How to select a row by a certain amount of similar data - mysql

Question

I'm about to build some sort of function or query where I can check if a certain record already exists in the database. The following rules apply:
The table has 6 columns
My yet-to-build-query has access to a complete row-object (all 6 values)
This query should find each row with at least 4 out of 6 corresponding values from the object I passed
Using MySQL
Is it even possible to build a query like this? My goal is to have a function which can return true if it's likely that a row like the passed object is already existing in the database.
Is my only option to make a query with multiple where-statements (where I try for each combination 4 different values)?
pseudo:
function getSimilarRow(Row_Object $row)
{
//select *
//from table_x
//where 4 out of 6 properties from object $row apply
}

Answer 1

You could use a case statement in the where clause for each property you are trying to match. If it meets the criteria then give the case statement a value of 1; if it doesn't then give it 0. The sum of the cases should then be >= 4.
I'm not that familiar with MySQL but the following will work (I knocked up a quick SQL Fiddle to show it working):
select * from SomeTable where
(case when propertyOne = 'value1' then 1 else 0 end) +
(case when propertyTwo = 'value2' then 1 else 0 end) +
(case when propertyThree = 'value3' then 1 else 0 end) +
(case when propertyFour = 'value4' then 1 else 0 end) +
(case when propertyFive = 'value5' then 1 else 0 end) +
(case when propertySix = 'value6' then 1 else 0 end) >= 4
Obviously you could change your logic in each clause if you'd prefer them to be likes or anything. You could even apply a weighting to each column by using something other than just 1 if you needed to get really creative.