MySql(翌日)

文書ディレクトリ

データベース照会操作

1.単一テーブルクエリ

.マルチテーブルクエリ

3.MySqlリモート接続

データベース・クエリー・アクション
1.単一テーブルクエリ

--         
--      
-- create database python_test_1 charset=utf8;

--      
-- use python_test_1;

-- students 
-- create table students(
--     id int unsigned primary key auto_increment not null,
--     name varchar(20) default '',
--     age tinyint unsigned default 0,
--     height decimal(5,2),
--     gender enum(' ',' ','  ','  ') default '  ',
--     cls_id int unsigned default 0,
--     is_delete bit default 0
-- );

-- classes 
-- create table classes (
--     id int unsigned auto_increment primary key not null,
--     name varchar(30) not null
-- );


--     
	--       
	-- select * from   ;
select * from students;

	--       
	-- select  1, 2,... from   ;
select name,age from students;
	
	--    as       
	-- select    as   .... from   ;
select name as name2 from students;
	

	-- select   .   .... from   ;
	select students.name from students;
	
	
	--      as      
	-- select   .   .... from    as   ;

	select name from students as s;

	select s.name from students as s;
	
	
	

	--      (   )
	
	-- distinct    
select distinct gender from students;
	

--     
	--      
		> >= < <= != = <>
		-- select .... from    where .....
		-- >
		--       18    

		select * from students where age > 18;


		-- <
		--       18    

		select * from students where age < 18;
		
		

		-- >=
		-- <=
		--         18    
		select * from students where age <= 18;

		-- =
		--      18         
		select * from students where age = 18;



		-- !=    <>
		--       18         
		
		select * from students where age != 18;

		select * from students where age <> 18;
		
		

	--      
	and or not
		-- and
		-- 18 28         

		select * from students where age > 18 and age < 28;


		-- 18      

		select * from students where age > 18 and gender = ' ';


		-- or
		-- 18        180(  )  

		select * from students where age > 18 or height >= 180;
		

		-- not
		--    18               
		-- select * from students where not (age>18 and gender=2);
		
		select * from students where not ( age > 18 and gender = ' ');

		select * from students not age > 18 and gender = ' ';



	--     (where name like       )
		-- like 
		-- %      
		-- _   1 
		--         " "      

		select * from students where name like ' %';
		

		--         " "      
		select * from students where name like '% %';
		

		--    2     
		select * from students where name like '__';
		


		--    3     
		select * from students where name like '___';
												
		

		--      2     
		select * from students where name like '__%';
		


	--     
		-- in (1, 3, 8)            
		--       18 34   

		select name from students where age = 18 or age = 34 or age = 56;

		select * from students where age in (18,34,56);
		

		-- not in          
		--      18 34    

		select * from students where age not in (18,34,56);

		
		-- between ... and ...           
		--       18 34      
		--         ,           
		select * from students where age between 18 and 34;
		

		
		-- not between ... and ...            
		--        18 34      
			select * from students where age not between 18 and 34;
		


	--    
		--   is null
		--          
		select * from students where  height is null;


		--    is not null

		select * from students where height is not null;
		


--   
	-- order by   
	-- asc
	-- asc      ，   
	-- desc
	-- desc      ，   
	--      18 34      ，           

	select * from students where age between 18 and 34 
	and gender = ' ' order by age asc ;

	


	--      18 34      ，        

select * from students where age >= 18 and age <= 34 and gender=' '
 order by height desc;
	

	-- order by     
	--      18 34      ，        , 
	--                     
select * from students where age >= 18 and age <= 34 and gender=' '
 order by height desc , age asc;
	
    --            id      
select * from students where age >= 18 and age <= 34 and gender=' '
 order by height desc , age asc, id desc;

--       ,         
	
	


--     
	--   
	-- count
	--         
	select count(*) from students where gender = ' '; 

	
	--    
	-- max
	--        
	select max(age) from students;
	
	--           
	select max(height) from students where gender = ' ';


	--    
	-- min
	select min(height) from  students where gender = ' ';



	--   
	-- sum
	--           
	
	select sum(age) from students;
	
	--    
	-- avg
	--       
	select avg(age) from students;
	


	--        sum(age)/count(*)
select sum(age)/count(*) from students;

	


	--      round(123.23 , 1)   1   
	--           ，  2   

	select round( avg(age),2) from students ;
	


	--             2   

	select avg(height) from students;

	select sum(height) / count(*) from students;

	select count(height)  from students;

	-- sql null       
select sum(height) / count(height) from students;

	


--   

	      
	select      from    group by      ;

	-- group by
	--       ,       

	select gender from students group by gender;



	--           

	select gender,count(*) from students group by gender;



	-- group_concat(...)
	--           

	select gender,group_concat(name) from students group by 
	gender;

	


	
	--            
	select gender,avg(age) from students group by gender;
	


	-- having(  having group by    having           )
	--         30    ，    

	select gender,avg(age),group_concat(name) from students group by gender
	 having avg(age) > 30;
	

	
	--             2    

	select gender,count(*) from students group by gender
	 having count(*) > 2;

	



	-- with rollup      (  )
	select gender,count(*) from students group by gender
	 with rollup having count(*) > 2;
    



--   
	-- limit start, count
	-- limit      (  )

	     : (  -1)*     
	
	--            
	--    5   
	select * from students limit 0,5; 



	--     2 ， 1   
	select * from students limit 0,2;
	

	--     2 ， 2   
	select * from students limit 2,2;

	--     2 ， 3   
	select * from students limit 4,2;

	--     2 ， 4   

	select * from students limit 6,2;


	

	--     2 ，   6    ,           
	select  * from students order by age asc limit 10,2;

	--       ,         

2.マルチテーブルクエリ

--     
	-- inner join ... on
	-- select ... from  A inner join  B;
	--                    
	select * from students inner join classes 
	 on students.cls_id = classes.id;


	--         、  

	select students.name,classes.name from students inner join classes 
		on students.cls_id = classes.id;


	--        

	select s.name,c.name from students as s
	 inner join classes as c
		on s.cls_id = c.id;



	--                    ，          students.*，        classes.name.

	select students.*,classes.name from students inner join classes
	 on students.cls_id = classes.id;
	--        ，        1 

select classes.name, students.* from students inner join classes
	 on students.cls_id = classes.id;
	--                    ,          
	
select classes.name, students.* from students inner join classes
	 on students.cls_id = classes.id order by classes.name asc;
	
	
	--           ，     id        
select classes.name, students.* from students inner join classes
	 on students.cls_id = classes.id order by classes.name asc ,
	 students.id asc;
		



	-- left join
	--              

	--  ,                      

	select * from students left join classes 
	on students.cls_id = classes.id;


	


	--              

select * from students left join classes 
	on students.cls_id = classes.id where classes.id is null;
	
	-- right join   on
	--           ， left join  

	select * from students right join classes 
	on classes.id = students.cls_id;



	

--    
	--      :              (    )
	--     :         (    )
	--     :         (    )
	
	--             (height)
	select avg(height) from students;

	select * from students where height > 172.076923;

	select * from students where height >
	 (select avg(height) from students);



	--                   

	select id from classes;

	select * from students where cls_id in(1,2);

	select * from students where cls_id in (select id from classes);

	
	--        
	--      
	create table areas(
    aid int primary key,
    atitle varchar(20),
    pid int
	);
	-- sql       
	-- source     /areas.sql;
	--            ,      ,      
source xxx/areas.sql;
	
	--         
	select * from areas where pid is null;

	-- 1：       “   ”     

	select aid from areas where atitle = '   ';
	select * from areas where pid = 
	(select aid from areas where atitle = '   ');


	select * from areas as a1 inner join areas as a2
	 on a1.pid = a2.aid where a2.atitle = '   ';



	-- 2：       “   ”     
select * from areas where pid = 
	(select aid from areas where atitle = '   ');

	select * from areas as a1 inner join areas as a2
	 on a1.pid = a2.aid where a2.atitle = '   ';

3.MySqlリモート接続