MySQL_Table_Join_Query

    1. Internal connection

    i. No connection

select * from t_book, t_bookType;

    ii. Where =

select bookName, author, bookTypeName  from t_book, t_bookType where t_book.bookTypeId = t_bookType.id;

    iii. Abbreviation

select tb.bookName, tb.author, tbt.bookTypeName  from t_book tb, t_bookType tbt where tb.bookTypeId = tbt.id;

    2. External connection

• Be careful: left join --> all information of first table

                            right join --> all information of second table

select * from t_book tb left join t_bookType tbt on tb.bookTypeId = tbt.id;
select * from t_book tb right join t_bookType tbt on tb.bookTypeId = tbt.id;

    3. Multi condition --> and

select tb.bookName, tb.author, tb.price, tbt.bookTypeName  from t_book tb, t_bookType tbt where tb.bookTypeId = tbt.id and tb.price>70;

转载于:https://my.oschina.net/u/2363350/blog/669895