difference between count(*) and count(Name)

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i want to count number of rows in a table for a particular ID.

Instead of writing SELECT COUNT(*) FROM TABLE shall i write SELECT COUNT(Name) FROM TABLE???

then tell me for better performance which is suitable??

Posted 15-Jan-13 20:03pm

sk. maqdoom ali

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kankeyan · Answer 1 · 2013-01-15T20:11:00

Solution 1

Instead of writing
Select count(*) from table
It will count null values and values

Select count(name) from table
It will count only the values present in Name column.

Second one is the better performance.

Posted 15-Jan-13 20:11pm

kankeyan

Anushkar · Answer 2 · 2013-01-15T20:14:00

Solution 2

Results can be vary according to the column values available in the relevant table.

COUNT(*) - retrieve the count of all the rows available in the table.
COUNT(Name) - retrieve only the count of non-null values available in the selected table.

Hope this will help you.

Posted 15-Jan-13 20:14pm

Anushkar

Prasad_Kulkarni · Answer 3 · 2013-01-15T20:22:00

Basically, if you do a COUNT(*), it returns an entire row of data and then counts it as 1, then goes to the next row and counts that as 2, and so on.

A COUNT(Name) would "count" a "Name" for row 1, a "Name" for row 2, and so on.

Anything you put in the COUNT() function work the same.

However, if you use a column name as the parameter, COUNT will return a count of NON-NULL values of that column.