Explain Query

[ueon]

I hired someone to do a project, and I need to alter his query a bit but have no idea what it says :

 

$query = "select a.*,b.Username,b.EmailAddress,b.UserID from status a inner join users b on(a.email=b.EmailAddress)  where a.email in($searchuser) order by id desc ";

 

 

[AyKay47]

query selects every field from table a.. which is what a.* means

the fields Username,EmailAddress,UserID from table b..

now the programmer aliases table status to be "a" and users to be "b", for a shorter query..

the tables are joined on the condition that the email field from the "status" table equals the Emailaddress field from table "users"

now the main query has a WHERE clause here it will grab rows where the value from field "email" from table "status" is in the array $searchuser..

it orders the results by id descending..

[ueon]

thanks aykay, but what does the ON and IN mean?

[AyKay47]

the ON is used in JOIN queries... and specifies how the two queries are joined, what the conditions need to be in order for the tables to join.. IN is a MYSQL function that searches an array of values for the specified value... documentation and examples can be found at these two links

 

http://dev.mysql.com/doc/refman/5.0/en/join.html

 

http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_in