A cursor is a database object used to traverse through a set of rows returned by a SQL query, and perform operations on each row. Programming a SQL Server cursor involves creating a cursor, defining its properties and executing it to retrieve and manipulate data.
To program a SQL Server cursor, you first need to define its properties such as its name, data type, and the SQL statement that will return the data. This can be done using the DECLARE CURSOR statement, which takes in parameters such as the cursor name, the SELECT statement, and the type of cursor (static, dynamic or keyset).
Once the cursor is declared, you can fetch the data using FETCH statements, which retrieve rows from the result set one at a time. You can also use WHILE loop statements to iterate through the rows until there are no more rows to fetch.
Inside the loop, you can manipulate the data by performing various operations such as updating or deleting rows. After each operation, you should update the cursor using the FETCH statement to retrieve the next row and continue the loop.
Once you have finished iterating through the result set, you should close the cursor using the CLOSE statement and deallocate it using the DEALLOCATE statement.
It’s important to note that cursors can have a negative impact on database performance, especially when working with large result sets. As such, it’s important to use cursors judiciously and optimize queries to reduce the need for them.
Programming a SQL Server cursor involves creating, declaring, fetching, iterating, manipulating, closing and deallocating the cursor. It’s a powerful tool for manipulating data, but should be used with caution to avoid performance issues.
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