sql - Nullify column in update if subquery returns empty -


i have following sql query

update container  set member_containers = members  ( select inter_container_membership.owning_container_id owner_cont       ,array_to_string(array_agg(inter_container_membership.member_container_id),',') members inter_container_membership  group inter_container_membership.owning_container_id) v container.id = owner_cont;

the problem is, if sub-query not return member_containers not updated, need set null if it's case, i've tried using exists clause didn't work.

update container  set member_containers =       case when exists (           select * inter_container_membership           container.id  = inter_container_membership.owning_container_id           ) members      else null end  ( select inter_container_membership.owning_container_id owner_cont       ,array_to_string(array_agg(inter_container_membership.member_container_id),',') members inter_container_membership  group inter_container_membership.owning_container_id) v container.id = owner_cont;

so thinking of nullifying out member_containers before updating it, not find way doing that.

to set column null in case subquery not find anything, could use correlated subquery instead of join:

update container c set    member_containers = (    select string_agg(member_container_id, ',')      inter_container_membership     i.owning_container_id = c.id    group  owning_container_id    );

often, kind of query wrong, because column shouldn't nullified if nothing found. seem want that.
also, correlated subqueries tend slow. consider add left join instead (doing same):

update container c set    member_containers = i.members   container c1 left   join (    select owning_container_id          ,string_agg(member_container_id, ',') members      inter_container_membership     group  1    ) on i.owning_container_id = c1.id c.id = c1.id;

also using string_agg() instead of array_to_string(array_agg(...)). needs postgres 9.0+.


Comments

Post a Comment

Popular posts from this blog

android - Get AccessToken using signpost OAuth without opening a browser (Two legged Oauth) -

i using signpost oauth access data magento server. have read various tutorials on same , reach point open browser user can enter credentials. however, per requirement have automate part. hence, user should not browser page. have set-up done on server side ( magento ), hit url , returned call page. same through program in android. i have tried below, consumer = new commonshttpoauthconsumer(key, secret); provider = new commonshttpoauthprovider(oauth_init_url,access_token_url, authorize_url); try { provider.retrieverequesttoken(consumer, oauth.out_of_band); log.d("tokens" , consumer.gettoken() + " -- " + consumer.gettokensecret()); } and request tokens. dont know how bypass next step. tried directly accessing accesstoken (stupid of me) provider.retrieveaccesstoken(consumer, "mycallback://callback"); no luck, ends in oauth.signpost.exception.oauthnotauthorizedexception: authorization failed (server replied 401). ...
Read more

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: mockito -

getting error org.mockito.exceptions.misusing.invaliduseofmatchersexception: invalid use of argument matchers! 1 matchers expected, 2 recorded. exception may occur if matchers combined raw values: //incorrect: somemethod(anyobject(), "raw string"); when using matchers, arguments have provided matchers. example: //correct: somemethod(anyobject(), eq("string matcher")); at when( getprogramservice .callservice(any(getprogramtype.class))) .thenreturn(jaxbresponse); please explain error , possible resolution the code posted looks fine; don't see problem it. code before or above causing exception. key here: invalid use of argument matchers! 1 matchers expected, 2 recorded. any , used above, doesn't return "special kind of null" or "special kind of getprogramtype"; don't exist. instead, returns null , side effect puts matcher on stack. whe...
Read more

google shop client API returns 400 bad request error while adding an item -

i'm working on solution add items in google shopping market java application. following tutorial real mess because of missing classes of laste release, after setting 1.5-beta maven managed make base example typecheck correctly classes. still can make simple task of adding 1 item. instead of posting whole code i'm posting part creates product feed. private product createproduct(string id) { product product = new product(); product.title = "red wool sweater"; product.content = new content( "text", "comfortable , soft, sweater keep warm on " + "cold winter nights. red , blue stripes."); product.appcontrol = new appcontrol(); product.appcontrol.addrequireddestination("productads"); product.externalid = id; product.lang = "it"; product.country = "it"; product.condition = "nuovo"; product.price = new price("eu...
Read more