在 PL/SQL 中使用带有动态 SELECT INTO 子句的绑定变量
我有一个关于在 PL/SQL 中的动态 SQL 语句中可以在哪里使用绑定变量的问题.
I have a question regarding where bind variables can be used in a dynamic SQL statement in PL/SQL.
例如，我知道这是有效的:
For example, I know that this is valid:
CREATE OR REPLACE FUNCTION get_num_of_employees (p_loc VARCHAR2, p_job VARCHAR2)
RETURN NUMBER
IS
v_query_str VARCHAR2(1000);
v_num_of_employees NUMBER;
BEGIN
v_query_str := 'SELECT COUNT(*) FROM emp_'
|| p_loc
|| ' WHERE job = :bind_job';
EXECUTE IMMEDIATE v_query_str
INTO v_num_of_employees
USING p_job;
RETURN v_num_of_employees;
END;
/
我想知道你是否可以在这样的选择语句中使用绑定变量
I was wondering if you could use a bind variables in a select statement like this
CREATE OR REPLACE FUNCTION get_num_of_employees (p_loc VARCHAR2, p_job VARCHAR2)
RETURN NUMBER
IS
v_query_str VARCHAR2(1000);
v_num_of_employees NUMBER;
BEGIN
v_query_str := 'SELECT COUNT(*) INTO :into_bind FROM emp_'
|| p_loc
|| ' WHERE job = :bind_job';
EXECUTE IMMEDIATE v_query_str
USING out v_num_of_employees, p_job;
RETURN v_num_of_employees;
END;
/
注意，我使用 SELECT INTO 语句作为动态字符串，并在 INTO 子句中使用了绑定变量.
Note I used a SELECT INTO statement as my dyamic string and used a bind variable in the INTO clause.
我目前正在旅行中，有几天不能在家里使用我的电脑，但这一直困扰着我一段时间.尝试阅读 PL/SQL 参考，但他们没有这样的选择示例.
I am currently travelling right now and won't have access to my computer back at home for a few days, but this has been nagging me for a bit. Tried reading the PL/SQL reference but they don't have an example of a select like this.
谢谢
推荐答案
不，你不能那样使用绑定变量.在您的第二个示例中，v_query_str 中的 :into_bind 只是变量 v_num_of_employees 的值的 placeholder.你的 select into 语句会变成这样:
No you can't use bind variables that way. In your second example :into_bind in v_query_str is just a placeholder for value of variable v_num_of_employees. Your select into statement will turn into something like:
SELECT COUNT(*) INTO FROM emp_...
因为 v_num_of_employees 的值在 EXECUTE IMMEDIATE 处为 null.
because the value of v_num_of_employees is null at EXECUTE IMMEDIATE.
您的第一个示例展示了将返回值绑定到变量的正确方法.
Your first example presents the correct way to bind the return value to a variable.
编辑
原始海报编辑了我在回答中提到的第二个代码块，为 v_num_of_employees 使用 OUT 参数模式而不是默认的 IN 模式.此修改使两个示例在功能上等效.
The original poster has edited the second code block that I'm referring in my answer to use OUT parameter mode for v_num_of_employees instead of the default IN mode. This modification makes the both examples functionally equivalent.
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