FROM子句中的临时表，而不是WITH子句

Question

我有这个查询（运行得很好）：

WITH TEMPTABLE AS(
            SELECT count(CONTRACT_ID) AS no_contract, T.BRANCH_ID as branch
            FROM CONTRACT, "EMPLOYMENT" T, TABLE(T."EMPLOYEE") TT
            WHERE CONTRACT.EMPLOYEE_ID = TT.EMPLOYEE_ID
                  AND CONTRACT.CONTRACT_VT_START BETWEEN '01/01/2018' AND '30/06/2018'
            GROUP BY T.BRANCH_ID
        )
        SELECT branch
        FROM TEMPTABLE
        WHERE no_contract IN (SELECT MAX(no_contract)
                             FROM TEMPTABLE);

我想知道是否可以用其他方式代替WITH子句来完成。像这样：

SELECT count_per_branch.BRANCH
FROM (SELECT count(CONTRACT_ID) AS no_contract, BRANCH_ID AS BRANCH
      FROM CONTRACT, "EMPLOYMENT" T, TABLE(T."EMPLOYEE") TT
      WHERE CONTRACT.EMPLOYEE_ID = TT.EMPLOYEE_ID
            AND CONTRACT.CONTRACT_VT_START BETWEEN '01/01/2018' AND '30/06/2018'
      GROUP BY T.BRANCH_ID) count_per_branch
WHERE count_per_branch.no_contract =
            (SELECT max(count_per_branch.no_contract)
             FROM count_per_branch);

哪个给出了ORA-00942：“表或视图不存在” 第9行错误：

Answer 1

您可以在FROM子句中使用子查询：

FROM (SELECT count(CONTRACT_ID) ... )

您可以给它起一个别名：

FROM (SELECT count(CONTRACT_ID) ... ) count_per_branch

您可以使用该别名来限定列引用：

WHERE count_per_branch.no_contract =

但是您不能使用该别名作为另一个子查询中的行源，这是您要在此处执行的操作：

(SELECT max(count_per_branch.no_contract)
 FROM count_per_branch)

要以这种方式“重用”子查询，必须使用通用表表达式语法-即WITH子句。