Dynamic SQL LOOP - sql

Question

Dynamic SQL is not my friend, basically the idea is that I can use the procedure with the "p_in_table" paramter to get the number of rows contained in the table.
CREATE OR REPLACE PROCEDURE how_many_rows(p_in_table VARCHAR2)
IS
TYPE cur_cur IS REF CURSOR;
v_cur_cur cur_cur;
v_rowcount NUMBER(28);
v_cur_txt VARCHAR2(299);
BEGIN
v_cur_txt := 'SELECT * FROM ' || p_in_table;
OPEN v_cur_cur FOR v_cur_txt;
LOOP
v_rowcount := v_cur_cur%ROWCOUNT;
EXIT WHEN v_cur_cur%NOTFOUND;
END LOOP;
CLOSE v_cur_cur;
dbms_output.put_line(v_rowcount);
END;
Would preciate it if someone would tell me what am I doing wrong?

Answer 1

The problem is that you not iterating through cursor - no fetch statement or something like that, so, basically, you have an infinite loop. To avoid this you need to do something like this:
CREATE OR REPLACE PROCEDURE how_many_rows
(p_in_table VARCHAR2) IS
TYPE cur_cur IS REF CURSOR;
v_cur_cur cur_cur;
v_rowcount NUMBER(28);
v_cur_txt VARCHAR2(299);
v_row SOME_TABLE%ROWTYPE; --add row variable
BEGIN
v_cur_txt := 'SELECT * FROM '|| p_in_table;
OPEN v_cur_cur FOR v_cur_txt;
LOOP
v_rowcount := v_cur_cur%ROWCOUNT;
FETCH v_cur_cur INTO v_row; --fetch a row in it
EXIT WHEN v_cur_cur%NOTFOUND;
END LOOP;
CLOSE v_cur_cur;
DBMS_OUTPUT.PUT_LINE(v_rowcount);
END;
But, as you can see, to do this you need to know, what table you're quering, so this is not general solution. Maybe there is a workaround for this, but i suggest, you use more simple and efficient approach, for example with EXECUTE IMMEDIATE:
CREATE OR REPLACE PROCEDURE HOW_MANY_ROWS(p_in_table VARCHAR2)
IS
v_tmp NUMBER;
BEGIN
EXECUTE IMMEDIATE 'SELECT COUNT(1) FROM ' || p_in_table INTO v_tmp;
DBMS_OUTPUT.PUT_LINE(v_tmp);
END;
Ok, I gave a thought on how to achieve this using your way, and here is what i've ended up with - just fetch ROWNUM from your table, every table has it and you know it's type - NUMBER. So this procedure will work in general case:
CREATE OR REPLACE PROCEDURE how_many_rows
(p_in_table VARCHAR2) IS
TYPE cur_cur IS REF CURSOR;
v_cur_cur cur_cur;
v_rowcount NUMBER(28);
v_cur_txt VARCHAR2(299);
v_row NUMBER; --add rownum variable
BEGIN
v_cur_txt := 'SELECT ROWNUM FROM '|| p_in_table; --select only rownum from target table
OPEN v_cur_cur FOR v_cur_txt;
LOOP
v_rowcount := v_cur_cur%ROWCOUNT;
FETCH v_cur_cur INTO v_row; --fetch rownum in it
EXIT WHEN v_cur_cur%NOTFOUND;
END LOOP;
CLOSE v_cur_cur;
DBMS_OUTPUT.PUT_LINE(v_rowcount);
END;