Oracle 中的 SQL Server APPLY 相当于什么?
我是 Oracle 的新手.是否有与 SQL Server APPLY 相同的内置关键字?
I am new to Oracle. Is there a builtin keyword does the same job of SQL Server APPLY?
推荐答案
我认为相当于 Oracle 中的 APPLY 子句称为横向 JOIN.Oracle 中的横向连接是将表 A 与输出行的函数 F 连接起来，该函数将 A 的列作为参数.
I think the equivalent of the APPLY clause in Oracle is called a lateral JOIN. A lateral join in Oracle is when you join a table A with a function F that outputs rows and this function has columns of A as parameters.
让我们用这个设置构建一个小例子:
Let's build a small example with this setup:
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
在 Oracle 中横向连接是自动的，没有特殊的关键字:
A lateral join is automatic in Oracle, there is no special keyword:
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
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