oracle 外联接

oracle 外联接 “(+)” 的用法：

Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 Connected as scottSQL> select deptno from dept; DEPTNO------    10    20    30    40    50 SQL> select ename from emp; ENAME----------SMITHALLENWARDJONESMARTINBLAKECLARKSCOTTKINGTURNERADAMSJAMESFORDMILLER 14 rows selected SQL> select d.deptno,e.ename from dept d,emp e where e.deptno(+)=d.deptno; DEPTNO ENAME------ ----------    20 SMITH    30 ALLEN    30 WARD    20 JONES    30 MARTIN    30 BLAKE    10 CLARK    20 SCOTT    10 KING    30 TURNER    20 ADAMS    30 JAMES    20 FORD    10 MILLER    50     40  16 rows selected SQL> select d.deptno,e.ename from dept d,emp e where e.deptno=d.deptno(+); DEPTNO ENAME------ ----------    20 SMITH    30 ALLEN    30 WARD    20 JONES    30 MARTIN    30 BLAKE    10 CLARK    20 SCOTT    10 KING    30 TURNER    20 ADAMS    30 JAMES    20 FORD    10 MILLER 14 rows selected

?结果表示 “(+)” 出现在哪张表旁边，则那张表为补充表。