Loop through all tables in database to fetch 2 rows per table - sql

Question

I have a database wherein there are multiple owners and some tables are empty.
Currently I want to sequentially execute the same fetch query against all non-empty tables of a specific owner.
I wrote the PL/SQL below, but got this error "ORA-06550: line 8, column 41: PLS-00497: cannot mix between single row and multi-row (BULK) in INTO list 06550. 00000 - "line %s, column %s:\n%s".
DECLARE
CURSOR details IS
SELECT table_name
FROM all_tables
WHERE owner = 'emp' AND num_rows > 0;
myvar all_tables.table_name%TYPE;
rows_num NATURAL := 2;
sql_stmt VARCHAR2(1000);
BEGIN
OPEN details;
LOOP
FETCH details BULK COLLECT INTO myvar LIMIT rows_num;
END LOOP;
CLOSE details;
END;
How can I fix this?
edit: New code with SELECT included:
BEGIN
OPEN details;
LOOP
FETCH details INTO my_var;
EXIT WHEN myvar%NOTFOUND;
sql_stmt := 'SELECT * FROM ' || my_var|| ' WHERE ROWNUM <= :rows_num';
EXECUTE IMMEDIATE sql_stmt;
DBMS_OUTPUT.PUT_LINE(sql_stmt);
END LOOP;
CLOSE table_cur;
END;
No more errors now but I couldn't see anything in the Dbms output.

Answer 1

As P3CONSULTING said - declare TYPE of TABLE of CURSOR%ROWTYPE and then a variable that has type that newly declared TABLE OF type. Also please do not forget to add condition in loop to avoid infinite loop. Please try this code:
DECLARE
CURSOR details IS
SELECT table_name
FROM all_tables
WHERE owner = 'emp' AND num_rows > 0;
type t_var is table of details%rowtype;
myvar t_var;
rows NATURAL := 2;
BEGIN
OPEN details;
LOOP
FETCH details BULK COLLECT INTO myvar LIMIT rows;
EXIT WHEN myvar.count = 0;
END LOOP;
CLOSE details;
END;

Answer 2

The variable into which you "BULK COLLECT" must be a "TABLE OF..." not a single ROWTYPE.

Answer 3

If you do not need an output to be of specific format, then you may use dbms_xmlgen to execute dynamic SQL and serialize result into XML document.
Setup:
create table t0
as
select *
from user_tables
where 1=0
create table t1
as
select level as id
from dual
connect by level < 5
4 rows affected
create table t2
as
select *
from all_objects
where rownum = 1
1 rows affected
create table t3
as
select *
from all_source
where rownum < 5
4 rows affected
The query:
select * from (
select
owner, table_name
, dbms_xmlgen.getxml(
replace(replace (
'select * from "schema"."table" where rownum < 3'
, 'schema', owner)
, 'table', table_name
)
) as res
from all_tables
where owner = user
)
where res is not null
OWNER
TABLE_NAME
RES
FIDDLE_AIMBWFSLKTLDLGCECWIY
T1
<?xml version="1.0"?><ROWSET> <ROW>  <ID>1</ID> </ROW> <ROW>  <ID>2</ID> </ROW></ROWSET>
FIDDLE_AIMBWFSLKTLDLGCECWIY
T2
<?xml version="1.0"?><ROWSET> <ROW>  <OWNER>SYS</OWNER>  <OBJECT_NAME>ORA$BASE</OBJECT_NAME>  <OBJECT_ID>134</OBJECT_ID>  <OBJECT_TYPE>EDITION</OBJECT_TYPE>  <CREATED>17-AUG-21</CREATED>  <LAST_DDL_TIME>17-AUG-21</LAST_DDL_TIME>  <TIMESTAMP>2021-08-17:23:05:16</TIMESTAMP>  <STATUS>VALID</STATUS>  <TEMPORARY>N</TEMPORARY>  <GENERATED>N</GENERATED>  <SECONDARY>N</SECONDARY>  <NAMESPACE>64</NAMESPACE>  <SHARING>NONE</SHARING>  <ORACLE_MAINTAINED>Y</ORACLE_MAINTAINED>  <APPLICATION>N</APPLICATION>  <DUPLICATED>N</DUPLICATED>  <SHARDED>N</SHARDED>  <IMPORTED_OBJECT>N</IMPORTED_OBJECT> </ROW></ROWSET>
FIDDLE_AIMBWFSLKTLDLGCECWIY
T3
<?xml version="1.0"?><ROWSET> <ROW>  <OWNER>SYS</OWNER>  <NAME>STANDARD</NAME>  <TYPE>PACKAGE</TYPE>  <LINE>1</LINE>  <TEXT>package STANDARD AUTHID CURRENT_USER is -- careful on this line; SED edit occurs!</TEXT>  <ORIGIN_CON_ID>1</ORIGIN_CON_ID> </ROW> <ROW>  <OWNER>SYS</OWNER>  <NAME>STANDARD</NAME>  <TYPE>PACKAGE</TYPE>  <LINE>2</LINE>  <TEXT></TEXT>  <ORIGIN_CON_ID>1</ORIGIN_CON_ID> </ROW></ROWSET>
fiddle

Answer 4

Combining everything you need the below.Which satisfies all your requirements.The Sql fiddle here
DECLARE
CURSOR details IS
SELECT a.table_name, a.owner
FROM all_tables a
WHERE a.owner = user
AND a.num_rows > 0;
type t_var is table of details%rowtype;
myvar t_var;
rows1 NATURAL := 2;
v_plsql varchar2(32767);
i number := 0;
BEGIN
OPEN details;
LOOP
dbms_output.enable;
FETCH details BULK COLLECT
INTO myvar;
if NOT myvar.EXISTS(1) THEN
EXIT;
end if;
for i in myvar.first .. myvar.last loop
if NOT myvar.EXISTS(i) THEN
EXIT;
end if;
v_plsql := 'DECLARE ' || ' type rec_row is table of ' || myvar(i)
.table_name || '%rowtype; ' || 'l_row rec_row;' || 'BEGIN ' ||
' SELECT * ' || ' BULK COLLECT INTO l_row ' ||
' FROM ' || myvar(i).table_name || ' where rownum<=' ||
rows1 || ';' ||
' if l_row.EXISTS(1) then dbms_output.put_line(''' || i ||
' table and 1 row' || '''' || '); dbms_output.put_line(''';
for rec in (select a.*,
(select max(column_id)
from all_tab_cols a
where table_name = myvar(i).table_name) max_column
from all_tab_cols a
where table_name = myvar(i).table_name
order by column_id) loop
v_plsql := v_plsql || rec.column_name;
if rec.column_id <> rec.max_column then
v_plsql := v_plsql || ',';
end if;
end loop;
v_plsql := v_plsql || '''); dbms_output.put_line(';
for rec in (select a.*,
(select max(column_id)
from all_tab_cols a
where table_name = myvar(i).table_name) max_column
from all_tab_cols a
where table_name = myvar(i).table_name
order by column_id) loop
v_plsql := v_plsql || ' l_row(1).' || rec.column_name;
if rec.column_id <> rec.max_column then
v_plsql := v_plsql || '||'',''||';
end if;
end loop;
v_plsql := v_plsql || '); end if;';
v_plsql := v_plsql ||
'if l_row.EXISTS(2) then dbms_output.put_line(''' || i ||
' table and 2 row' || '''' || '); dbms_output.put_line(''';
for rec in (select a.*,
(select max(column_id)
from all_tab_cols a
where table_name = myvar(i).table_name) max_column
from all_tab_cols a
where table_name = myvar(i).table_name
order by column_id) loop
v_plsql := v_plsql || rec.column_name || '';
if rec.column_id <> rec.max_column then
v_plsql := v_plsql || ',';
end if;
end loop;
v_plsql := v_plsql || '''); dbms_output.put_line(';
for rec in (select a.*,
(select max(column_id)
from all_tab_cols a
where table_name = myvar(i).table_name) max_column
from all_tab_cols a
where table_name = myvar(i).table_name
order by column_id) loop
v_plsql := v_plsql || ' l_row(2).' || rec.column_name;
if rec.column_id <> rec.max_column then
v_plsql := v_plsql || '||'',''||';
end if;
end loop;
v_plsql := v_plsql || '); end if;';
v_plsql := v_plsql || ' end;';
--dbms_output.put_line(v_plsql);
execute immediate v_plsql;
end loop;
exit;
END LOOP;
CLOSE details;
END;
/