[SOLVED] Help me understand what these codes mean.

[Scorptique]

Hey all, I need help understand the codes. This set of codes work, they basically display the upcoming birthdays from my contact list.

 

$sql = "select cl_id, cl_fname, cl_lname, cl_email, date_format(cl_dob, '%d %b %Y') AS cl_dob,
(TO_DAYS((cl_dob + INTERVAL (YEAR(CURRENT_DATE)-YEAR(cl_dob) + (RIGHT(CURRENT_DATE,5)>
RIGHT(cl_dob,5))) YEAR)) - TO_DAYS(CURRENT_DATE)) as daysAway from contact_list where
username = '$username' order by daysAway DESC";

 

But...i dont really understand (TO_DAYS((cl_dob + INTERVAL (YEAR(CURRENT_DATE)-YEAR(cl_dob) + (RIGHT(CURRENT_DATE,5)>RIGHT(cl_dob,5))) YEAR)) - TO_DAYS(CURRENT_DATE)). if you understand, can you explain to me please? Thanks! ^^;;

[Mchl]

They're all explained here

If you have specific questions about any one function, ask.

[Scorptique]

Hm, I understand the individual functions, but I can't seem to comprehend how it works as a whole...especially for this part.

 

(TO_DAYS((cl_dob + INTERVAL (YEAR(CURRENT_DATE)-YEAR(cl_dob) + (RIGHT(CURRENT_DATE,5)>
RIGHT(cl_dob,5))) YEAR)) - TO_DAYS(CURRENT_DATE))

[Mchl]

So let's take it from outside to inside

 

If you drop outermost parentheses (), you will see, that there are two TO_DAYS() functions

 

TO_DAYS((cl_dob....)  -  TO_DAYS(CURRENT_DATE)

 

So, we have a number of days since year 0 calculated for the some date in the first function, and then number of days since year 0 for today substracted from it.

So basically it is a number of days between tha date in first function, and today.

 

Let's go some deeper into this first TO_DAYS() function

 

cl_dob + INTERVAL (YEAR(CURRENT_DATE)-YEAR(cl_dob) + (RIGHT(CURRENT_DATE,5)>RIGHT(cl_dob,5))) YEAR

 

So we now have two expressions added together.

 

cl_dob

This comes from table

 

INTERVAL (YEAR(CURRENT_DATE)-YEAR(cl_dob) + (RIGHT(CURRENT_DATE,5)>RIGHT(cl_dob,5)))

 

This one is strange, because INTERVAL() should have at least two arguments... you sure this is right?

[Scorptique]

o. I really dont know =/ And i found out that the codes aren't working right.... =( But I did copy that complicated section exactly from the example codes.

[Mchl]

Well... It should not be working. I just tested and INTERVAL() throws an error, when only one argument is passed.

[Scorptique]

Oh man, sorry to take up your time. Now I need to post another post to ask how to create a statement that works D=

[Mchl]

No problem.

If you need to understand such statements, do it as we started doing it here.

 

Try to find out, what is on the outside, and then go deeper and deeper inside.