[mysql] join, union

There are two sample tables.

 

select * from info;
select * from info1;

 

join

select * from info 
join info1
on info.ID = info1.no;

the join is to make the same condition both tables based on ID

 

 

select * from info 
left join info1
on info.ID = info1.no;

The left join is the second table will be into the first table.

 

union

select cc.code
from info1 as cc
union all
select dd.code
from info as dd;

'union all' includes all values. 'union' ignores the same values.

 

 

the number of columns should be same.

select ID, Ecode , day_time
from info
union all
select *
from info1;