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