Question

I have the following prepared query I am using with mysql and php. It is to allow users to be added to a particular category, passed in via $subcat.

$alterQuery = "UPDATE AUCTIONS SET subcat= ? WHERE article_no= ?";
   if ($altRecord = $con->prepare($alterQuery)) {
       $altRecord->bind_param("ss", $subcat, $pk);
       $altRecord->execute();
    $altRecord->close();
    echo "true";
    }

What I would like to do, in the same query, is insert a new record in the USERS table only inserting the username, after checking that the username does not already exist. Is it possible just to change $alterQuery to:

What is the best what to do this?

Check for the username, and if it == null, do a subsequent insert? can I have two different queries executed in the same if block?

edit: attaching database scheme in response to comment

AUCTIONS    

    ARTICLE_NO      varchar(20) primary key
    ARTICLE_NAME    varchar(100)
    SUBTITLE    varchar(20)
    CURRENT_BID     decimal(5,2)
    START_PRICE     decimal(5,2)
    BID_COUNT   varchar(20)
    QUANT_TOTAL     varchar(20)
    QUANT_SOLD  varchar(20)
    ACCESSSTARTS    varchar(30)
    ACCESSENDS  varchar(20)
    ACCESSORIGIN_END    varchar(20)
    USERNAME    varchar(20)     
    BEST_BIDDER_ID  varchar(20)     
    FINISHED    tinyint(4)  
    WATCH   tinyint(4)      
    BUYITNOW_PRICE  decimal(5,2)    
    PIC_URL     varchar(120)    
    PRIVATE_AUCTION     tinyint(4)
    AUCTION_TYPE    varchar(20)     
    ACCESSINSERT_DATE   varchar(20)
    ACCESSUPDATE_DATE   varchar(20)
    CAT_DESC    varchar(20)     
    CAT_PATH    varchar(20)     
    ARTICLE_DESC    text    
    COUNTRYCODE     varchar(20)
    LOCATION    varchar(20)
    CONDITIONS  varchar(20)
    REVISED     tinyint(4) 
    PAYPAL_ACCEPT   tinyint(4) 
    PRE_TERMINATED  tinyint(4) 
    SHIPPING_TO     varchar(20)
    FEE_INSERTION   decimal(5,2)
    FEE_FINAL   decimal(5,2)
    FEE_LISTING     decimal(5,2)
    PIC_XXL     tinyint(4) 
    PIC_DIASHOW     tinyint(4) 
    PIC_COUNT   varchar(20)
    ITEM_SITE_ID    varchar(20)
    STARTS  datetime    
    ENDS    datetime    
    ORIGIN_END  datetime
    SUBCAT  varchar(20)

USERS
    username    varchar(30) primary key
    firstname   varchar(30)
    lastname    varchar(30)
    flaggedauctions     varchar(30)
    lastauction     varchar(30)     
    street1     varchar(30)     
    city1   varchar(30)     
    postcode1   varchar(30)
    street2     varchar(30)
    city2   varchar(30)     
    postcode2   varchar(30)
    phone   varchar(30)     
    mobilephone     varchar(30) 
    fax     varchar(30)     
    email   varchar(30)     
    website     varchar(30) 
    bank    varchar(30)     
    banknumber  varchar(30)
    accountnumber   varchar(30)
    comments    varchar(30)

Answer 1

It will be best to create a stored procedure:

DELIMITER $$
CREATE PROCEDURE prc_add_user_to_category(_subcat VARCHAR(20), _article_no VARCHAR(20), _username VARCHAR(30))
BEGIN
        UPDATE  AUCTIONS
        SET     subcat= _subcat
        WHERE   article_no= _article_no;
        INSERT
        INTO    users (username)
        VALUES  (_username)
        ON DUPLICATE KEY
        UPDATE
        username = username;
END
$$
DELIMITER ;

and call it from your code:

$alterQuery = "CALL prc_add_user_to_category(?, ?, ?)";
   if ($altRecord = $con->prepare($alterQuery)) {
       $altRecord->bind_param("ss", $subcat, $pk, $userid);
       $altRecord->execute();
    $altRecord->close();
    echo "true";
    }

Checked and proved to compile and work against your schema on 5.2.0-falcon-alpha-community-nt-log