ODBC Retrieval using cursors

Retrieval using cursors is conceptually similar to the singleton SELECT discussed earlier. The main difference is that since there can be multiple rows in a result set, you control when the next row is fetched into PowerScript variables.

For example, if you expect only a single row to exist in the employee table for each emp_id, use a singleton SELECT statement. In a singleton SELECT, you specify the SELECT statement and destination variables in one concise SQL statement:

SELECT emp_name, emp_salary
   INTO :emp_name_var, :emp_salary_var
   FROM employee WHERE emp_id = :emp_id_var;

However, if the SELECT may return multiple rows, you must:

  1. Declare a cursor.

  2. Open it (which conceptually executes the SELECT).

  3. Fetch rows as needed.

  4. Close the cursor.

Declaring and opening a cursor

Declaring a cursor is tightly coupled with the OPEN statement. The DECLARE specifies the SELECT statement to be executed, and the OPEN actually executes it.

Declaring a cursor is similar to declaring a variable. A cursor declaration is a nonexecutable statement just like a variable declaration. The first step in declaring a cursor is to define how the result set looks. To do this, you need a SELECT statement,  and since you must refer to the result set in subsequent SQL statements, you must associate the result set with a logical name.


Assume the SingleLineEdit sle_1 contains the state code for the retrieval:

// Declare cursor emp_curs for employee table
// retrieval.
   SELECT emp_id, emp_name FROM EMPLOYEE 
   WHERE emp_state = :sle_1.text;

// Declare local variables for retrieval.
string emp_id_var
string emp_name_var

// Execute the SELECT statement with
// the current value of sle_1.text.
OPEN emp_curs;

// At this point, if there are no errors,
// the cursor is available for further
// processing.

Scrolling and locking

Use the DBParm parameters CursorScroll and CursorLock to specify the scrolling and locking options.


Not all DBMSs support these scrolling and locking options.

Fetching rows

The ODBC interface supports the following FETCH statements. You can use them if they are supported by your backend DBMS.






Not all DBMSs support all of these FETCH statements.