Primary key and foreign relationship in sap abap tutorial

consistency - How to create two compound foreign keys in ABAP - Stack Overflow

primary key and foreign relationship in sap abap tutorial

They allow you to find the relation between two tables. Keys In this tutorial, you will learn: Difference Between Primary key & Foreign key. Home» SAP ABAP» SAP ABAP Tutorial» SAP Data Dictionary Tutorial In the ABAP/4 Dictionary, relationships can be defined between tables. In T1, the foreign key fields are assigned to the primary key fields of T2. Whats is foreign keys Foreign keys describe the relationship between the tables in the ABAP Data Dictionary. This category applies when the foreign key is neither a primary key of the foreign key table nor the candidate key.

As the name implies, a concatenated key is a joining of multiple single keys. Primary Keys A primary key is a key which has been chosen to be the principal or primary representative attribute for that row of data. The primary key is unique and that attribute is then used throughout the database and is accessed and passed around to other tables as the representative attribute for the data in question.

primary key and foreign relationship in sap abap tutorial

In practice, the primary key attribute is also marked as NOT NULL in most databases, meaning that attribute must always contain a value for the record to be inserted into the table. For example, imagine a User gets a new email address, which then causes all past primary key associations made using the old email address to become invalid when using the new email address.

For this reason among othersmost primary keys use a number or unique string, such as a UUID. This simply means that the database engine itself automatically assigns each new record in that table a unique primary key value that is incrementally larger than all previous values.

primary key and foreign relationship in sap abap tutorial

However, most developers agree that this practice is out of date and exposes unnecessary security flaws for the system when used for some tables that represent certain data. For example, imagine all User records are assigned an auto-incremented primary key value, know as the id attribute. If a malicious person discovers that the id attribute of a given user e.

John Smith is the valuethis exposes a bit of information already. First, it indicates that there are likely a minimum of at least other users in the system, or were at some point.

You can choose a size category between 0 and 4. Each category is assigned to a fixed size of memory area extentdepending on the database system used.

Buffering can considerably enhance the performance of the system. The buffers are located locally on the application servers of the system. The records of buffered tables are thus read from the local buffer of the application server on which the accessing transaction is running.

Only Transparent and Pooled table can be buffered. Buffering is not permitted for Cluster Tables. Using Indexes records in the tables can be searched in a faster way.

Abap Tutorial: Step by step process for Creating Foriegn Key relation in abap

Let us now go through the procedure of creating Tables, Domains, Data Elements: While creating the table we will also see how to create a Data Element and Domain. Enter a name of the table in the Object Name box and click on the Tables radio button for creating the table.

The name of the table should begin with a Z or Y. Enter a table name, select the Tables radio button and then Click on Create button. Enter a Short description of the table in the Short Text area Select the delivery class.

Allowed check box Enter a field name. Enter the Data Element Name. Double click on the Data Element name. If the data element is not existing in the dictionary then you will get a Create Data Element pop up. If the data element is existing then you will be taken to the data element information screen in display mode and when you come back by pressing the BACK icon you will find the field type length and other information filled.

How to creating foreign keys in SAP Table

Click on the enter button if you want to create a new data element Enter the description of the data element. You can also change the docu status with transaction SE You can also enter documentation for the data element.

primary key and foreign relationship in sap abap tutorial

The text that you enter here will be displayed when you press F1 on the field. Click on the Yes button Enter the description for the domain in the Short text area Specify the data type in the Data Type box in the Format area Specify the field length Click on Save icon. In the resulting popup screen specify a Development Class. Activate the domain in the dictionary by clicking on the Generate icon on the application toolbar. Click on the BACK icon. You will get a popup screen Specify a Development Class to save the object.

The following data classes are available: Data in the tables of this class are not frequently changed Enter the Size Category. The Size Category defines the expected memory space required by the table on the database. You have 0 to 4 size category to choose from for your tables. It defines the size of the table extents. Enter 1 in the Size Category.

The value 1 in the size category indicates that the table is small. The above parameter can have the following values: This parameter defined whether the all clients or selected clients should be logged. Specify at least one of the fields as the primary key and then click on Save icon to save the table and click on Generate icon to activate the table.

To create more fields in the table, click on the New Fields button on the application toolbar and repeat the above steps. This is how you can create a table. You can use the existing data elements by placing the cursor in the data element box and then pressing the F4 key.

You can also reuse the domains that you create. You can also create Data Elements with the existing domains. However, a structure does not correspond to an object in the database. The runtime object nametab collects this information in a table in a form, which is optional for application program access.

In addition, it contains information about the table fields field name, position of the field in the table, data type, length, decimal places, reference field, check table, conversion routine, and so on. The index ID may contain only letters and figures. The ID '0' is reserved for the primary index. Table names with fewer than 10 places are filled with underscores with the ID being added on at the end.

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The index ID is thus always located at positions This data exists in this copy in sorted form. This sorting enables fast access to the data records of the table. In order that the remaining fields can also be read, that is, those fields not contained in the index, a pointer to the associated record of the actual table are included in the index. The operations, which the database utility executes for an object, are logged.

The object log can be displayed from the database utility. In other words Views are a logical datasets which contain data extracted from a single table or multiple tables as a single entity. The join conditions for database views can be formulated using equality relationships between any base fields.

The join conditions for the other view types must be obtained from existing foreign keys. Tables therefore can only be combined into a maintenance view or help view if they are linked to one another with foreign keys.

They are provided for the user as virtual tables.