Oracle中SQL Server APPLY的等价物是什么？

Question

我是Oracle的新手.是否有一个builtin关键字执行SQL Server APPLY相同的工作？

Answer 1

我认为在Oracle中等效的APPLY子句称为横向JOIN.Oracle中的横向连接是当您使用函数F连接表A时输出行,并且此函数具有A列作为参数.

让我们用这个设置构建一个小例子:

SQL> CREATE OR REPLACE TYPE emp_row AS OBJECT (
  2     empno NUMBER(4),
  3     ename VARCHAR(10),
  4     job VARCHAR(9),
  5     deptno NUMBER(2)
  6  );
  7  /

Type created
SQL> CREATE OR REPLACE TYPE emp_tab AS TABLE OF emp_row;
  2  /

Type created
SQL> CREATE OR REPLACE FUNCTION get_emp_dept(p_deptno NUMBER) RETURN emp_tab IS
  2     l_result emp_tab;
  3  BEGIN
  4     SELECT emp_row(empno, ename, job, deptno)
  5       BULK COLLECT INTO l_result
  6       FROM emp
  7      WHERE deptno = p_deptno;
  8     RETURN l_result;
  9  END get_emp_dept;
 10  /

Function created

横向连接在Oracle中是自动的,没有特殊的关键字:

SQL> SELECT dept.dname, emp.empno, emp.ename, emp.job
  2    FROM dept
  3   CROSS JOIN TABLE(get_emp_dept(dept.deptno)) emp;

DNAME          EMPNO ENAME      JOB
-------------- ----- ---------- ---------
ACCOUNTING      7782 CLARK      MANAGER
ACCOUNTING      7839 KING       PRESIDENT
ACCOUNTING      7934 MILLER     CLERK
RESEARCH        7369 SMITH      CLERK
RESEARCH        7566 JONES      MANAGER
RESEARCH        7788 SCOTT      ANALYST
RESEARCH        7876 ADAMS      CLERK
RESEARCH        7902 FORD       ANALYST
SALES           7499 ALLEN      SALESMAN
SALES           7521 WARD       SALESMAN
SALES           7654 MARTIN     SALESMAN
SALES           7698 BLAKE      MANAGER
SALES           7844 TURNER     SALESMAN
SALES           7900 JAMES      CLERK

14 rows selected

Answer 2

在Oracle中,我们可以使用该函数在FROM子句中使用流水线TABLE()函数.

SQL> select * from table( get_dept_emps (10) )
  2  /

ENAME                                 SAL MGR
------------------------------ ---------- ---------------------
BOEHMER                              2450 SCHNEIDER
SCHNEIDER                            5000
KISHORE                              1300 BOEHMER

SQL>

这可以像任何其他表一样对待,例如,通过加入它:

SQL> select t.*
  2         , e.empno
  3  from
  4     table( get_dept_emps (10) ) t
  5             join emp e
  6             on e.ename = t.ename
  7  /

ENAME             SAL MGR             EMPNO
---------- ---------- ---------- ----------
BOEHMER          2450 SCHNEIDER        7782
SCHNEIDER        5000                  7839
KISHORE          1300 BOEHMER          7934

SQL>