MySQL Cursor

A cursor can’t be used by itself in MySQL. It is an essential component in stored procedures. I would be inclined to treat a cursor as a “pointer” in C/C++, or an iterator in PHP’s foreach statement.

With cursors, we can traverse a dataset and manipulate each record to accomplish certain tasks. When such an operation on a record can also be done in the PHP layer, it saves data transfer amounts as we can just return the processed aggregation/statistical result back to the PHP layer (thus eliminating the select – foreach – manipulation process at the client side).

Since a cursor is implemented in a stored procedure, it has all the benefits (and limitations) of an SP (access control, pre-compiled, hard to debug, etc).

MySQL supports cursors inside stored programs. The syntax is as in embedded SQL. Cursors have these properties:

Asensitive: The server may or may not make a copy of its result table

Read only: Not updatable

Nonscrollable: Can be traversed only in one direction and cannot skip rows

Cursor declarations must appear before handler declarations and after variable and condition declarations.

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Magento Composer

We use Composer for dependency management. Composer enables us to manage the Magento components and their dependencies.
As an integrator, you want to manage each of your Magento core components and third-party components using the Component Manager and System Upgrade.
To do so, you start by creating a Composer project from our metapackage. The metapackage installs each component so it can be centrally managed after installation.

Composer provides you with the following advantages:

Enables you to reuse third-party libraries without bundling them with source code
Component-based architecture with robust dependency management
Manages dependencies to reduce extension conflicts and compatibility issues
Versioned dependencies
Semantic versioning
Supports the PHP Framework Interoperability standard

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Beginners' Guide