Data not inserting to destination table - oracle

Question

I have the following block of PL-SQL code in Oracle:
DECLARE TAB VARCHAR(100);
COL VARCHAR(100);
CURSOR C_COLS IS
select DISTINCT table_name, column_name
from all_tab_columns
where OWNER = 'MyDB' AND DATA_TYPE LIKE '%VARCHAR%';
BEGIN
OPEN C_COLS;
LOOP
FETCH C_COLS INTO TAB, COL;
EXIT WHEN C_COLS%notfound;
INSERT INTO TargetTable (TABLE_NAME, COLUMN_NAME, COLUMN_VALUE)
SELECT DISTINCT TAB,
COL,
(SELECT COL FROM TAB)
FROM TAB
WHERE REGEXP_LIKE(COL, '([ABCDEFGHIJKLMNOPQRSTUVWXYZ])\d\d\d\d\d\d([ABCDEFGHIJKLMNOPQRSTUVWXYZ])', 'ix');
END LOOP;
CLOSE C_COLS;
END;
The idea is to determine which tables in my rather large database contain a certain pattern of data and to find them.
So I want to return three columns: TableName, ColumnName, Value of ColumnName.
The above runs but returns no data and I can't understand why. The query in the cursor returns results, and if I hard code the table values into a simple select statement containing my Regex, I get results. I just want one result set that contains the thousands of results I expect.
Could it be the (SELECT COL FROM TAB) I'm using to dynamically find the column_value? I wasn't sure if I could express it this way.

Answer 1

If you want to select columns dynamically you may wish to try dynamic SQL.
DECLARE
w_sql VARCHAR2(32767);
BEGIN
DBMS_OUTPUT.enable(32767);
FOR s_cols IN (
select DISTINCT
table_name
, column_name
from all_tab_columns
where owner = 'MyDB'
AND data_type LIKE '%VARCHAR%'
)
LOOP
w_sql := q'!
INSERT
INTO TargetTable (TABLE_NAME, COLUMN_NAME, COLUMN_VALUE)
SELECT DISTINCT
':TAB'
, ':COL'
, :COL
FROM :TAB
WHERE REGEXP_LIKE(:COL, '([ABCDEFGHIJKLMNOPQRSTUVWXYZ])\d\d\d\d\d\d([ABCDEFGHIJKLMNOPQRSTUVWXYZ])', 'ix')
!';
w_sql := REPLACE(w_sql, ':TAB', s_cols.table_name);
w_sql := REPLACE(w_sql, ':COL', s_cols.column_name);
EXECUTE IMMEDIATE w_sql;
END LOOP;
COMMIT;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('Error for SQL :'|| w_sql ||'; error is :'|| SQLERRM);
END;