Sql “IN” is slower then simple `field_name`=“some”. Why?

Question

Why my MySQL query

SELECT ... WHERE `field_name`="some";

is processed faster then

SELECT ... WHERE `field_name` IN( "some" );

'IN' uses binary search, while the simple field_name ="some" uses the simple line-by-line searching. I am right, amn't I?

PS: it was tested in the table with < 100 lines. Maybe IN spends more time to "takeoff", but in big tables works faster?

Associated quastion, - does binary search applies either to IN values, or to lines in the table, or maby to both?

Answer 1

The IN statement in MySQL presumes an array of possible values that will be compared against every single row on the table/result set. While the WHERE clause uses single value comparison, uses indexes (if available) and mysql is optimizing the query in most of the cases.