Trouble in MySQL querying -


i developing digital mobile loyalty app , have face problem in querying mysql code...

i have 4 tables: customer, card, redemption, merchant

currently trying want system first check if customer possess loyalty card of merchant when making redemption

  • if yes, can proceed
  • if no, system create card them , proceed

the redemption code generated merchant...

the problem how should query code so?

customer   - customer_id  - c_email  - c_password  - c_name  card   - card_id  - chop_amt  - customer_id*  - merchant_id*  merchant   - merchant_id  - merchant_name  redemption   - red_id  - red_code  - card_id*  - merchant_id*

i tried writing code own now...can some1 please me check?

select *  customer customer  join card card    on customer.customer_id = card.customer_id  join redemption redemption    on card.merchant_id = redemption.merchant_id  card.merchant_id = redemption.merchant_id ,       redemption.red_code = 'a002'

i recommend putting unique index on card table merchant / customer entries. if go approach, can insert ... on duplicate key update id = id. ensure record exists regardless.

to create index, this

create unique index customer_merchant on card (customer_id, merchant_id);

now have in place, go ahead , insert, not insert new row if 1 exists

insert card (chop_amt, customer_id, merchant_id) values(0.00, 1, 1) on duplicate key update card_id = card_id

the update card_id = card_id part alias "don't anything", it's setting card_id itself


Comments

Post a Comment

Popular posts from this blog

SPSS keyboard combination alters encoding -

my question not have programming practical issue on spss. accident keyword combination cannot remember because did not intend press changed encoding in spss , text in data in different language english shown small boxes. nevertheless, when kind of analysis performed different language text shown in output. does know reason? tried change encoding did not produce result. first, @ edit > options , see whether setting unicode or locale. might fix it. if have text in multiple languages, want unicode. otherwise, may have specific locale set wrong. can change set locale, need know locale want use.
Read more

Add new record to the table by click on the button in Microsoft Access -

in ms access form want implement separate button, adds new record table. in order added button , attached button event: private sub btnaddrec_click() refresh codecontextobject on error resume next docmd.gotorecord , , acnewrec if err.number <> 0 btnaddrec.enabled = false end if end end sub everything ok when open window , click btnaddrec button, problem when first of perform navigation through existed records , after click on button. got runtime error: 2105: «you can't go specified record. may @ end of recordset» . how solve issue, need have ability add new record on click on specific button, no matter, have walked or not walked through records before. thanks. i created simple form field call description (and autonumber) , created button code follows click event. filled number of records , navigated through them, clicked addnewrec button. form navigated new record without issues. able click addnewrec button directly after
Read more

javascript - jQuery .height() return 0 when visible but non-0 when hidden -

i have problem here right opposite others: in jquery cannot height of element when it's visible, when hidden. have html code: <div id="filtering-filter-holder"> <div id="filtering-filter-holder-inner"></div> </div> basic css it: #filtering-filter-holder { display: none; position: absolute; width: 420px; min-height: 100px; padding: 5px 5px 5px 5px; background-color: #ffffff; border: 1px solid #164372; } and finally, js in document.ready(): $('div.filtering-filter-headline').mouseenter(function() { var el = $(this).parent().find('div.filtering-filter-content'); if ($('div#filtering-filter-holder').is(':visible')) { $('div#filtering-filter-holder-inner').stop(true, true).fadeout(300, function() { $('div#filtering-filter-holder-inner').html($(el).html()); var height = $('div#filtering-filter-holder-inner&#
Read more