In this recipe, we will see the new concept of secondary keys/index within internal tables. This lets you optimize your programs when accessing data residing within an internal table.
In this recipe, we will create a program that will store all data of table VBAK into an internal table. Then we will use the secondary key in order to fetch a record pertaining to a given order number, aufnr. The primary emphasis of this recipe is on the definition and usage of a secondary key for internal tables.
For creating a program using secondary index in internal tables, follow the steps below:
- We first declare a type
ty_vbakbased on the database tablevbak. We create two keys for this table type. The first is a non-unique primary key havingvbelnas the key field. We also create a non-unique sorted secondary keysec_keyhaving one fieldaufnr. An internal tableit_vbakis defined based on the typety_vbak. In addition, a work areawa_vbakis declared for the tableit_vbak. It is always better in terms of performance to use field symbols rather than work areas. In this example, for simplicity's sake and since the performance gain is minimal, work areas have been used.
- Next, all records from table
vbakare read into tableit_vbak. - Then, the
read tablestatement is used to read the row of internal tableit_vbakpertaining toaufnr 503002using the secondary keysec_key.
In the table type definition, we specified a non-unique sorted secondary key (based on aufnr) along with the primary key. For the read statement, we also specify that the secondary key sec_key is to be used when searching in internal table it_vbak the row corresponding to aufnr 503002. Since the secondary key is used, the aufnr field is first searched in the secondary index sec_key. A faster binary search is used since it is a sorted index. The row number of the actual internal table it_vbak containing the aufnr 503002 field is then determined. Once this number is known, the relevant row is read and values assigned to the structure wa_vbak. The vbeln field is then printed. Had no secondary index been specified, a sequential search through the internal table it_vbak would have been used, which was very time consuming.