what is the best way to tell if a row exists

[Mushroom]

For ex:
table T:
ID NAME SUBJECT
1 AAA EEE
2 BBB FFF

query "select count(*) from T where ID='1' limit 1" to tell if the row whose ID=1 exist.

what is the fastest query?
thanks!

[hand]

It's faster without using "limit".

The select
"select count(*) from T where ID='1'"
produces only one record, so it is not neccessary to limit 1 record to 1 record.

[Mushroom]

Are there any possibility to stop searching for the results when MYSQL detect an available result and we know that there are some rows conform to the condition.

[[deleted]]

count is not necessary at all if you are just looking for one record (the count wil ways be one or zero)

SELECT 1 FROM T WHERE id=1 LIMIT 1;

Yes, do use the LIMIT, because that will cause mysql to stop running the query as soon as it has found as many results as mentioned in the LIMIT, so LIMIT 1 will stop after finding one result;

Wether or not a row was found is stored in mysql_num_rows(), zero means no rows, one means one row.

Note: do not use this to prevent inserting duplicate, because that will not work.