What is the difference between count (1) selection of the tab and select count (*) tab;

What is the difference between count (1) selection of the tab and select count (*) tab;

994122 wrote:

Hello

SQL > set timing on

SQL > select count (*) of the emp

2 where deptno = 30;

COUNT (*)

---------------

6

Elapsed time: 00:00:00.01

SQL > select count (1) of the emp

2 * where deptno = 30

SQL > /.

COUNT (1)

-------------

6

Elapsed time: 00:00:00.01

See that both give the same time

Do you really think the 100th's of a second it takes 6 rows from counting will truly representative of the difference it takes actually?

Such a small data set cannot possibly show no difference to these larger units of time (in the calculation of terms where we have millions of instructions per second in lieu)

As the link to the FAQ provided in the response of Anton (first response on this thread) Watch, count (1) and count (*) are essentially the same, except that count (1) actually get re-written by the query re - write the step of the optimization to make it count (*).

Generally 'count (*)' makes more sense language, because it reads like "count" while "count (1)" reads as "count we ', which does not have as much good sense when you actually count all.

Tags: Database

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