D. (chart elemments) - correct answer
Explanation:
Both Primary Key and Candidate Key are the attributes that are used to access tuples from a table. These (Primary key and Candidate key) are also can be used to create a relationship between two tables.
- A Candidate Key can be any column or a combination of columns that can qualify as a unique key in the database. Each Candidate Key can qualify as a Primary Key.
- A Primary Key is a column or a combination of columns that uniquely identify a record. The primary key is a minimal super key, so there is one and only one primary key in any relationship.
<em> The main difference between them is that a primary key is unique but there can be many candidate keys. </em>
I hope you find this information useful and interesting! Good luck!
Answer:
Following is the expression written in "Bash script" (mixture of commands):
^\d{5}(?:[-\s]\d{4})?$
Explanation:
- ^ = For staring string (denotation).
- \d{5} = Matching 5 digits (first five unknown x's)
- (?:…) = Making Group (making group of former 5 digits)
- [-\s] = Match a hyphen or a space
(checking if a hyphen is present?)
- \d{4} = Matching 4 digits (next four unknown x's)
- …? = Pattern before it is optional
- $ = Ending of the string.(denotation)
Answer: TRUE
Explanation: Composite is simply used to refer to the existence of more than one event or pattern. The composite primary key as related to database management query refers to the synergy or combination of more than one field or column of a specified table which is used in sorting or accurate identification of a record. When attributes are combined, that is more than one, it assists in narrowing down the returned records such that records which are close and exclusive to the options specified are returned. Usually, the more the number of columns which makes uo the case mpoaite keys, the more unique and well sorted our returned output is.
