What is the difference between the following two sql
statements
select count(*) from <tablename>
select count(col_name) from <tablename>

Answers were Sorted based on User's Feedback



What is the difference between the following two sql statements select count(*) from <tablena..

Answer / debasis

select count(*) from <tablename> returns the number of rows
in the table.

select count(col_name) from <tablename> return number
values in the column (Ignores null value in the colum). For
example if we execute the following 2 queries then

select count(*) form emp
select count(comm) form emp

The result will be
14
4

Is This Answer Correct ?    34 Yes 7 No

What is the difference between the following two sql statements select count(*) from <tablena..

Answer / kushi

for the First Qry,result is "No.of records"
for the second Qry,result is "No.of records for particular
columnname"

Is This Answer Correct ?    17 Yes 0 No

What is the difference between the following two sql statements select count(*) from <tablena..

Answer / sandeep

select count(*) from <tablename>
- return number of records from table


select count(col_name) from <tablename>
- return number of records where col_name is NOT NULL
- Null value is eliminated by an aggregate or other SET
operation.

Is This Answer Correct ?    5 Yes 0 No

What is the difference between the following two sql statements select count(*) from <tablena..

Answer / sql2000

There seem to be a problem with the solutions provided by
the above.

Both the counts should provide the same result which is the
no of rows in the table.
count (*) will result in a bigger table scan than count
(col_name) hence its advisable to use count(1) while
calculating the count for a table.

Correct me if I am wrong...:)

Is This Answer Correct ?    1 Yes 3 No

What is the difference between the following two sql statements select count(*) from <tablena..

Answer / karthik

both will be display same record count.

Is This Answer Correct ?    2 Yes 12 No

Post New Answer

More SQL Server Interview Questions

What is the Disadvantage of indexed sequential file.

1 Answers   HCL,


How to create prepared statements using odbc_prepare()?

1 Answers  


How do you connect 100 files as a flat file sources in one package of SSIS?

2 Answers  


why does a sql statement work correctly outside of a user-defined function, but incorrectly inside it? : Sql server administration

1 Answers  


Security Question- SQL DBA exparts, need your help...

3 Answers  


What is tempdb in sql server?

1 Answers  


Explain the cursor lock types?

1 Answers  


Explain transaction isolation levels in sql server?

1 Answers  


Write a program using SQL queries to find a unique entry in a table.

1 Answers   Tech Mahindra,


What are user defined datatypes and when you should go for them?

1 Answers  


Define DML and DCL statements?

1 Answers   Hexaware, NIIT,


How to get a list of columns in a view using the "sp_help" stored procedure?

1 Answers  


Categories