13. What is Collation?
Collation refers to a set of rules that determine how data is sorted and compared. Character
data is sorted using rules that define the correct character sequence, with options for
specifying case sensitivity, accent marks, kana character types and character width.
14. What is Difference between Function and Stored Procedure?
UDF can be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section
where as Stored procedures cannot be. UDFs that return tables can be treated as another
rowset. This can be used in JOINs with other tables. Inline UDF's can be thought of as views
that take parameters and can be used in JOINs and other Rowset operations.
15. What is sub-query? Explain properties of sub-query?
Sub-queries are often referred to as sub-selects, as they allow a SELECT statement to be
executed arbitrarily within the body of another SQL statement. A sub-query is executed by
enclosing it in a set of parentheses. Sub-queries are generally used to return a single row as
an atomic value, though they may be used to compare values against multiple rows with the
A subquery is a SELECT statement that is nested within another T-SQL statement. A
subquery SELECT statement if executed independently of the T-SQL statement, in which it is
nested, will return a resultset. Meaning a subquery SELECT statement can standalone and is
not depended on the statement in which it is nested. A subquery SELECT statement can
return any number of values, and can be found in, the column list of a SELECT statement, a
FROM, GROUP BY, HAVING, and/or ORDER BY clauses of a T-SQL statement. A Subquery can
also be used as a parameter to a function call. Basically a subquery can be used anywhere
an expression can be used.
16. What are different Types of Join?
- Cross Join A cross join that does not have a WHERE clause produces the Cartesian product of the
tables involved in the join. The size of a Cartesian product result set is the number of rows
in the first table multiplied by the number of rows in the second table. The common
example is when company wants to combine each product with a pricing table to analyze
each product at each price.
- Inner Join A join that displays only the rows that have a match in both joined tables is known as inner
Join. This is the default type of join in the Query and View Designer.
- Outer Join A join that includes rows even if they do not have related rows in the joined table is an
Outer Join. You can create three different outer join to specify the unmatched rows to be
- Left Outer Join: In Left Outer Join all rows in the first-named table i.e. "left" table, which appears leftmost in the JOIN clause are included. Unmatched rows in the right
table do not appear.
- Right Outer Join: In Right Outer Join all rows in the second-named table i.e. "right" table, which appears rightmost in the JOIN clause are included. Unmatched rows in
the left table are not included.
- Full Outer Join: In Full Outer Join all rows in all joined tables are included, whether they are matched or not.
- Self Join This is a particular case when one table joins to itself, with one or two aliases to avoid
confusion. A self join can be of any type, as long as the joined tables are the same. A self
join is rather unique in that it involves a relationship with only one table. The common
example is when company has a hierarchal reporting structure whereby one member of
staff reports to another. Self Join can be Outer Join or Inner Join.
17. What are primary keys and foreign keys?
Primary keys are the unique identifiers for each row. They must contain unique values and
cannot be null. Due to their importance in relational databases, Primary keys are the most
fundamental of all keys and constraints. A table can have only one Primary key.
Foreign keys are both a method of ensuring data integrity and a manifestation of the
relationship between tables.
18. What is User Defined Functions? What kind of User-Defined Functions can be created?
User-Defined Functions allow defining its own T-SQL functions that can accept 0 or more
parameters and return a single scalar data value or a table data type.
Different Kinds of User-Defined Functions created are:
- Scalar User-Defined Function A Scalar user-defined function returns one of the scalar data types. Text, ntext, image and
timestamp data types are not supported. These are the type of user-defined functions that
most developers are used to in other programming languages. You pass in 0 to many
parameters and you get a return value.
- Inline Table-Value User-Defined Function An Inline Table-Value user-defined function returns a table data type and is an exceptional
alternative to a view as the user-defined function can pass parameters into a T-SQL select
command and in essence provide us with a parameterized, non-updateable view of the
- Multi-statement Table-Value User-Defined Function A Multi-Statement Table-Value user-defined function returns a table and is also an
exceptional alternative to a view as the function can support multiple T-SQL statements to
build the final result where the view is limited to a single SELECT statement. Also, the ability
to pass parameters into a TSQL select command or a group of them gives us the capability
to in essence create a parameterized, non-updateable view of the data in the underlying
tables. Within the create function command you must define the table structure that is
being returned. After creating this type of user-defined function, It can be used in the FROM
clause of a T-SQL command unlike the behavior found when using a stored procedure which
can also return record sets.