Question

我想知道plsql中是否存在类似于表和列的别名。我想做这样的事情（伪代码）：

if (foo) 
then
   alias bla_table = tablenameA
   alias bla_column = coulmnnameA
else
   alias bla_table = tablenameB
   alias bla_column = coulmnnameB
end

select bla_column from bla_table;

Answer 1

有一些方法可以存档类似的效果;可能最简单的方法是声明一个游标，并根据if路径打开它以进行不同的查询。

取自Oracle Documentation：

的示例

CREATE PACKAGE emp_data AS
   TYPE EmpCurTyp IS REF CURSOR RETURN emp%ROWTYPE;
   PROCEDURE open_emp_cv (emp_cv IN OUT EmpCurTyp, choice IN INT);
END emp_data;

CREATE PACKAGE BODY emp_data AS
   PROCEDURE open_emp_cv (emp_cv IN OUT EmpCurTyp, choice IN INT) IS
   BEGIN
      IF choice = 1 THEN
         OPEN emp_cv FOR SELECT * FROM emp WHERE comm IS NOT NULL;
      ELSIF choice = 2 THEN
         OPEN emp_cv FOR SELECT * FROM emp WHERE sal > 2500;
      ELSIF choice = 3 THEN
         OPEN emp_cv FOR SELECT * FROM emp WHERE deptno = 20;
      END IF;
   END;
END emp_data;

PL / SQL表和列别名

1 个答案: