mysql - Joining three tables such that extra matches are discarded? -


how can write query give results of 3 tables such there's 1 result per "line"?

the tables are:

t1 (id, name, ip)  t2 (id, date_joined)  t3 (id, address, date_modified)

the relations are: t1-t2 1:1, t1-t3 1:m - there can many address rows per id in t3.

what want listing of users fields above, if have address, want record 1 (bonus if latest 1 based on t3.date_modified).

so should end number of records in t1 (happens equal t2 in case) , no more.

i tried:

select t.id, t.name, t.ip, tt.id, tt.date_joined, ttt.id, ttt.address  t1 t join t2 tt on (t.id = tt.id) join t3 ttt on (t.id = ttt.id)

and every sensible combination of left, right, inner, etc joins think of! keep getting multiple duplicate because of t3

this query should work:

select      t1.id, t1.name, t1.ip, t2.date_joined, t3x.address t1 join t2 on t1.id = t2.id left join (     select t3.*      t3      join (        select id, max(date_modified) max_date         t3         group id     ) max_t3 on t3.id = max_t3.id , t3.date_modified = max_t3.max_date ) t3x on t1.id = t3x.id

first normal join between t1 , t2 , left join derived table (t3x) set of t3 rows having latest date.


-

Comments

Post a Comment

Popular posts from this blog

OpenCV OpenCL: Convert Mat to Bitmap in JNI Layer for Android -

there several posts converting mat bitmap using utils.mattobitmap() function. i'm assuming function can called in java layer after importing utils class. i want transfer data memory address pointed uint32_t* bmpcontent; in code below. jniexport void jnicall java_com_nod_nodcv_nodcvactivity_runfilter( jnienv *env, jclass clazz, jobject outbmp, jbytearray indata, jint width, jint height, jint choice, jint filter) { int outsz = width*height; int insz = outsz + outsz/2; androidbitmapinfo bmpinfo; if (androidbitmap_getinfo(env, outbmp, &bmpinfo) < 0) { throwjavaexception(env,"gaussianblur","error retrieving bitmap meta data"); return; } if (bmpinfo.format != android_bitmap_format_rgba_8888) { throwjavaexception(env,"gaussianblur","expecting rgba_8888 format"); return; } uint32_t* bmpcontent; if (androidbitmap_lockpixels(env, outbmp,(void**)&bmpcontent)...
Read more

android - org.xmlpull.v1.XmlPullParserException: expected: START_TAG {http://schemas.xmlsoap.org/soap/envelope/}Envelope -

i trying hit soap api in application login purpose , getting above mentioned error , can 1 tell me going wrong , first time soap apis. here code hit soap :- vector<object> args = new vector<object>(); hashtable<string, object> hashtable = new hashtable<string, object>(); hashtable.put("email", "mss.siddhart28@gmail.com"); hashtable.put("password", "siddharth"); args.add(hashtable); soapserializationenvelope envelope = new soapserializationenvelope( soapenvelope.ver11); envelope.dotnet = true; envelope.xsd = soapserializationenvelope.xsd; envelope.enc = soapserializationenvelope.enc; (new marshalhashtable()).register(envelope); httptransportse androidhttptransport = new httptransportse( "http://tempuri.org/", 15000); androidhttptransport.debug = true; string result = ""; try { soapobject request = new soapobject("http:...
Read more

python - How to remove the Xframe Options header in django? -

i have made page has iframe . inside iframe want show multiple different links article facebook, or news, or youtube video or other possible url. but, due xframe header, unable so. referred following link: https://docs.djangoproject.com/en/1.8/ref/clickjacking/ , django xframeoptionsmiddleware (x-frame-options) - allow iframe client ip but didn't help. my settings.py file's middleware_classes is: middleware_classes = ( 'django.contrib.sessions.middleware.sessionmiddleware', 'django.middleware.common.commonmiddleware', 'django.middleware.csrf.csrfviewmiddleware', 'django.contrib.auth.middleware.authenticationmiddleware', 'django.contrib.auth.middleware.sessionauthenticationmiddleware', 'django.contrib.messages.middleware.messagemiddleware', 'django.middleware.clickjacking.xframeoptionsmiddleware', ) from http://django-secure.readthedocs.org/en/latest/middleware.html , found using ...
Read more