oracle裏表連接支持標準寫法,但也有oracle特殊的寫法,這兩種寫法在某些場景下會有差異,推薦使用標準寫法,這裏只是介紹表連接標準語法及瞭解oracle的特殊寫法。
標準連接語法:
select table1.column , table2.column
from table1
[corss join table2]
[national jon table2]
[join table2 using (column)]
[join table2 on (table1.column=table2.column)]
[left | right | full outer join table2 on (table1.column=table2.column)];
實際使用中on關鍵字後的連接字段不用括號也可以正常使用。
多表連接:
--先連接table4和table5並將其結果集命名爲table2,再與table1連接 select table1.column,table2.column from table1 inner join ( select table4.column,table5.column from table4 inner join table5 on table4.column =table5.column ) as table2 on table1.column=table2.column; 等同於 select table1.column ,table2.column from table1 ,(select table4.column,table5.column from table4,table5 where table4.column=table5.column) as table2 where table1.column=table2.column; --連接table1,table2,table3,沒有連接順序之分 select table1.column,table2.column,table3.column from table1 inner join table2 on table1.column=table2.column inner join table3 on table1.column=table3.column; 等同於 select table1.column,table2.column,table3.column from table1,table2.table3 where table1.column=table2.column and table1.column=table3.column;
內連接:
標準寫法:
select table.column , table2.column from table1 inner join table2 on (table1.column=table2.column);
oracle 特殊寫法:
select table.column , table2.column from table1 ,table2 where table1.column=table2.column;
左連接:
標準寫法:
select table.column , table2.column from table1 left join table2 on (table1.column=table2.column);
oracle 特殊寫法:
select table.column , table2.column from table1 ,table2 where table1.column=table2.column(+);
右連接:
標準寫法:
select table.column , table2.column from table1 right join table2 on (table1.column=table2.column);
oracle 特殊寫法:
select table.column , table2.column from table1 ,table2 where table1.column(+)=table2.column;
全連接:
標準寫法:
select table.column , table2.column from table1 full join table2 on (table1.column=table2.column);
oracle 特殊寫法:
select table.column , table2.column from table1 ,table2 where table1.column(+)=table2.column(+);