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表中行操作
1、select--查询
1.1、查询某一列
select 列名 from 表名
select name from table_city
1.2、查询所有
select * from 表名
2、insert--插入
2.1、默认插入选项
insert into 表名 values (值1, 值2)
insert into table_city values (1, 'sun')
2.2、插入时设置指定列值
insert into 表名 (列1, 列2) values (值1, 值2)
insert into table_city (id, name) values (1, 'sun')
3、where -- 条件选取
select 列名 from 表名 where 条件列 运算符 值
select name from table_city where city='beijing'
4、update -- 更新表
update 表名 set 列1 = 新值, 列2 = 新值
update table_city set name = 'shanghai'
update table_city set name = 'shanghai' where id > 4
5、delete -- 删除表中行
delete from 表名 where 条件列名 = 值
delete from table_city from name = 'shanghai'
6、and -- 多条件满足过滤
select * from 表名 where 条件列1 = 值 and 条件列2 = 值
select * from table_city where name = 'beijing' and age = 22
7、 or -- 条件之一满足过滤
select * from 表名 where 条件列1 = 值 or 条件列2 = 值
select * from table_city where name = 'beijing' or age = 22
8、order by -- 表排序
select 列名 from 表名 order by 条件列1, 条件列2
asc -- 升序 -- 默认
select name from table_city order by age, name
desc -- 降序
select name from table_city order by age desc
name升序, age降序
select name from table_city order by age desc, name asc
9、group by -- 结果集分组,结合合计函数 sum()
O_Id | OrderDate | OrderPrice | Customer |
---|---|---|---|
1 | 2008/12/29 | 1000 | Bush |
2 | 2008/11/23 | 1600 | Carter |
3 | 2008/10/05 | 700 | Bush |
4 | 2008/09/28 | 300 | Bush |
5 | 2008/08/06 | 2000 | Adams |
6 | 2008/07/21 | 100 | Carter |
select Customer,sum(OrderPrice) from Orders group by Customer
Customer | SUM(OrderPrice) |
---|---|
Bush | 2000 |
Carter | 1700 |
Adams | 2000 |
将相同的Customer 列,通过合计函数计算总和,去除重复项,返回新的结果集,忽略group by 如下情况:
Customer | SUM(OrderPrice) |
---|---|
Bush | 5700 |
Carter | 5700 |
Bush | 5700 |
Bush | 5700 |
Adams | 5700 |
Carter | 5700 |