Use the value of a string variable in SQL FOR-IN (SELECT) loop - sql

Question

I have an SQL procedure, that should execute a FOR-IN (SELECT ..) loop, where the SELECT content should vary depending on some input parameters. My idea was to store the SELECT string into a variable, and then try to extract the variable value in the FOR-IN loop but without success so far (earlier there was a fix SELECT statement used there, that's what I am trying to replace now). The code looks about as follows
PROCEDURE run(p_boolean BOOLEAN)
IS
BEGIN
DECLARE
v_mystring VARCHAR(50);
BEGIN
IF p_boolean = TRUE
THEN
v_mystring := 'SELECT something...';
ELSE
v_mystring := 'SELECT something else...';
END IF;
FOR p_table_name IN (would-like-to-use-the-value-of-v_mystring-here-some-way)
LOOP
...
END LOOP;
END;
END;
Being quite novice in SQL, it might well happen that the entire concept of trying to use a string variable value here is wrong. I browsed through some tutorials and tried some other ideas (e.g. cursor), but no result. Any idea is appreciated

Answer 1

Assuming Oracle's PL/SQL ,You can open a REFCURSOR using dynamic String and call it in a LOOP..
PROCEDURE run(p_boolean BOOLEAN)
IS
BEGIN
DECLARE
v_mystring VARCHAR(50);
v_my_ref_cursor sys_refcursor;
BEGIN
IF p_boolean = TRUE
THEN
v_mystring := 'SELECT something...';
ELSE
v_mystring := 'SELECT something else...';
END IF;
OPEN v_my_ref_cursor FOR v_mystring;
LOOP
FETCH v_my_ref_cursor INTO your_variables/record
EXIT WHEN v_my_ref_cursor%NOTFOUND;
..
END LOOP;
CLOSE v_my_ref_cursor;
END;
END;