《Mysql入门日常收集整理常见的mysql sql技巧》要点：
本文介绍了Mysql入门日常收集整理常见的mysql sql技巧，希望对您有用。如果有疑问，可以联系我们。
MYSQL入门废话不多说了,直接给大家贴代码了.
MYSQL入门1,数字辅助表
MYSQL入门
//创建表
create table test(id int unsigned not null primary key);
delimiter //
create procedure pnum(cnt int unsigned)
begin
declare i int unsigned default 1;
insert into num select i;
while i*2 < cnt do
insert into num select i+id from num ;
set i=i*2;
end while;
end
//
delimiter ;
#####列值不连续问题：
表a中id值为1,2,3,100,101,110,111
set @q=0;
select id,@q:=@q+1 as cn from a;
#####对不连续的进行分组
set @a=0;
select min(id) as start_v,max(id) as end_v from (
select id,cn,id-cn as diff from (
select id,@a:=@a+1 as cn from pi) as p ) as pp group by diff;
#####对不连续的值填充
use test;
DROP TABLE if EXISTS pincer;
create table pincer(a int UNSIGNED);
insert into pincer values(1),(2),(5),(100),(101),(103),(104),(105);
select a+1 as start ,(select min(a)-1 from pincer as ww where ww.a>qq.a) as end from pincer as qq where
not exists (select * from pincer as pp where qq.a+1=pp.a)
and a<(select max(a) from pincer);
################
select id,num,ranknum,diff from (select id,num,ranknum,num-ranknum as diff from (select id,num,if(@id=id,@rownum:=@rownum+1,@rownum:=1) ranknum,@id:=id from tt,(select @rownum:=0,@id:=null) a ) b) c group by id,diff having count(*)>=2;
################
MYSQL入门2,生日问题
MYSQL入门
select name,birthday,if(cur>today,cur,next) as birth_day
from(
select name,birthday,today,date_add(cur,interval if(day(birthday)=29 && day(cur)=28,1,0) day)as cur, date_ad(next,interval if(day(birthday)=29 && day(next)=28,1,0) day) as next
from(
select name,birthday,today,
date_add(birthday,interval diff year) as cur,
date_add(birthday,interval diff+1 year) as next,
from(
select concat(laster_name,'',first_name) as name,
birth_date as birthday,
(year(now())-year(birth_date) )as diff,
now() as today
from employees) as a
) as b
) as c
MYSQL入门3,日期问题----计算工作日
MYSQL入门
create table sals(id int ,date datetime ,cost int,primary key(id);
select date_add('1900-01-01',
interval floor(datediff(date,'1900-01-01')/7)*7 day)
as week_start,
date_add('1900-01-01',
interval floor(datediff(date,'1900-01-01')/7*7+6 day)
as week_end,
sum(cost) from sales;
计算工作日(指定2个日期段 有多少工作日)
create procedure pgetworkdays (s datetime,e datetime)
begin
select floor(days/7)*5+days%7
case when 6 between wd and wd+days%7-1 then 1 else 0 end
case then 7 between wd and wd+days%7-1 then 1 else 0 end
from
(select datediff(e,s)+1 as days,weekday(s)+1 as wd) as a;
end;
MYSQL入门mysql sql语句大全
MYSQL入门1、说明：创建数据库
CREATE DATABASE database-name
MYSQL入门2、说明：删除数据库
MYSQL入门drop database dbname
MYSQL入门3、说明：备份sql server
--- 创建 备份数据的 device
USE master
EXEC sp_addumpdevice 'disk', 'testBack', 'c:\mssql7backup\MyNwind_1.dat'
--- 开始 备份
BACKUP DATABASE pubs TO testBack
MYSQL入门4、说明：创建新表
MYSQL入门create table tabname(col1 type1 [not null] [primary key],col2 type2 [not null],..)
根据已有的表创建新表：
A：create table tab_new like tab_old (使用旧表创建新表)
B：create table tab_new as select col1,col2… from tab_old definition only
MYSQL入门5、说明：删除新表
MYSQL入门drop table tabname
MYSQL入门6、说明：增加一个列
Alter table tabname add column col type
注：列增加后将不能删除.DB2中列加上后数据类型也不能改变,唯一能改变的是增加varchar类型的长度.
MYSQL入门7、说明：添加主键： Alter table tabname add primary key(col)
说明：删除主键： Alter table tabname drop primary key(col)
MYSQL入门8、说明：创建索引：create [unique] index idxname on tabname(col….)
MYSQL入门删除索引：drop index idxname
MYSQL入门注：索引是不可更改的,想更改必须删除重新建.
MYSQL入门9、说明：创建视图：create view viewname as select statement
MYSQL入门删除视图：drop view viewname
MYSQL入门10、说明：几个简单的基本的sql语句
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 [desc]
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
MYSQL入门11、说明：几个高级查询运算词
A： UNION 运算符
UNION 运算符通过组合其他两个结果表(例如 TABLE1 和 TABLE2)并消去表中任何重复行而派生出一个结果表.当 ALL 随 UNION 一起使用时(即 UNION ALL),不消除重复行.两种情况下,派生表的每一行不是来自 TABLE1 就是来自 TABLE2.
B： EXCEPT 运算符
EXCEPT 运算符通过包括所有在 TABLE1 中但不在 TABLE2 中的行并消除所有重复行而派生出一个结果表.当 ALL 随 EXCEPT 一起使用时 (EXCEPT ALL),不消除重复行.
C： INTERSECT 运算符
INTERSECT 运算符通过只包括 TABLE1 和 TABLE2 中都有的行并消除所有重复行而派生出一个结果表.当 ALL 随 INTERSECT 一起使用时 (INTERSECT ALL),不消除重复行.
注：使用运算词的几个查询结果行必须是一致的.
MYSQL入门12、说明：使用外连接
MYSQL入门A、left (outer) join：
左外连接(左连接)：结果集几包括连接表的匹配行,也包括左连接表的所有行.
SQL: select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c
B：right (outer) join:
右外连接(右连接)：结果集既包括连接表的匹配连接行,也包括右连接表的所有行.
C：full/cross (outer) join：
全外连接：不仅包括符号连接表的匹配行,还包括两个连接表中的所有记录.
12、分组:Group by:
一张表,一旦分组完成后,查询后只能得到组相关的信息.
组相关的信息：(统计信息) count,sum,max,min,avg 分组的标准)
在SQLServer中分组时：不能以text,ntext,image类型的字段作为分组依据
在selecte统计函数中的字段,不能和普通的字段放在一起；
MYSQL入门13、对数据库进行操作：
MYSQL入门分离数据库： sp_detach_db; 附加数据库：sp_attach_db 后接表明,附加需要完整的路径名
MYSQL入门14.如何修改数据库的名称:
MYSQL入门sp_renamedb 'old_name', 'new_name'
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