Sql cursor update

Verhindert, dass über diesen Cursor Updates vorgenommen werden. Prevents updates made through this cursor. Auf den Cursor kann in einer UPDATE - oder DELETE-Anweisung nicht in einer WHERE CURRENT OF-Klausel verwiesen werden. How to update a column fetched by a cursor. Der Cursor muss Updates zulassen.

Der Name einer Cursorvariablen.

The cursor must allow updates. Declaring a Cursor for Updating Records. Introduction to Oracle Cursor FOR UPDATE. Sometimes, you want to lock a set of rows before you can update them in your program. SQL works based on set e. SELECT statement returns a set of rows which is called a result set.

This is where cursors come into play. What is a database cursor.

A database cursor is an object that enables traversal over the rows of a result set. Also see: where_current_of_ cursor. In this page you can learn how to update rows from table using delete operation in cursors. That sort of update should be far more efficient, and quicker for you to write, than a cursor. A cursor would be written something like this.

Note that you must declare variables to hold the values in the current row of the cursor , and you need to fetch each row. Suppose we have to retrieve data from two tables simultaneously by comparing primary keys and foreign keys. However, sometimes, you may want to process a data set on a row by row basis. In these types of problems, the cursor gives very poor performance as it processes. Is the name of a cursor variable.

If you plan on updating or deleting records that have been referenced by a Select For Update statement, you can use the Where Current Of statement. And no doubt about it, I consider use of cursors a bad habbit. Basically, no updates , deletes or inserts made after the cursor was open will be visible in the cursors. Den Wert der hier ausgewählten Spalte kann man später in der Cursor -Schleife verwenden. In der Regel verwendet man dafür den Primärschlüssel der Tabelle.

UPDATE DBcursor statement: You can update the data of the current row retrieved by a program by using the UPDATE statement. To handle a result set inside a stored procedure, you use a cursor.

Read-only: you cannot update data in the underlying table through the cursor. SELECT Anweisung liefern in vielen Fällen mehrere Ergebnisdatensätze zurück. Man unterscheidet explizite von impliziten CURSOR.