mysql - child tables and foreign keys -

-

i know there have been myriads of questions concerning primary , foreign keys. looking through them, cannot seem find simple answer question. understanding of primary , foreign keys foreign key column designated in child table refers primary key column in parent table. correct, or have backwards? if indeed correct, trying find out why having difficulty creating foreign key in child table such:

salesorders.sonumber (pk) < customer.sonumber (fk)

i using navicat mariadb (same mysql) , error is:

1452 - cannot add or update child row: foreign key constraint fails ('customer_orders','#sql7a8_3'; constraint 'sonumber' foreign key ('sonumber') references 'salesorder' ('sonumber') on delete no action on update cascade)

customer_orders database name. naming foreign key 'sonumber' same column name in child table (customer) , parent table (salesorders). incorrect? should give foreign key name?

gitpicker

the foreign key should have own unique name, yes. sonumber_fk or similar simple naming schema.

you need make sure every entry in foreign key column has corresponding entry in referenced table, otherwise not able create foreign key.


Comments

Post a Comment

Popular posts from this blog

javascript - how to protect a flash video from refresh？ -

-
<!doctype html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> <title>flash video refresh</title> </head> <body> <div id="playerzone"><embed height="496" width="580" flashvars="flvid=19742822&amp;createtime=2012-4-19 13:46:33" wmode="opaque" allowscriptaccess="always" allowfullscreen="true" quality="high" bgcolor="#000000" name="player" id="player" src="swf/mine.swf" type="application/x-shockwave-flash"></div> <a onclick="return test();" id="test">click me popup div,and hide scrollbar</a> </body> the code upon： for example,when click a#test button,popup div,it's no problem,but want hide scrollbar while div popup. i used $('html').css('overflow','hidden') in...
Read more

visual studio 2010 - Connect to informix database windows form application -

-
i trying figure out how connect ibm informix database. have been doing research , have found threads 5 years ago examples not working. i have installed latest sdk ibm informix. i have included ibm.data.informix.dll references in project. i have included using ibm.data.informix; i adding button , on click testing conenction. debug error "sql0035n file "c:\users\adam\documents\visual studio 2010\projects\test\test\msg\en_us\db2nmp.xml" cannot opened." this file not exist , dont see anywhere in program files (x86)\ibm informix client sdk directory. my on click code is private void button1_click(object sender, eventargs e) { const string host = "192.168.obfuscated"; const string servicenum = "1525"; //port? const string server = "serverobfuscated"; const string database = "dbobfuscatedy"; const string user = "myusername"; const string password = ...
Read more

android - Associate same looper with different threads -

-
Image
in application, want create multiple threads working on single queue. create queue know need call looper.prepare() . i want other threads create should associated looper created first thread, how can achieve this? use 1 of java thread safe queue class java.util.concurrent package instead of looper achieve goal. it's more common practice. share queue between threads , post task queue entry 1 thread can entry thread. blockingqueue can - in 1 thread call take() , block thread until thread put() entry queue. that's all. producer consumer pattern example blockingqueue or concurrentlinkedqueue about blockingqueue
Read more