Oracle SQL Oracle SQL SELECT Statements 2

Question 1

What does the DUAL table represent in Oracle SQL?

Accepted Answer

A special one-row, one-column table used for evaluating expressions

Answer

DUAL is a special Oracle table with one row and one column, used to evaluate expressions or call functions without referencing a real table.

Question 2

Which Oracle SQL clause is used to eliminate groups that don't meet a condition after GROUP BY?

Accepted Answer

HAVING

Answer

HAVING filters grouped rows based on aggregate conditions, while WHERE filters individual rows before grouping.

Question 3

What is the result of dividing a number by zero in Oracle SQL?

Accepted Answer

Raises an ORA-01476 error

Answer

Oracle raises ORA-01476 'divisor is equal to zero' error when a division by zero occurs in a query.

Question 4

In a SELECT statement, which order do clauses execute logically in Oracle SQL?

Accepted Answer

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY

Answer

Oracle processes clauses in this logical order: FROM, WHERE, GROUP BY, HAVING, SELECT, ORDER BY, even though SELECT is written first.

Question 5

Which Oracle SQL function returns the current date and time including seconds?

Accepted Answer

SYSDATE

Answer

SYSDATE returns the current date and time from the database server, including hours, minutes, and seconds.

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