Multi-Table connection in the database

1. External Connection

select   *   from  T_N  left  join  T_S  on   T_N.id=T_S.id 

 

select   *   from  T_N  right  join  T_S  on   T_N.id=T_S.id 

select * from T_N full join T_S on T_N.id=T_S.id 

2. Internal Connection

select   *   from   T_N   join   T_S   on   T_N.id=T_S.id 

3. Cross join

select   *   from   T_N  cross  join   T_S  

Conclusion

// View of the total number of recharged and consumed items with external connections established

SELECT Recharge_Info.CardID, Line_info.cardID AS LcardID, SUM(Recharge_Info.AddMoney) AS sumAddMoney, SUM(Line_info.consume) AS sumConsumeFROM  Line_info RIGHT OUTER JOIN  Recharge_Info ON Line_info.cardID = Recharge_Info.CardIDGROUP BY Recharge_Info.CardID, Line_info.cardID