Question

I have an sql query:

DELETE **x**
FROM $table **x**
JOIN 
 ( SELECT vendors
        , email
        , MIN(lead_id) **min_lead_id** 
     FROM $table
    WHERE vendors = $vendor 
    GROUP BY vendors
           , email
 ) y 
ON **y**.vendors = **x**.vendors 
AND **y**.email = **x**.email
AND **y**.**min_lead_id** <> **x**.lead_id

I’m trying to understand it. I learned all the basics of sql. However the bolded variables(?)(x, y, min_lead_id) in the code sample boggles me. I have never encountered those and I dont know what google keywords I need to search for to get information. They dont show up in any of the sql documentation I have access to.

Can someone please point me in the right direction?

Answer 1

They are aliases for the tables and subqueries in your query.

• X is $table1
• Y is the subquery
• Min_Lead_ID is an alias (ie: a made up column name) for the result of MIN(lead_id)

It is optional to put an AS between the item and its alias to make this definition clearer