topic indexes in Application Development and Automation Discussions

indexes

Former Member — Fri, 25 May 2007 06:31:23 GMT

hai experts,

hai i wnt to know what is and index and max how many we can create for a table and how to create and delete

Re: indexes

Former Member — Fri, 25 May 2007 06:33:38 GMT

1. What is the difference between primary index and secondary index?

Primary index : Its the index which is automatically created for the PRIMARY KEY FIELD(S) of the table.

The primary index is always created automatically in the R/3 System. It consists of the primary key fields of the database table. This means that for each combination of fields in the index, there is a maximum of one line in the table. This kind of index is also known as UNIQUE.

Secondary index : Its created as and when required,

based upon other field(s) of the table,

on which search criteria is used in sqls.

Secondary indexes should contain columns that you use frequently in a selection, and that are as highly selective as possible. The fewer table entries that can be selected by a certain column, the higher that column’s selectivity. Place the most selective fields at the beginning of the index. Your secondary index should be so selective that each index entry corresponds to at most five percent of the table entries. If this is not the case, it is not worth creating the index. You should also avoid creating indexes for fields that are not always filled, where their value is initial for most entries in the table.

It is better to create few indexes not many

Reward points if useful

Regards

Anji

Re: indexes

Former Member — Fri, 25 May 2007 06:35:29 GMT

Hi,

An index can be considered a copy of a database table that has been reduced to certain fields. This copy is always in sorted form. Sorting provides faster access to the data records of the table, for example using a binary search. The index also contains a pointer to the corresponding record of the actual table so that the fields not contained in the index can also be read.

You can search a table for data records that satisfy certain search criteria faster using an index.

The primary index contains the key fields of the table and a pointer to the non-key fields of the table. The primary index is created automatically when the table is created in the database.

Regards,

Padmam.

Re: indexes

Former Member — Fri, 25 May 2007 06:36:34 GMT

Hi,

Maximum of 9 secondary indexes permitted.

Regards,

Srinivas

Re: indexes

Former Member — Fri, 25 May 2007 06:39:23 GMT

Hi,

An index is an efficiency mechanism for quickly finding rows within a table. It is needed because data is stored in a table in the order in which it was added . A table index is a copy of one or more columns stored in sorted order with pointers to the original rows.

To <b>create a secondary index</b>:

1.Display the table. You should begin on the Dictionary: Table/Structure: Display Fields screen.

2.Press the Indexes. . . button on the Application toolbar (or choose the menu path Goto->Indexes. . .).

3.If secondary indexes already exist, a list of them will be displayed in a dialog box named Indexes for Table xxxxx. To create an index, press the Create button. The Create Index dialog box will be displayed.

4.If no secondary indexes exist, you will not see a list of indexes. Instead, you will see the Create Index dialog box immediately.

5.Enter an index id in the Index ID field. Customer indexes should begin with Y or Z, although the system does not enforce this.

6.Press the Continue button. The ABAP/4 Dictionary: Table: Maintain Index screen is displayed.

7.In the Short Text field, type a description of the index.

8.In the Fld Name column, type the fields that should comprise the index in the order that they should be sorted.

9.If the values in these fields when taken together must always be unique, tickmark the Unique Index check box.

10.Press the Save button on the Application toolbar. The values in the Status fields are now New and Saved, and directly below them the message Does not exist in the database appears. Also, the message Index xxx to table xxxxx was saved appears at the bottom of the window in the status bar.

11.Press the Activate button on the Application toolbar. The system generates SQL and sends it to the RDBMS, creating the index in the database. If successful, the Status fields read Active and Saved, and below the status fields the message Exists in the database appears. The DB Index Name field will contain the name of the index in the database. Also, in the status bar, the message Index xxxxx was successfully activated. is displayed.

12.Press Back. The Indexes for Table xxxxx screen is displayed.

13.Press Cancel to return to the Dictionary: Table/Structure: Display Fields screen.

To <b>delete a secondary index</b>:

1.Display the table. You should begin on the Dictionary: Table/Structure: Display Fields screen.

2.Press the Indexes. . . button on the Application toolbar (or choose the menu path Goto->Indexes. . .). If you see the Create Index dialog box, no secondary indexes exist for the table, so you cannot delete one. If secondary indexes already exist, a list of them will be displayed in a dialog box named Indexes for Table xxxxx.

3.Double-click on the index you want to delete. The ABAP/4 Dictionary: Table: Display Index screen is shown.

4.Press the Display <-> Change button on the Application toolbar. The screen switches to change mode, and the title of the screen reads ABAP/4 Dictionary: Table: Maintain Index.

5.Choose the menu path Index->Delete. The Delete Index Definition dialog box appears asking you to confirm the delete request.

6.Press the Yes button to delete the index. You are returned to the Dictionary: Table/Structure: Display Fields screen. The message Index xxxxx deleted appears in the status bar.

Hope this helps.

Reward if helpful.

Regards,

Sipra