A. Primary Key is used when defining a Send Relationship B. Primary Key is the unique value to identify a subscriber C. Primary Key identifies a row or a field in a data extension as unique D. Primary Key prevents data from being overwritten in a data extension
Primary Key identifies a row or a field in a data extension as unique
NOTE: primary key determines whether the system considers this key to be the primary key of this table. The system requires that the value in this field be unique so it can use this field to uniquely identify a row. It speaks to the data schema for a particular table/data extension. Is only used for data extensions and is required when adding/updating fields.
Marmora_85: the answer says "identifies a row or a field".... Primary Keys idenitify a row as unique, never a field. Moreover defining a primary key in data extension allows importing with Add, Update, Add and Update instedo of only "Overwrite"!
Primary Key - If you select this checkbox, the system requires a UNIQUE VALUE for that field, so it can uniquely identify a ROW (not a field). If there is NO primary key in a table, you can only overwrite.
A primary key is something that can be used to make sure that the data that will be available in one specific column will be unique from all the other columns available. You can possibly set some restraints with the primary keys. With this meaning, I would have to go with C. The primary key can also be used as a unique identifier so that it will be easier to determine one type of data over another.
To give an example, a table may have different types of data, but one column will place all of the customer numbers of the various customers. This will be considered to be protected by the primary key because the data placed in that column will identify the various customers that are placed in the same data field.
C is the answer to this question. The primary key is responsible for making sure that the data in one specific column is unique. It is with the use of primary keys that you can make constraints.
For example, you may set a certain column with a foreign key. This makes that the whole column is being powered with the primary key. Null data is not allowed for primary keys. Let us say that the unique detail about a certain record is the fact that it has all of the license plates of the different vehicles within a certain area. This will be locked by the primary key because this data is not available elsewhere.