READ TABLE itab - ABAP Keyword Documentation

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READ TABLE itab

Quick Reference

Syntax

READ TABLE itab { table_key
| free_key
| index } result.

Effect

This statement reads a row from the internal table itab. itab is a functional operand position.

The row must be specified by naming values for either table_key for a table key, a free condition free_key, or an index index. The latter is possible only for index tables and when using a sorted secondary key. The output response result determines how and to where the row contents are read.

If the row to be read is not specified uniquely, the first suitable row is read. In the case of index tables, this row has the lowest row number of all suitable rows in the table index used.

If the internal table is specified as the return value or result of a functional method, a constructor expression, or a table expression, the value is only available when the statement is executed. Afterwards, it is no longer possible to access the internal table.

System Fields

The statement READ TABLE sets the values for the system fields sy-subrc and sy-tabix.

sy-subrc	Meaning
0	Row is found. sy-tabix is set to the row number of the entry in the primary or secondary table index used. If a hash key is used, it is set to 0.
2	Like sy-subrc equals 0. Distinguishes cases that use the addition COMPARING in result.
4	The row was not found. If the entry was determined using a binary search, sy-tabix is set to the table index of the entry before which it would be inserted using INSERT ... INDEX ..., to preserve the sort order. This is the case if, when sorted keys are used, the addition table_key or free_key was specified alongside the full table key or if the addition BINARY SEARCH was specified explicitly. Otherwise, sy-tabix is undefined (-1).
8	Like sy-subrc equals 4. If the entry was determined using a binary search, and the end of the table was reached, sy-tabix is set to the number of rows + 1.

The system fields sy-tfill and sy-tleng are also filled.

Notes

There is no implicit selection of a suitable key or index. The used table key or table index is always specified uniquely. The syntax check issues a warning if there is a suitable secondary table key but this table key is not used. This warning should be removed through using the key. However, in exceptional cases, it can be bypassed using a pragma.
As an alternative to the statement READ TABLE, table expressions can be used to allow reads to be performed on individual table rows at operand positions.
If multiple rows of an internal table are to be read, the statement LOOP generally displays better performance than using the statement READ TABLE in a loop.

Example

Reads individual table rows from a standard table in a WHILE loop. The table rows are read in reverse order with respect to the sorted secondary key sort_key. A CHECK statement exits the loop if the specified condition is not met. This construct provides the missing option of performing LOOPs in reverse order. See also the corresponding executable example with a FOR expression.

DATA itab TYPE STANDARD TABLE OF i
          WITH EMPTY KEY
          WITH NON-UNIQUE SORTED KEY sort_key COMPONENTS table_line.

itab = VALUE #( ( 2 ) ( 5 ) ( 1 ) ( 3 ) ( 4 ) ).

DATA(output) = ``.
DATA(idx) = lines( itab ).
WHILE idx > 0.
  READ TABLE itab INDEX idx USING KEY sort_key
             ASSIGNING FIELD-SYMBOL(<fs>).
  idx = idx  - 1.
  CHECK <fs> > 2.
  output = output && <fs> && ` `.
ENDWHILE.

cl_demo_output=>display( output ).

Exceptions

Non-Handleable Exceptions

Cause: When reading a table with READ ... WITH [TABLE] KEY, overlapping or duplicate keys were specified.
Runtime error: DYN_KEY_DUPLICATE
Cause: When reading a table of the type SORTED, the specified key fields have to be an initial part of the table key when BINARY SEARCH is specified.
Runtime error: ITAB_ILLEGAL_BINARY_SEARCH
Cause: No key specified.
Runtime error: ITAB_KEY_COMPONENT_MISSING
Cause: Invalid key specified when accessing a key table.
Runtime error: ITAB_KEY_ILLEGAL_COMPONENT
Cause: Key specified implicitly (invalid)
Runtime error: READ_ITAB_UC_KEY_ERROR
Cause: Invalid incompatible work area specified.
Runtime error: OBJECTS_WA_NOT_COMPATIBLE
Cause: Memory area violated when TABLES parameter accessed
Runtime error: ITAB_STRUC_ACCESS_VIOLATION

Continue
READ TABLE - table_key
READ TABLE - free_key
READ TABLE - index
READ TABLE - result
Example

Internal Tables, Key Accesses