1、选择：select * from table1 where 范围
插入：insert into table1(field1,field2) values(value1,value2)
删除：delete from table1 where 范围
更新：update table1 set field1=value1 where 范围
查找：select * from table1 where field1 like ’%value1%’ —like的语法很精妙，查资料!
排序：select * from table1 order by field1,field2
总数：select count * as totalcount from table1
求和：select sum(field1) as sumvalue from table1
平均：select avg(field1) as avgvalue from table1
最大：select max(field1) as maxvalue from table1
最小：select min(field1) as minvalue from table1
2、说明：子查询(表名1：a 表名2：b)
select a,b,c from a where a IN (select d from b )
或者: select a,b,c from a where a IN (1,2,3)
3、说明：显示文章、提交人和最后回复时间
select a.title,a.username,b.adddate from table a,
(select max(adddate) adddate from table where table.title=a.title) b
4、说明：外连接查询(表名1：a 表名2：b)
select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c
5、说明：在线视图查询(表名1：a )
select * from (SELECT a,b,c FROM a) T where t.a 》 1;
6、说明：between的用法,between限制查询数据范围时包括了边界值,not between不包括
select * from table1 where time between time1 and time2
select a,b,c, from table1 where a not between 数值1 and 数值2
7、说明：in 的使用方法
select * from table1 where a in (‘值1’,’值2’,’值4’,’值6’)
8、说明：四表联查问题：
select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c inner join d on a.a=d.d where …..
网址1：http://haodro.com/archives/5969
网址2：https://blog.csdn.net/qq_43607201/article/details/97156350
网址3：https://blog.csdn.net/weixin_42078450/article/details/87909310?spm=1001.2101.3001.6650.6&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-6-87909310-blog-97156350.235%5Ev38%5Epc_relevant_sort&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-6-87909310-blog-97156350.235%5Ev38%5Epc_relevant_sort
