How to use a PL/SQL cursor to determine if there is data.

In PL/SQL, cursors can be used to determine if there is data. Here is an example code:

DECLARE
  CURSOR c_data IS
    SELECT * FROM your_table; -- 替换成你的查询语句
  
  v_data_exists BOOLEAN := FALSE;
BEGIN
  OPEN c_data;
  
  FETCH c_data INTO ...; -- 可以使用 FETCH INTO语句来获取数据，如果获取到了数据，说明有数据存在
  
  IF c_data%FOUND THEN
    v_data_exists := TRUE;
  END IF;
  
  CLOSE c_data;
  
  IF v_data_exists THEN
    DBMS_OUTPUT.PUT_LINE('数据存在');
  ELSE
    DBMS_OUTPUT.PUT_LINE('数据不存在');
  END IF;
END;

In the above code, a cursor c_data is first defined to retrieve data from the database. The cursor is then opened using the OPEN statement, and the FETCH INTO statement is used to attempt to retrieve data. If data is successfully retrieved, v_data_exists is set to TRUE. Finally, the existence of data is determined based on the value of v_data_exists, and the corresponding result is output. The cursor is then closed.

Please note that the “…” part in the code above needs to be replaced according to the actual situation. Determine the variables in the FETCH INTO statement based on your query.