基础sql语句

Posted 2020-08-09 小天_y

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// 创建数据库
create database databaseName;
e.g:create database sample;
// 显示数据库状态
status;
// 使用数据库
use databaseName;
// 删除整个数据库
drop database databaseName;

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// 创建数据库表
create table tableName(cols);
e.g: create table students
（
id int unsigned not null auto_increment primary key,
name char(8) not null,
sex char(4) not null,
age tinyint unsigned not null,
tel char(13) null default "-"
);
// 重命名表
alter table tableName rename new_tableName;
e.g:alter table students rename workmates;
// 删除表
drop table tableName;
// 删除表中的数据
delete from tableName where [condition];
e.g:delete from students where id=2;
// 显示表
show tables;
// 显示表结构
describe tableName;
e.g:describe students;

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// 插入表数据
insert into tableName values(cols);
e.g: insert into students values(NULL, "王刚", "男", 20, "13811371377");
// 查询表数据
select colName1, colName2 from tableName where [conditions];
e.g: select name, age from students where age>18;
// 更新表数据
update tableName set colName=new_value where [condition];
e.g:update students set age=23 where id=2;
// 修改表结构
// 添加列
alter table tableName add colName col_dataType [after colName];
e.g:alter table students add birthday date after age;
e.g:alter table students add address char(60);
// 修改列
alter table tableName change colName new_colName col_dataType;
e.g:alter table students change name name char(16) not null;
// 删除列
alter table tableName drop colName;
e.g:alter table students drop birthday;

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// 日期操作：date_add和date_sub.
mysql> select * from students;
+----+--------+-----+-----+------------+-------------+--------------+
| id | name | sex | age | birthday | tel | address |
+----+--------+-----+-----+------------+-------------+--------------+
| 1 | 杨家将 | 男 | 26 | 2016-07-28 | 12345678901 | 喝粥大学 |
| 2 | 刘姥姥 | 女 | 25 | 2016-06-03 | 12121212121 | 吃饭大学 |
+----+--------+-----+-----+------------+-------------+--------------+
// 查询以当前时间为原点，以birthday为查询标的，向前向后延伸150days的所有记录.
select name from students where date_sub(now(), interval 150 day) <=birthday;
// 查询以2016-07-01为原点，以birthday为查询标的，向前向后延伸20days的所有记录.
select name from students where date_sub(‘2016-07-01‘, interval 20 day) <=birthday;
// 以2016-07-23为原点，以birthday为查询标的，向前向后延伸30days的所有记录Records, 查询不在Records记录中的其他记录.
select name from students where date_sub(‘2016-07-01‘, interval 30 day) >birthday;
// 以2016-06-01增加30days所得到的时间点为OriginDay，查询在OriginDay时间之后的所有记录.
select name from students where date_add(‘2016-06-01‘, interval 30 day) <=birthday;
// 以2016-06-01增加30days所得到的时间点为OriginDay，查询在OriginDay时间之前的所有记录.
select name from students where date_add(‘2016-06-01‘, interval 30 day) > birthday;
// 查询两个日期之间的记录.
select * from students where birthday between ‘2016-06-11‘ and ‘2016-07-29‘;
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