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CORRESPONDING - Lookup table

Other versions: 7.31 | 7.40 | 7.54

Syntax


... CORRESPONDING dtype|#( itab FROM lookup_tab 
  
                 
           USING [KEY key_name] s1 = t1 s2 = t2 ... 

                 
              [mapping]  ) ...

Effect

This variant of the component operator CORRESPONDING can only be used for internal tables. The expression constructs an internal table from the components of the internal table itab and a lookup table lookup_tab. The lines of the internal table come from a comparison of itab and lookup_tab. The target type specified using dtype or # must be a table type. The parameters itab and lookup_tab expect internal tables whose row type must be structured. Also, itab must be convertible to the target type. itab and lookup_tab are general expression positions.

The result of the expression is created in the following steps:

  • First, an intermediate result of the type of the internal table itab is constructed as follows: For each row in itab, a row is searched for in lookup table lookup_tab that has the same content in the columns s1, s2, ... as the columns t1, t2, ... of the row in itab. The search must take place using a sorted table key or a hash key (see below). If the key is not unique, the first row found is used.
  • If no row like this is found, a row with the unchanged content of the row in itab is inserted into the intermediate result.
  • If a row like this is found, a row is inserted into the intermediate result that is the result of an assignment of the row found in itab to the current row in lookup_tab. By default, the assignment is made in accordance with the rules of MOVE-CORRESPONDING for structures with the addition EXPANDING NESTED TABLES, with the exception that the components used for searches are not assigned by default: The components s1, s2, ... from lookup_tab used for searches are by default not assigned to the identically named components of itab and the components t1, t2, ... from itab used for searches are not assigned the identically named components from lookup_tab.
  • The intermediate result of the type of the table itab is assigned to the result of the expression in accordance with the regular assignment rules for internal tables and, if necessary, converted to the target type.

This means that the component by component assignment takes place between the lookup table lookup_tab as the source table and an intermediate result with the type of itab as the target table. A mapping rule mapping can be used to override the default assignment of identically named components and the default exclusion of the components s1, s2, ... and t1, t2, ... It is not possible to specify the same internal table for itab and lookup_tab, otherwise there can be a runtime error CORRESPONDING_SELF.

The search for the row in lookup_tab must take place using a sorted table key or a hash key:

  • If the addition KEY is not specified, a sorted table or a hashed table must be specified for lookup_tab.
  • If the addition KEY is specified, the key key_name specified after it is used. The following can be specified for key_name:
  • The primary key using its predefined name primary_key or using an alias. If the primary key is specified, lookup_tab must be a sorted table or a hashed table.

The comparison fields s1, s2, ... must cover the full table key.


Notes

  • Unlike the basic form, this variant does not have the addition DEEP. Instead, it always behaves as if DEEP were specified. The addition BASE cannot be specified either.

  • Generally, the type of itab and the target type must be identical.

  • In one common use case, an existing internal table itab is enriched with information from the lookup table lookup_tab. Here, the constructor expression is assigned to the same internal table as specified for itab. In this case, the expression is optimized internally to work directly with itab without creating an intermediate result.

  • If the constructor expression is not assigned to the internal table specified for itab or if this table is not known statically, the temporary intermediate result with the type itab must be created in full. This produces a syntax check warning that can be hidden by a pragma.

  • If the same table is specified for itab and lookup_tab, a temporary copy of the table must be created as a target table of the assignment and a syntax check warning that can be hidden is produced here too. If this is not detected until runtime, the information needed to create the necessary temporary copy of the target object is missing and runtime error CORRESPONDING_SELF occurs.


Example

Rows of internal table itab1 that are present in internal table itab2 are passed to itab1.

TYPES: 
  BEGIN OF line, 
    value   TYPE i, 
    comment TYPE string, 
  END OF line, 
  itab1 type STANDARD TABLE OF line WITH EMPTY KEY, 
  itab2 TYPE HASHED TABLE OF line WITH UNIQUE KEY value. 

DATA(itab1) = VALUE itab1( for i = 1 UNTIL i >= 10 ( value = i ) ). 
DATA(itab2) = VALUE itab2( ( value = 2 comment = `...` ) 
                           ( value = 3 comment = `...` ) 
                           ( value = 5 comment = `...` ) 
                           ( value = 8 comment = `...` ) ). 

itab1 = CORRESPONDING itab1( itab1 FROM itab2 USING value = value ). 

cl_demo_output=>display( itab1 ).

Executable Examples