### MySQL 


##### 

 1. #####  ( sql  sql )

    + 

      ```mysql
      select * 
      from tab_name 
      where  
      in (
          select  
          from tab_name
      );
      ```

    + 
    + 

	2. #####  (, , where , and )

    + 

      ```mysql
      select * 
      from tab_name1, tab_name2
      where
      ;
      ```

	3. ##### 

    	1.  (inner join , inner )

        + 

          ```mysql
          select * 
          from tab_name1 inner join tab_name2 
          on  
          where ;
          ```

        +  where. 

          

    2. 

       + 

         ```mysql
         select *
         from left_tab_name left join right_tab_name 
         on 
         where ;
         ```

       + ,,,null.

    3. 

       + 

         ```mysql
         select *
         from left_tab_name right join right_tab_name
         on 
         where ;
         ```

       + ,,,,null

#### 

 1. #####  ******      ,,,,,,. (,)

 2. ##### 

    +  :   ,    ,     
    + InnoDB 
      + mysql 5.5 , **** 
      +  : 
    + MyISAM 
      +  ****
      + 

3. #####  (ACID)

   +  (Atomicity)
     + ,,,
   +  (Consistency)
     + ,
   +  (Isolation)
     + ,,
   +  (Durability)
     + ,,

4. #####  ()

   1.  (Dirty Read)
      + A   B ****, , B ,  A 
   2.  (Unrepeatable Read)
      + , A ****,B****, A 
   3.  (Phantom Read)
      +  A, B , A ****, B ****, A 

5. #####  (,)

   1. Read Uncommitted ( )
      + . 
      + , ****, ,
      + 
   2. Read committed ( )
      + 
      + ,,,
      + ,
   3. Repeatable read ( )
      + 
      +  () , , 
      + 
   4. Serializable ()
      + 
      + ,,

6. ##### 

   1.  (,)

      ```mysql
      set session transaction isolation level ;
      ```

   2. 

      ```mysql
      begin;
      ```

   3. 

      ```mysql
      commit;
      ```

   4. 

      ```mysql
      rollback;
      ```