Question

Lets Say i have a table like this

WEB_LIST_TABLE

     KEY             Value
----------------------------------------
     134             google.com
     187             yahoo.com
     353             facebook.com

So on may be a million rows

The keys are primary keys and if i want to Select 50 Rows ,using the key, such as

Select * from WEB_LIST_TABLE where KEY in (134,187,...);

I m using where KEY in for selecting the rows, is it effective, based on performance ..?

Is there any other effective ways to do this?

Answer 1

This is effective, since field key is indexed. MySQL will use index to get the desired rows.

mysql>FLUSH STATUS;
mysql>SELECT * FROM WEB_LIST_TABLE WHERE KEY IN (134,187,192,241,10);
...
mysql>SHOW STATUS LIKE 'Handler_%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Handler_read_first         | 0     |
| Handler_read_key           | 5     |
| Handler_read_next          | 0     |
| Handler_read_prev          | 0     |
| Handler_read_rnd           | 0     |
| Handler_read_rnd_next      | 0     |
+----------------------------+-------+

As you can see, Handler_read_key is 5.

According to documentation this means that it read all the five rows based on key.