Informatics Practices
Assertion. The PRIMARY KEY and FOREIGN KEY constraints are similar.
Reason. The FOREIGN KEY constraint links a column of a table with the PRIMARY KEY constraint of another table.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
SQL Queries
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Answer
Both A and R are true but R is not the correct explanation of A.
Explanation
The PRIMARY KEY and FOREIGN KEY constraints are similar in that they both deal with unique identifiers. However, they serve different purposes, PRIMARY KEY uniquely identifies each record in a table while FOREIGN KEY establishes a relationship between two tables by linking a column (or set of columns) to the PRIMARY KEY of another table.
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Related Questions
Assertion. The PRIMARY KEY can be defined only once in the CREATE TABLE command.
Reason. If the PRIMARY KEY is a composite key, then it is not defined with the individual columns but at the end of the table definition as a table constraint.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion. INSERT, UPDATE, DELETE, SELECT are the DML commands.
Reason. The DML commands manipulate the data stored in the database tables.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion. Data types varchar and char are the same as they both represent the string data.
Reason. The VARCHAR datatype stores variable string length while CHAR datatype stores the string always as fixed length strings.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
How are SQL commands classified ?