mysql - Shared Primary Key -

-

i guess semi-common question can't find in list of past questions. have set of tables products need share primary key index. assume following:

product1_table:     id,     name,     category,     ...other fields  product2_table:     id,     name,     category,     ...other fields  product_to_category_table:     product_id,     category_id

clearly useful have shared index between 2 product tables. note, idea of keeping them separate because have largely different sets of fields beyond basics, share common categorization.

update:

a lot of people have suggested table inheritance (or gen-spec). option i'm aware of given in other database systems share sequence between tables hoping mysql had similar solution. shall assume doesn't based on responses. guess i'll have go table inheritance... thank all.

it's not common, no. there no native way share primary key. might in situation this:

product_table     id     name     category     general_fields...  product_type1_table:     id     product_id     product_type1_fields...  product_type2_table:     id     product_id     product_type2_fields...  product_to_category_table:     product_id     category_id

that is, there 1 master product table has entries products , has fields generalize between types, , type-specified tables foreign keys master product table, have type-specific data.


Comments

Post a Comment

Popular posts from this blog

java - SNMP4J General Variable Binding Error -

-
i trying use snmp4j snmp bulkget. when ever use snmp4j make call returned responseevent error says "general variable binding error" , data returned equal null. to debug: print out, console, exact oid , version number using in snmp4j. use printed out data snmpwalk on command line. valid results. know sending snmp4j correct pdu correct oid, version number, max repititions, etc. i have used snmp4j , code wrote succesffuly monitor other devices years. don't know different time. leaving me stumped. why "general variable binding error?" causes error? ideas debug? can reproduced? if so, first action should using wireshark or microsoft network monitor capture network packets. my guess agent gives generr response, not surprising, http://www.ietf.org/rfc/rfc1157.txt
Read more

windows - Python Service Installation - "Could not find PythonClass entry" -

-
i working on building python service. inducing error, not sure inducing it. ps c:\...> python .\file.py debug debugging service myservice - press ctrl+c stop. error 0xc00000f4 - not find service's pythonclass entry in registry error 1814 - specified resource name cannot found in image file. error 0xc0000080 - not locate module name in python class string (ie, no '.') this error coming pythonservicemessages.mc in pythonwin32. it turns out error result caused exception being thrown , python script dying off.
Read more

Determine if a XmlNode is empty or null in C#? -

-
the following code takes xmlnode data type , populates dataset object xmlnode content. write dataset's content file. public void populatedataset(xmlnode node) { xmlnodereader reader = new xmlnodereader(node); dataset ds = new dataset(); ds.readxml(reader); system.guid guid = system.guid.newguid(); string name = string.format("{0}{1}_{2}.xml", utility.xmloutputpath, utility.xmloutputfilename, guid.tostring()); //need write "node empty" file if xmlnode object empty of null ds.writexml(name, xmlwritemode.ignoreschema); } the problem encountered 1 scenario not write content file. how determine if xmlnode object null or empty? you can check if node parameter null or has innertext or innerxml properties null or empty, when enter method before creating xmlnodereader .
Read more