mysql - get rows from two tables using join and sub query -


i have table of persons

person_id , person_name

another table of person_vehicle_relation

pv_id , person_id , vehicle_id, role

i want build query in can list of

pv_id , person_name

where vehicle_id= 3 , role = 'driver'.

i have tried join in following way not working. how can desired data?

select persons.person_name , person_vehicle_relation.pv_id  persons    inner join person_vehicle_relations on persons.person_id = (select person_id person_vehicle_relations vehicle_id = 3 , role= 'driver')

and error

msg 512, level 16, state 1, line 1 subquery returned more 1 value. not permitted when subquery follows =, !=, <, <= , >, >= or when subquery used expression.

why need subquery/inline view? simple should work.

select p.person_name , pvr.pv_id persons p inner join person_vehicle_relations  pvr    on p.person_id = prv.person_id pvr.vehicle_id = 3    , pvr.role= 'driver'

the reason why had error because subquery returned multiple persons , single person_id person's can't match multiple persons pvr.

you switch "in" instead of "=" , should work well; join , clause seemed simplest maintain , run.

one joins on pk/fk relationship applies limits in or in having. use subquery/inline views instead of straight join when need aggregation done , m-m relationship artificially inflate aggregation. may use subqueries in cross applies or in exists when don't need data second table. in case needed data both tables join seemed best.


Comments

Post a Comment

Popular posts from this blog

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m
Read more

javascript - Z-index in d3.js -

i have map , when hover effect on region of map below yellow line , circle, last ones disappear. how can solve problem? http://jsfiddle.net/ot21n9qx/ var arc = g.append("path") .style("fill", "none") .style("stroke", "yellow") .style("stroke-width", 2) .attr("d", "m" + pathorigin[0] + "," + pathorigin[1] + " q" + svgpoint[0] + "," + pathorigin[1] + " " + svgpoint[0] + "," + svgpoint[1]); var circlesize = d3.scale.linear() .domain([0, 0.5, 1]) .range([4, 10, 4]); svg not have z order draws objects in order created. need create path , circle after create highlight regions. here forked fiddle: http://jsfiddle.net/o00fzgaf/1/
Read more