oracle dynamic query fetch cursor variables through sql - sql

Question

Little help needed. i have a dynamic query that outputs 4 column names and two table names into 6 cursor variables. Now i need to use the cursor variables to select the first 4 columns and then from the two table names using the cursor variables since those contain the data think something with a fetch through query using a variable that contains the query but i don’t know how to go about that. here’s what i have now i just need to fetch the cursor variables and runt hem into a query
DECLARE
arow VARCHAR2 (1000);
column1 VARCHAR2 (50);
column2 VARCHAR2 (50);
column3 VARCHAR2 (50);
column4 VARCHAR2 (50);
table1 VARCHAR2 (50);
table2 VARCHAR2 (50);
match VARCHAR2 (50);
match1 VARCHAR2 (50);
sql_statement VARCHAR2 (500);
BEGIN
FOR arow IN (SELECT column_name_old,
column_name_new,
column_name_old_2,
column_name_new_2,
table_name_old,
table_name_new
FROM A550003.META_DATA_TABLE)
LOOP
sql_statement :=
'INSERT'
|| ' '
|| 'INTO'
|| ' '
|| 'a550003.MATCH_TABLE'
|| ' '
|| 'SELECT '
|| arow.column_name_old
|| ', '
|| arow.column_name_new
|| ', '
|| 'DECODE( '
|| arow.column_name_old
|| ', '
|| arow.column_name_new
|| ','
|| '1'
|| ','
|| '0)'
|| 'AS'
|| ' '
|| 'MATCH'
|| ','
|| arow.column_name_old_2
|| ', '
|| arow.column_name_new_2
|| ','
|| 'DECODE( '
|| arow.column_name_old_2
|| ', '
|| arow.column_name_new_2
|| ','
|| '1'
|| ','
|| '0)'
|| 'AS'
|| ' '
|| 'MATCH1'
|| ' FROM '
||' '
|| arow.table_name_old
|| ', '
|| arow.table_name_new
|| ' WHERE '
|| arow.column_name_old
|| '='
|| arow.column_name_new
|| '(+)';
DBMS_OUTPUT.PUT_LINE (sql_statement);
EXECUTE IMMEDIATE sql_statement;
COMMIT;
END LOOP;
END;

Answer 1

First of all you sql_statement is wrong. You should set the value of this variable to sth like this (when you will get all needed names):
sql_statement := 'SELECT '
|| column1
|| ', '
|| column2
|| ', '
|| column3
|| ', '
|| column4
|| ' FROM '
|| table1
|| ', '
|| table2
|| ' WHERE '
|| -- JOIN_CONDITION
And then you can use EXECUTE IMMEDIATE statement:
EXECUTE IMMEDIATE sql_statement
INTO col1_val
,col2_val
,col3_val
,col4_val
;
Of course variables col[1..4]_val have to be declared.
Also watch out for SQL Injection.

Answer 2

It must be this:
sql_statement := 'SELECT '
|| column1 || ', ' || column2 || ', ' || column3 || ', ' || column4
|| ' FROM ' || table1 || ', ' || table2
|| ' WHERE ' || column1 ||'=' ||column2||'(+)';
EXECUTE IMMEDIATE sql_statement INTO col1_val, col2_val, col3_val, col4_val;
or preferably
sql_statement := 'SELECT '
|| column1 || ', ' || column2 || ', ' || column3 || ', ' || column4
||' FROM '||table1||' LEFT OUTER JOIN '||table2||' ON '||column1||'='||column2;
EXECUTE IMMEDIATE sql_statement INTO col1_val, col2_val, col3_val, col4_val;
For debugging DBMS_OUTPUT.PUT_LINE (sql_statement); will be usefull!
Then you don't need a Ref-Cursor, simply do:
BEGIN
For aRow in (SELECT * FROM a550003.meta_data_table) LOOP
sql_statement := 'SELECT '||aRow.column1||','||aRow.column2 ...
END LOOP;
END;