Need help understanding SQL Query.

[atrum]

Hello everyone,

 

I am working on a project that uses an sql query that is a little more advanced than what I have been exposed to in the past.

some

 

I understand most of it but it has some parts I don't really grasp.

Could any one break this down for me into parts and explain what it is this is doing?

SELECT c.* , (SELECT COUNT( * ) FROM `referrals` AS r WHERE r.`referrals_contact_id` = c.`contacts_id` ) AS gl_count FROM `contacts` AS c WHERE c.`contacts_demo_date` >= '" . $fromDateDB . "' AND c.`contacts_demo_date` <= '" . $toDateDB . "' AND `" . $_REQUEST['queryColumn'] . "` = " . $answer . ";

[teynon]

SELECT c.* , // Select all columns from contacts

 

// Count number of values in referrals

(SELECT COUNT( * ) FROM `referrals` AS r WHERE r.`referrals_contact_id` = c.`contacts_id` ) AS gl_count

 

// refer to table "contacts" as c

FROM `contacts` AS c

 

// Conditions for results for c.

WHERE c.`contacts_demo_date` >= '" . $fromDateDB . "' AND c.`contacts_demo_date` <= '" . $toDateDB . "' AND `" . $_REQUEST['queryColumn'] . "` = " . $answer . ";

[atrum]

Thanks for the reply teynon.

 

On that first part that says SELECT c.*

 

how is it that it knows that I want all columns from contacts when it seems c is assigned later in the query. Or like php does the order not matter?

[teynon]

It doesnt matter. How else could you define specific tables in the results?

 

* = wildcard / all

 

c.* = table referenced as c . all columns

[atrum]

Thanks man, appreciate the help.