How to execute the output result for execute immediate statment - oracle

Question

From the below query i am getting the output as below. but i am expecting the output result like the output select query to be executed again and provide the result .
Also, i want to remove the UNION ALL from last line of the output like this
select A from Table1 Union all
Select A from table2 Union All
Select A from table3 Union all
Select A from table4;
Query :
SET SERVEROUTPUT ON
Declare
v_sql varchar2(500);
v_sql2 varchar2(500);
v_prj_id varchar2(4000):='ProjectA,ProjectB,ProjectC,ProjectD';
BEGIN
Dbms_Output.Put_Line('v_prj_id='||v_prj_id);
--
FOR i IN (SELECT trim(regexp_substr(v_prj_id, '[^,]+', 1, LEVEL)) l
FROM dual
CONNECT BY LEVEL <= regexp_count(v_prj_id, ',') + 1
) LOOP
v_sql := 'select '''|| i.l ||''' AS "PRJ_ID", EVENT, email,modified_by,modified from ' || i.l ||
'.Table UNION ALL';
Dbms_Output.Put_Line (v_sql);
--
END LOOP;
EXECUTE IMMEDIATE v_sql ;
v_sql2 := RTRIM (v_sql, 'UNION ALL');
EXECUTE IMMEDIATE v_sql2 ;
Dbms_Output.Put_Line (v_sql2);
END;
/
Output :
select 'ProjectA' AS "PRJ_ID", EVENT, email,modified_by,modified from ProjectA.event UNION ALL
select 'ProjectB' AS "PRJ_ID", EVENT, email,modified_by,modified from ProjectB.event UNION ALL
select 'ProjectC' AS "PRJ_ID", EVENT, email,modified_by,modified from ProjectC.event UNION ALL
select 'ProjectD' AS "PRJ_ID", EVENT, email,modified_by,modified from ProjectD.event UNION ALL

Answer 1

EXECUTE IMMEDIATE will not provide you the SELECT statement results.
From Oracle Docs
If dynamic_sql_statement is a SELECT statement, and you omit both into_clause and bulk_collect_into_clause, then execute_immediate_statement never executes.
You have use SELECT INTO clause or BULK_COLLECT_INTO_CLAUSE and assign the values to some variable if you want to see the results of EXECUTE IMMEDIATE select values.
Something like below for single row
SET SERVEROUTPUT ON
DECLARE
L_RESULT VARCHAR2(20);
BEGIN
VSQL:= --YOUR LOGIC
EXECUTE IMMEDIATE VSQL INTO L_RESULT;
DBMS_OUTPUT.PUT_LINE(L_RESULT);
END;
/
For Multiple rows
DECLARE
TYPE T IS TABLE OF MYTABLE.ID%TYPE INDEX BY PLS_INTEGER;
MYROW T;
BEGIN
VSQL:= --YOUR LOGIC
EXECUTE IMMEDIATE VSQL BULK COLLECT INTO MYROW;
DBMS_OUTPUT.PUT_LINE(MYROW.XXX);
END;
/

Answer 2

You are doing everything right except concatenating the v_sql with original string -
SET SERVEROUTPUT ON
Declare
v_sql varchar2(500);
v_sql2 varchar2(500);
v_prj_id varchar2(4000):='ProjectA,ProjectB,ProjectC,ProjectD';
BEGIN
Dbms_Output.Put_Line('v_prj_id='||v_prj_id);
--
FOR i IN (SELECT trim(regexp_substr(v_prj_id, '[^,]+', 1, LEVEL)) l
FROM dual
CONNECT BY LEVEL <= regexp_count(v_prj_id, ',') + 1
) LOOP
v_sql := v_sql || ' select '''|| i.l ||''' AS "PRJ_ID", EVENT, email, modified_by, modified from ' || i.l ||
'.Table UNION ALL';
Dbms_Output.Put_Line (v_sql);
--
END LOOP;
EXECUTE IMMEDIATE v_sql ;
v_sql2 := RTRIM (v_sql, 'UNION ALL');
EXECUTE IMMEDIATE v_sql2 ;
Dbms_Output.Put_Line (v_sql2);
END;
/