1. 1) What are the Differences between TRUNCATE and Delete?
S.N Truncate Delete
o
1 Truncate is faster Delete is comparatively slower
2 Removes all rows from a Can remove specific rows with
table Where clause
3 Is DDL Command Is DML Command
4 Resets identity of the table Does not reset identity of the
table
5 Removes the data by Removes one row at a time and
deallocating the data pages records an entry in the
and logs the deallocation. transaction log for each deleted
row.
6 Cannot be rolled back Can be rolled back
2) What are the differences between Primary key and Unique
key?
S.N Primary Key Unique Key
o
1 Creates Clustered index Creates Non-Clustered index
2 Null values are not allowed Allows only one null value
3) What are the Differences between Clustered Indexes and Non-
Clustered Indexes?
S.N Clustered Indexes Non-Clustered Indexes
o
1 It reorders the physical It sorts and maintain a separate
storage of records in the storage
table
2 There can be only one More than one
Clustered index per table
3 The leaf nodes contain data The leaf node contains pointer to
data
4) What are the differences between Stored Procedures and User
Defined Functions?
S.N Stored Procedures User Defined Functions
o
1 Stored Procedure cannot be User Defined Function can be
used in a Select statement used in a Select statement

2. 2 Stored procedure supports User Defined Function does not
Deferred Name Resolution support Deferred Name
Resolution
3 Stored Procedures are User Defined Functions are
generally used for generally used for Computations
performing Business Logic
4 Stored Procedure need not User Defined Functions should
return a value return a value
5 Stored Procedures can return User Defined Functions cannot
any datatype return Image
6 Stored Procedures can User Defined Functions accept
accept more number of input lesser number of input
parameters than User parameters than Stored
Defined Functions. Stored Procedures. UDF can have upto
Procedures can have upto 1023 input parameters
21000 input parameters
7 Stored Procedures can use Temporary Tables cannot be
Temporary Tables used in a User Defined Function
8 Stored Procedures can User Defined Functions cannot
execute Dynamic SQL execute Dynamic SQL
9 Stored Procedure supports User Defined Function does not
error handling support error handling.
RAISEERROR or @@ERROR are
not allowed in UDFs
10 Non-deterministic functions Non-deterministic functions
can be used in Stored cannot be used in User Defined
Procedures. Functions (UDFs). For example,
GETDATE() cannot be used in
User Defined Functions(UDFs)
5) What are the differences between Where and Having clauses?
S.N Where clause Having clause
o
1 It applies to individual rows It applies to a group as a whole
2 It selects rows before It selects rows after grouping
grouping
3 It cannot contain aggregate It can contain aggregate
functions functions
4 It can be used in select, It is used only in select clause
delete ,insert etc.
6) What are the differences between Union and UnionAll?
S.N Union UnionAll
o
1 This is used to eliminate It will not eliminate duplicate
duplicate rows rows

3. 2 This selects only distinct rows It selects all the values
3 It can be used to combine It can be used to combine
any number of queries maximum of 2 queries
4 It cannot contain aggregate It can contain aggregate
functions functions
7) What is the difference between normal Select statement and a
Cursor?
S.N Select statement Cursor
o
1 Select statements are used Cursors are used for row-level
for table-level processing processing