Getting ORA-00904 invalid identifier with pl/sql loop - sql

Question

When attempting to use a list of tables as segment names for a query against dba_segments I get an ORA-00904: invalid identifier error.
I've tried moving around various quotes in case it's a syntax error, but I'm not sure what the issue might be.
declare
v_sql_c1 varchar2 (1000);
V_dblink varchar2(100) := 'DB1';
begin
for c1 in (select * from TABLE_LIST)
loop
execute immediate' select /*+parallel*/ bytes from dba_extents '|| '#' ||V_dblink ||' a '
||' where segment_name ='||
c1.table_name
into v_sql_c1;
dbms_output.put_line(v_sql_c1);
end loop;
end;
/
I would like ideally for this to report a value for 'bytes' in every row in the table_name column of table_list, which is the same as the segment_name column of dba_segments.
Can anyone help?

Answer 1

This is what you currently have:
SQL> CREATE TABLE table_list (table_name VARCHAR2 (20));
Table created.
SQL> INSERT INTO table_list VALUES ('EMP');
1 row created.
SQL> set serveroutput on;
SQL> DECLARE
2 v_sql_c1 VARCHAR2 (1000);
3 V_dblink VARCHAR2 (100) := 'DB1';
4 v_sql VARCHAR2 (1000);
5 BEGIN
6 FOR c1 IN (SELECT * FROM TABLE_LIST)
7 LOOP
8 v_sql :=
9 ' select /*+parallel*/ bytes from dba_extents '
10 || '#'
11 || V_dblink
12 || ' a '
13 || ' where segment_name ='
14 || c1.table_name;
15
16 DBMS_OUTPUT.put_line (v_sql);
17
18 -- EXECUTE IMMEDIATE v_sql INTO v_sql_c1;
19
20 DBMS_OUTPUT.put_line (v_sql_c1);
21 END LOOP;
22 END;
23 /
select /*+parallel*/ bytes from dba_extents #DB1 a where segment_name =EMP
PL/SQL procedure successfully completed.
SQL>
See? An invalid SELECT statement.
But, if you
remove space in front of a database link name
apply single quotes to segment_name
you'll get something that might work:
SQL> DECLARE
2 v_sql_c1 VARCHAR2 (1000);
3 V_dblink VARCHAR2 (100) := 'DB1';
4 v_sql VARCHAR2 (1000);
5 BEGIN
6 FOR c1 IN (SELECT * FROM TABLE_LIST)
7 LOOP
8 v_sql :=
9 ' select /*+parallel*/ bytes from dba_extents'
10 || '#'
11 || V_dblink
12 || ' a '
13 || ' where segment_name ='
14 || CHR (39)
15 || c1.table_name
16 || CHR (39);
17
18 DBMS_OUTPUT.put_line (v_sql);
19
20 -- EXECUTE IMMEDIATE v_sql INTO v_sql_c1;
21
22 DBMS_OUTPUT.put_line (v_sql_c1);
23 END LOOP;
24 END;
25 /
select /*+parallel*/ bytes from dba_extents#DB1 a where segment_name ='EMP'
PL/SQL procedure successfully completed.
SQL>
Basically, you should always display statement you'll be running as a dynamic SQL, make sure it is correct, and then actually EXECUTE IMMEDIATE it.