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NOW(): yields the current date and time.
DATE(): extracts the date portion from a given date or datetime value.
MONTH(): yields the month component of a given date or datetime value as an integer (1 to 12).
MONTHNAME(): yields the name of the month for a given date or datetime value.
YEAR(): yields the year component of a given date or datetime value.
DAY(): yields the day of the month for a given date or datetime value.
DAYNAME(): yields the name of the weekday for a given date or datetime value.
Nested query: When an SQL query encloses another query, the outer query may use the result of the inner
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query.
BETWEEN operator checks whether a value is within a specified range. It may be applied to numbers, text,
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and dates.
IN operator checks whether a value is within a set.
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LIKE operator uses wildcard operators % and _ to define a pattern.
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GROUP BY clause: Used to output groupwise summary data.
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HAVING clause: Used to group the data so that the group as a whole satisfies a condition.
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Solved Exercise
A. Multiple Choice Questions
1. Which of the following is a feature of a Primary Key attribute?
a. uniqueness b. NOT NULL c. No repetition d. All of the above
2. Which of the following describes the degree of a relation?
a. Number of rows present in that relation.
b. Number of columns present in that relation.
c. Average number of rows in that relation
d. Count of numeric fields in a relation
3. Which non-primary attributes of a table refers to the primary key of another table?
a. Alternate Key
b. Foreign Key
c. Candidate Key
d. NOT NULL key
4. What does a NOT NULL constraint on an attribute in a table ensure?
a. That the attribute cannot have a NOT NULL value
b. That the attribute cannot have a NULL value
c. That the attribute cannot have zero value
d. That the attribute cannot have non-zero value.
5. The term Relation in an RDBMS denotes a __________.
a. Database b. Query c. File d. Table
6. Which math function is used to calculate the value of x raised to the power of y?
a. POWER(x, y) b. ROUND(x, y) c. MOD(x, y) d. UCASE(x)
Database Query using SQL 169

