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
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 |
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 |
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 |
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 Main Difference between ACCESS and SQL SERVER?
What is difference between materialized view and view?
What is a data source or ds? : sql server analysis services, ssas
Can we passed multiple recordset(set of records) using a Stored Procedure
What is normalization of database?
How to add more data to the testing table in ms sql server?
What is a mutating table error and how can you get around it?
How to populate a table in sql server?
What is a view?
How can u convert the Date to String?
Explain what is public role in sql server?
how to select 5 to 7 rows from a table, which contains 10 rows?
Oracle (3259)
SQL Server (4518)
MS Access (429)
MySQL (1402)
Postgre (483)
Sybase (267)
DB Architecture (141)
DB Administration (291)
DB Development (113)
SQL PLSQL (3330)
MongoDB (502)
IBM Informix (50)
Neo4j (82)
InfluxDB (0)
Apache CouchDB (44)
Firebird (5)
Database Management (1411)
Databases AllOther (288)