | 33 | dsadsa |
? +----+--------+
? 避免重复distinct

? mysql>select distinct name from t66;

                +--------+
                | name   |
                +--------+
                | xxxx   |
                | hds    |
                | dsadsa |
                +--------+
                3 rows in set (0.00 sec)
                通过四则运算查询 （不要用）
                mysql> select name, age*10 from t3;
                +------+--------+
                | name | age*10 |
                +------+--------+
                | xxx  |    100 |
                +------+--------+
                1 row in set (0.01 sec)

                mysql> select name, age*10 as age from t3;
                +------+-----+
                | name | age |
                +------+-----+
                | xxx  | 100 |
                +------+-----+
                1 row in set (0.02 sec)

                in(80,90,100):
                mysql> select * from t66 where id in (23,34,11);
                +----+------+
                | id | name |
                +----+------+
                | 11 | xxxx |
                | 23 | hds  |
                +----+------+
                2 rows in set (0.04 sec)

                like:模糊查询
                    以x开头：
                        mysql>select * from t66 where name like 'x%';
                            +----+------+
                            | id | name |
                            +----+------+
                            |  1 | xxxx |
                            |  2 | xxxx |
                            |  3 | xxxx |
                            |  4 | xxxx |
                            |  8 | xxxx |
                            |  9 | xxxx |
                            | 10 | xxxx |
                            | 11 | xxxx |
                            | 15 | xxxx |
                            | 16 | xxxx |
                            | 17 | xxxx |
                            | 18 | xxxx |
                            | 30 | xxxx |
                            +----+------+
                            13 rows in set (0.05 sec)

?
? 以x结尾：
? mysql>select * from t66 where name like ‘%x‘;
?

                                +----+------+
                                | id | name |
                                +----+------+
                                |  1 | xxxx |
                                |  2 | xxxx |
                                |  3 | xxxx |
                                |  4 | xxxx |
                                |  8 | xxxx |
                                |  9 | xxxx |
                                | 10 | xxxx |
                                | 11 | xxxx |
                                | 15 | xxxx |
                                | 16 | xxxx |
                                | 17 | xxxx |
                                | 18 | xxxx |
                                | 30 | xxxx |
                                +----+------+
                                13 rows in set (0.00 sec)

?
? 包含x的：
? mysql>select * from t66 where name like ‘%x%;
?

                            不让用

作业

    1. 查看岗位是teacher的员工姓名、年龄
    select name,age from staff_info where jobs = 'teacher';
  2. 查看岗位是teacher且年龄大于30岁的员工姓名、年龄
     select name,age from staff_info where jobs = 'teacher' and age > 30;
  3. 查看岗位是teacher且薪资在9000-1000范围内的员工姓名、年龄、薪资
     select name,age,salary from staff_info where jobs = 'teacher' and salary between 9000 and 10000;
  4. 查看岗位描述不为NULL的员工信息
     select * from staff_info where jobs_info is not null;
  5. 查看岗位是teacher且薪资是10000或9000或30000的员工姓名、年龄、薪资
     select name,age,salary from staff_info where jobs = 'teacher' and salary in(10000,9000,30000);
  6. 查看岗位是teacher且薪资不是10000或9000或30000的员工姓名、年龄、薪资
     select name,age,salary from staff_info where jobs = 'teacher' and salary not in(10000,9000,3000);
  7. 查看岗位是teacher且名字是jin开头的员工姓名、年薪
     select name,salary from staff_info where jobs = 'teacher' and name like jin%;

原文地址：https://www.cnblogs.com/1012zlb/p/11762256.html

时间： 2024-10-17 00:26:48

数据库表操作与列操作

一操作表

增

改

删

查

二操作数据行

增

删

改

查

作业