Effect Specifies a table row in the square brackets of a table expression. This makes three alternatives possible:
Index read
Read using a free key
Read using a table key
Note The square brackets shown here indicate the optional additions and are not part of the syntax.
Example See Table Expressions, Specified Rows .
ABAP Alternative 1 ... [KEY keyname •] idx
Effect The table expression reads the row with the row number specified in idx with respect to a table index. The row is read in exactly the same way as when specifying an index, • idx [USING KEY keyname], in the statement READ TABLE. Similarly, idx is a numeric expression position and the optional KEY keyname • is equivalent to the USING KEY keyname specified. If the optional addition is not used, itab must be an index table. If the addition is used, the secondary table index of a sorted secondary key can be specified statically or dynamically. If no row is found for the specified index, the handleable exception CX_SY_ITAB_LINE_NOT_FOUND is usually raised. Exceptions to this rule are uses in the statement ASSIGN, in the predicate function line_exists, and in the table function line_index.
Effect The table expression reads the row in accordance with the specified free search key. The search is performed in exactly the same way as when specifying the free search key comp1 = operand1 comp2 = operand2 ... in the statement READ TABLE. Similarly, the components comp1 comp2 ... can be specified in accordance with the rules from the section Specifying Components. Also, compatible or convertible operands operand1 operand2 ... must be specified that are general expression positions. If no row is found for the specified free key, the handleable exception CX_SY_ITAB_LINE_NOT_FOUND is usually raised. Exceptions to this rule are uses in the statement ASSIGN, in the predicate function line_exists, and in the table function line_index.
Notes
If the free key overlaps with some or all of the primary table key, the optimizations described under READ TABLE are performed when sorted tables and hashed tables are read.
Unlike the statement READ TABLE with a free key specified, no binary searches can be forced for a table expression and it is not possible to specify explicit table key for optimizing searches using secondary keys.
ABAP Alternative 3 ... KEY keyname [COMPONENTS] ...
Effect The table expression reads the row in accordance with the explicitly specified table key.
Generally, the search is performed in exactly the same way as when specifying the table key WITH TABLE KEY [keyname COMPONENTS] ... in the statement READ TABLE. The table key must be covered completely by specifying component and no components can be specified that are not part of the table key.
If the table expression is specified as an argument of the predicate function line_exists or of the table function line_index, the search is performed as when specifying a free search key WITH KEY keyname COMPONENTS ... in the statement READ TABLE and the key is joined with a table key. A sorted table key does not have to be covered in full by specified components. For both categories of secondary keys, components can be specified that are not part of the table key. Unlike the statement READ TABLE, a table expression must specify the name of the table key and the addition COMPONENTS can be omitted. Like here, the table key keyname and the key components can be specified statically or dynamically. The operands operand1 operand2 ... are general expression positions. If no row is found for the specified table key, the handleable exception CX_SY_ITAB_LINE_NOT_FOUND is usually raised. Exceptions to this rule are uses in the statement ASSIGN, in the predicate function line_exists, and in the table function line_index.
Notes
Before the primary table key can be used explicitly in this variant, the key must first be specified using its predefined name primary_key or an alias name.
Searches using the primary table key do not have to specify it explicitly. Instead, the variant with a free search key can be used. If this covers the primary table key, it is used for optimized reads on sorted tables and hashed tables.
The differing behavior of the specified key outside and inside the functions line_exists and line_index is explained as follows:
Outside the functions, the main purpose of an explicitly specified table key is to read precisely one fully specified row.
Within the functions, the existence of a specified row (not necessarily specified in full) or, for example, a row number as the starting point of a subsequent sequential read using LOOP ... FROM is to be determined as efficiently as possible.
