sql - converting a sub query into self join -


i have query in want find other authors each title in author mr.x

the query wrote is:

select distinct (author_name) authors      table1      title = (select title table1 (author_name) = 'x');

i got error: more 1 row returned subquery used expression

i think avoid error should use self join i'm not able figure out how it.

your subquery returning more 1 record , in such case can't use = operator rather should use in operator check against multiple values below 

where title in (select title table1 (author_name) = 'x')

so, query should like

select distinct (author_name) authors      table1      title in (select title table1 (author_name) = 'x');

to change join instead

select distinct (t1.author_name) authors      table1 t1     join table1 t2     on t1.title = t2.title

Comments

Post a Comment

Popular posts from this blog

Why can rails not find a route created by a helper? -

i created member route in rails 4: resources :line_items post 'decrement', on: :member end and gave matching method in line_items controller: def decrement @cart = current_cart @line_item = @cart.line_items.find_by_id(params[:id]) @line_item.decrement_quantity respond_to |format| if @line_item.save format.html { redirect_to shop_path, notice: 'line item updated.' } format.js {@current_item = @line_item} format.json { head :ok } else format.html { render action: "edit" } format.js {@current_item = @line_item} format.json { render json: @line_item.errors, status: :unprocessable_entity } end end end but when try make button: <%= button_to 'x', decrement_line_item_path(item) %> i error: no route matches [post] "/carts/25" what gives? your error message is: no route matches [post] "/carts/25" but expectin...
Read more

javascript - jquery or ashx not working -

i using ajax file upload control. it creating html: <form action="/pages/handlers/asyncfileuploadhandler.ashx" method="post" enctype="multipart/form-data" target="ajaxuploader-iframe-1397144545"> <input type="hidden" name="type" value="mindvoice"> <input type="file" id="imagefile" style="display: block; width: 80%; margin-right: auto; margin-left: auto;"> </form> and target is: <iframe width="0" height="0" style="display:none;" name="ajaxuploader-iframe-1397144545" id="ajaxuploader-iframe-1397144545"></iframe> the form submitted using .submit() . my ashx handler: <%@ webhandler language="c#" class="asyncfileuploadhandler" %> using system; using system.web; using nettpals.core; public class asyncfileuploadhandler : ihttphandler { public void processre...
Read more

opencv - DataType<cv::detail::deriv_type>::depth what is it used for -

i wondering why line used in lucas kanade tracker in opencv: datatype<cv::detail::deriv_type>::depth can explain me? in opencv, depth of mat refers type of data contained in mat 's data buffer. represented integer values correspond given data type. these integers commonly abstracted appropriate macro definition (e.g. uchar data represented macro cv_8u ). cv::datatype type-traits class provides method obtain corresponding integer value without having memorize macro means data type. there few cases user code needs use datatype::depth . more common datatype::type . a simple example shows 1 possible use of datatype::depth : cv::mat uchar_data = cv::mat::ones(3, 3, cv_8uc1); cv::mat float_data; uchar_data.convertto(float_data, cv::datatype<float>::depth); // ^^ equivalently replaced // cv_32f macro float_data.at<float>(0,1) += 0.5f; std::cout << float_data << std::endl;...
Read more