Original: http://ntk2006.blog.sohu.com/135331235.html
Cursor ConceptCursors provide a flexible way to retrieve and operate data from tables. cursors are mainly used on servers to process SQL statements sent from clients to servers, or data
I. cursor Recognition
Cursor allows you to access the result set returned by SQL Server row by row.A major reason for using cursor is to convert the set operation into a single record processing method.After retrieving data from a database using
Cursor is a complex concept in the database field, because it contains shared cursor and session cursor. The two have different concepts and forms.The concept of shared cursor is easy to confuse with the cursor defined in SQL statements. This
Today, we will briefly summarize the usage of cursor in PL/SQL.
Cursor category:
-- Explicit cursor-- Static cursor |
| -- Implicit cursorCursor |-- Strong type (Restriction), specifying the return type-- Dynamic Cursor -- ref cursor |-- Weak type
one. Adaptive cursor Sharing (adaptive Cursor sharing) Description
1.1 ACS Overview
Binding variables Enable Oracle DB to share a single cursor for multiple SQL statements to reduce the amount of shared memory used for parsing SQL statements.
Cursor is a method for processing data. To view or process data in a result set, A cursor provides the ability to forward or backward data in a result set by one or more rows. We can use a cursor as a pointer, which can specify any position in the
CursorA cursor is a data buffer opened by the system for the user, which holds the results of the SQL statement execution. Each cursor area has a name that allows the user to retrieve the record from the cursor one at a-and assign it to the main
server| Cursor Sql-server Declaration cursor
Each cursor must have four components, these four key parts must conform to the following order;
1.DECLARE Cursors
2.OPEN Cursors
3. Fetch information from a cursor
4.CLOSE or deallocate cursors
Usually
I recently handled some memory leaks in my work. In this process, I found some basic problems, instead of causing memory leaks, such as static variables, cursor shutdown, threads, timer, anti-Registration, bitmap, etc. I have made some statistics
Cursors are evil!
In relational databases, we think about queries in a set. The cursor breaks this rule and changes the way we think about it into a row-by-row approach. For C-like developers, this approach is more comfortable.
The normal way of
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