Sql cursor

Regeln für Bezeichner entsprechen. SELECT statement returns a set of rows which is called a result set. However, sometimes, you may want to process a data set on a row by row basis.

SQL works based on set e. What is a database cursor. A database cursor is an object that enables traversal over the rows of a result set. A cursor declaration initializes the cursor into memory.

Open: In order to put that cursor to work, we have to open it first. When we open a cursor , the memory is allotted to it. Fetch: Fetching is the process of retrieving the data from the cursor. The set of rows the cursor holds is referred to as the active set. These cursors can also be named so that they can be referred from another place of the code.

In der Regel verwendet man dafür den Primärschlüssel der Tabelle. But be advise take this. 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. This is a common approach for developers.

In einigen speziellen Fällen müssen Sie Ihren Datensatz jedoch Datensatz für Datensatz durchlaufen und einige Aktionen ausführen. Other times, you may want to guarantee that such updates or deletions can’t be made. OPTIMISTIC: It specifies that positioned updates or deletes made through the cursor do not succeed if the row has been updated since it was read into the cursor. If you want to prevent.

It instead uses comparisons of timestamp column values, or a checksum value if the table has no timestamp column, to. Let’s look at some examples of using the cursor FOR LOOP statement to see how it works. The following example declares an explicit cursor and uses it in the cursor FOR LOOP statement.

The cursor can also be named to use it further in the program by a programmer. As we get more complicate we can declare cursors with parameters. For example, you could define a cursor called cas below. Cursor with parameters.

You will learn step by step how to use a cursor to loop through a set of rows and process each row individually. There may be times when you need to loop through a et a row at a time and perform a certain action for each row. This temporary work area is used to store the data retrieved from the database, and manipulate this data.

Most of the time, cursors can be very easily replaced using joins. There are different types of cursors in sql server as listed.