SQL Example-Join

<title>SQL Example 10–join</title> SQL Example 10–join

Inner joins inside joins

Left  [outer] Join    # outer can omit right [outer] join    # outer can omit

Create Table worker(WIDintAuto_incrementPrimary Key, fnamevarchar(20) not NULL, lnamevarchar(20) not NULL);Create Table Job(Jidint  not NULLAuto_incrementPrimary Key, job_namevarchar(20) not NULL);Insert  intoWorker (fname, lname)Values(' A ',' A '), (' B ',' B '), (' C ',' C ');Insert  intoJob (Job_name)Values(' Cleaner '), (' farmer '), (' Boss ');

• Join
  

  Select  from join Job J;

  | fname | lname | Job_name |+-------+-------+----------+| A     | a |     cleaner  | | b     | b     | cleaner  | | c     | c     | cleaner  | | A     | a     | farmer< c15/>| | b     | b |     farmer   | | c     | c     | farmer   | | A     | a     | boss     | | b     | b     | boss
       | | C |     C     | boss     |

  Select  from Join where w.wid = J.jid;

  | fname | lname | Job_name |+-------+-------+----------+| A     | a |     cleaner  | | b     | b     | farmer   | | c     | c     | boss     |

  Insert  into Values (' d'd ');

  Select  from Join where w.wid = J.jid;

  | fname | lname | Job_name |+-------+-------+----------+| A     | a |     cleaner  | | b     | b     | farmer   | | c     | c     | boss     |

• Left Join
  To be continued, occupy a position first <2015-06-14 20:57>
  
• Right Join
  To be continued, occupy a position first <2015-06-14 20:57>
  

SQL Example-Join