Curso GeneXus

Versión: Evolution 3
Curso online

More on the For each command

We study in detail everything relative to a simple For each: base transaction and base table, indices and their relation with DB queries (optimization), and how to condition orders and filters, as well as how to program actions when the For each does not retrieve records.  

Introduction of the Procedure object with one of its multiple uses: implementing PDF listings displayed on the browser. We study two of the basic commands for that: print and For each, which enables access to an entity’s data. 
This class only has written material.
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In the “Introduction to procedures and listings. Command to query the database” video, we introduced the For each command in a procedure and we saw the Order and Where clauses. Here we will extend what was seen before, including the When clause to condition orders and filters. And also the When none clause to execute actions when the query does not retrieve anything.  We also study in detail the indices created by GeneXus automatically, and the indices created by the user: Unique to specify candidate keys, and Duplicate. 
To close we summarize the syntax of the For each command with what was shown.  

Following conclusion of the course we recommend that you view the ""Final Overview"" video where we question some of the statements that will be dealt with in upcoming training sessions. 
 
Related
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Procedures
Identifying availabe attributes
Filtering Data from a Web Panel’s Grid
Nested For Each command to list grouped data
Data Selectors: Reusing definitions
Simple For each – base table and order clause
Simple For each – base table and where clause
Simple For each – base table and order clause
Web panels: Determining the base table
More about single For each, indexes, and clauses - Ppt
More about single For each, indexes, and clauses
Orders, filters and conditions of listed data
Base tables and navigation in Smart Devices objects
Base tables and navigation in Smart Devices objects
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