ABAP CDS Views and Internal Tables

Core Data Services (CDS)

• CDS view entities support parameters.
• Parameters are defined using the @ symbol followed by a variable or expression.
• Some examples of valid parameters are:
  • $session.system_date (system date)
  • @ (cl_abap_context_info->get_system_date()) (system date)
  • A literal date value in the format YYYYMMDD ('20230101').

CDS Views - Joining

• CDS views can be joined based on their fields.
• You can use the ON clause in a JOIN statement to define the join condition.
• The JOIN clause should reference the fields from the views you want to join.
• You cannot use the $projection variable in the ON clause because it represents the view's projection, not individual fields.

ABAP Internal Tables

• You can utilize the itab1 = corresponding #( itab2) statement to copy data from one internal table (itab2) to another (itab1).
• This statement will copy fields with the same name and data type.
• Both tables must have at least one field name in common.

ABAP String Manipulation

• You can use ABAP SQL to manipulate strings within a SELECT statement.
• The substring, upper, and left functions can be used to extract specific characters from a string.
  • substring(upper('mr joe doe'), 4, 3) will extract the substring "JOE" from the string.
  • upper(left( 'mr joe doe', 6)) will extract the substring "MR JOE" and convert it to uppercase.

ABAP Data Types

• When assigning a variable to another variable, the types must be compatible to avoid truncation or rounding issues.
• The TYPE keyword is used to declare a variable's data type.
• Examples of data types:
  • p - Packed number, c - Character, string - Character string

CDS View Activation Error

• A CDS view with a union must have matching field names (same names) and data types (compatible types) for successful activation.
• If the field names in the union do not match, the activation will fail. Similarly, if the field types are incompatible, the activation will fail.

ABAP SQL - Selecting From CDS Views

• You can select data from a CDS view using SELECT statements in ABAP SQL.
• The FROM clause should reference the view name, for example:
  • SELECT mat FROM demo_sales_cds_material_ve (select the field named 'mat' from the view demo_sales_cds_material_ve)

ABAP Internal Table Types

• There are different types of internal tables in ABAP:
  • Standard Table - Default internal table type, no specific ordering.
  • Sorted Table - Table with entries ordered by SORT statement.
  • Hashed Table - Table with entries accessed using a hash key for fast access.
  • Index Table - Table with entries accessed by a specific index number.

ABAP Variables

• Variables in ABAP can be declared with different data types:
  • Simple variable - Stores a single value.
  • Internal table - Stores a collection of rows.
  • Structure- Groups data into logical units, similar to classes.

ABAP SQL - Case Distinctions

• CASE statements in ABAP SQL allow you to evaluate different conditions and return specific values.
• You can use CASE statements to create conditional logic within WHERE clauses and SELECT statements.
• Valid case distinctions include WHEN clauses and ELSE clauses.

ABAP Internal Table Sorting

• Sorting is performed using the SORT statement.
• You can define sorting conditions based on fields and their order (ascending or descending).
• SORT itab BY field1 field2 will sort the internal table itab ascending by field1 and then field2.

ABAP Internal Table Modifications

• The MODIFY statement is used to modify the contents of an existing row in an internal table.

ABAP Security - Access Control Objects

• Access Control Objects (ACOs) define access rights to database tables.
• They use clauses like:
  • WHERE to define specific conditions for access.
  • GRANT to define access rights.
  • REVOKE to remove access rights.

ABAP SQL Syntax

• Conventions for SELECT statements in ABAP Open SQL:
  • The INTO TABLE @gt flights clause should appear after the FIELDS clause within the SELECT statement.

ABAP Predicate Conditions

• CAST can be used to convert data types in ABAP.
• To ensure a valid CAST operation, the data type being converted should be a SUPPLIED type (meaning it has a value).

ABAP Logical Expression Evaluation

• The logical operators in ABAP are evaluated in the following order:
  • NOT - highest priority
  • AND - medium priority
  • OR - lowest priority

ABAP Database Table Definitions

• Key parts of defining a database table:
  • Field list - Defines the fields and their data types.
  • Semantic table attributes - Defines the table's characteristics.
  • Extension - Allows you to add custom fields and logic.