1. 查询：select column from table where condition group by column having condition order by column limit start,end
a) 去掉重复：select disdinct column from table
b) 条件：select column from table where condition（非空column is not null）
c) 多个条件：select column from table where condition1 and condition2
d) 离散值集：select column from table where column in (value1,value2)
e) 连续值域：select column from table where column between from and to
f) 相似值：select column from table where column like ‘%key%’
g) 排序：select column from table order by column desc
h) 函数：select sum|count|avg|max|min(column) from table
i) 分组：select column from table group by column
j) 函数结果限定：select sum(col) from table group by col having sum(col) > 1
k) 别名：select sum(column) as alias from table
l) 连接：select a1.col1,a2.col2 from table1 as a1,table2 as a2 where al.col = a2.col
左（右）连接：select column from table1 left|right join table2 on table1.col = table2.col
m) 外连接：不要求两个表都有同一笔数据，where a1.col = a2.col(+)
全连接：select column from table1 full join table2
n) 子查询：select col from table where name in (select name from table where condition)
o) 合并：select col from table1 union select col from table2，disdict唯一，union all全部
p) 交集：select-statement intersect select-statement
q) 差集：select-statement minus select-statement
r) 拼接字段：select concat(column1,column2) from table
s) 裁剪字段：select substr(column,pos[,len]) from table，pos从1开始，len太长会出错
t) 去掉空白：select [l|r]trim(column) from table，直接用select trim(“ haha ”)
2. 创建：
a) 表：
create table table_name
(First_Name char(50),
Last_Name varchar(50),
Birth_Date date)
b) 视图：虚拟表格，在实际表格基础之上，创建视图后查看用select * from view_name
create view view_name as
select-statement
c) 索引：命名可考虑idx、table、column相关，创建时添加key idx_name (column)
create index index_name on table(column)
3. 重构：
a) 添加列：alter table add column type
b) 改列名：alter table change old_column new_column type
c) 改类型：alter table modify column type
d) 删除列：alter table drop column
e) 主键：alter table add primary key (column)，创建时添加primary key (column)
f) 外键：alter table add foreign key (column) references table(column)，创建时添加foreign key (column) references table(column)
g) 删除表：drop table table_name
h) 清空表（保留表结构）：truncate table table_name
4. 更新：
a) 添加行：insert into table(column) values(value)
b) 添加查询结果：insert into table(column) select-statement
c) 更改行：update table set column = value where condition
d) 删除行：delete from table where condition