select

问题 I have a mysql table with columns like this: `qid`, `category`, `question`, `choice_1`, `choice_2`, `choice_3`, `answer` In this table I have 2000 data and there are 7 different 'category'. I want to fetch 15 random rows from this table with equal number from each category. Since I have 7 categories, it's not possible to get equal number of rows from each category. In this case I can get 3 from one category. How can I achieve that with one query? I was thinking of getting 2 rows from each

问题 I have a mysql table with columns like this: `qid`, `category`, `question`, `choice_1`, `choice_2`, `choice_3`, `answer` In this table I have 2000 data and there are 7 different 'category'. I want to fetch 15 random rows from this table with equal number from each category. Since I have 7 categories, it's not possible to get equal number of rows from each category. In this case I can get 3 from one category. How can I achieve that with one query? I was thinking of getting 2 rows from each

问题 I have a mysql table with columns like this: `qid`, `category`, `question`, `choice_1`, `choice_2`, `choice_3`, `answer` In this table I have 2000 data and there are 7 different 'category'. I want to fetch 15 random rows from this table with equal number from each category. Since I have 7 categories, it's not possible to get equal number of rows from each category. In this case I can get 3 from one category. How can I achieve that with one query? I was thinking of getting 2 rows from each

问题 I have the following tables (with given columns): houses (id) users (id, house_id, active) custom_values (name, house_id, type) I want to get all the (distinct) houses and the count of associated users that: have at least 1 associated custom_value which name column contains the string 'red' (case insensitive) AND the custom_value column type value is 'mandatory'. have at least 100 associated users which status column is 'active' How can I run this query in PostgreSQL? Right now I have this

问题 I have a USERSEARCH table that should be used for fast substring searches for users. This feature is for an autocomplete search that occurs while someone is typing in a username or name. However, the query I am interested in will only show matches from users the subset of users the searcher follows. This is found in the USERRELATIONSHIP table. USERSEARCH ----------------------------------------------- user_id(FK) username_ngram name_ngram 1 "AleBoy leBoy eBoy..." "Ale le e" 2 "craze123

问题 This question already has answers here : Pandas filtering for multiple substrings in series (3 answers) Closed 2 years ago . I have a pandas dataframe which I want to check for substrings of a certain column. At the moment I have 30 lines of code of this kind: df['NAME'].str.upper().str.contains('LIMITED')) | (df['NAME'].str.upper().str.contains('INC')) | (df['NAME'].str.upper().str.contains('CORP')) They are all linked with an or condition and if any of them is true, the name is the name of

问题 i have a select field and a textarea one. And i am trying to hide/show the textarea in function of the select type i make: <select id="select" name="management"> <option value="0" selected="">Select One</option> <option value="1">Yes</option> <option value="0">No</option> </select> <textarea id="textarea" name="searching_gig_des" wrap="VIRTUAL" cols="50" rows="5"></textarea> ​ var textarea = $('textarea');. var select = $('#select').val(); textarea.hide(); if (select == '1'){ textarea.show();

问题 i have a select field and a textarea one. And i am trying to hide/show the textarea in function of the select type i make: <select id="select" name="management"> <option value="0" selected="">Select One</option> <option value="1">Yes</option> <option value="0">No</option> </select> <textarea id="textarea" name="searching_gig_des" wrap="VIRTUAL" cols="50" rows="5"></textarea> ​ var textarea = $('textarea');. var select = $('#select').val(); textarea.hide(); if (select == '1'){ textarea.show();

问题 i have a select field and a textarea one. And i am trying to hide/show the textarea in function of the select type i make: <select id="select" name="management"> <option value="0" selected="">Select One</option> <option value="1">Yes</option> <option value="0">No</option> </select> <textarea id="textarea" name="searching_gig_des" wrap="VIRTUAL" cols="50" rows="5"></textarea> ​ var textarea = $('textarea');. var select = $('#select').val(); textarea.hide(); if (select == '1'){ textarea.show();

问题 I know conditions are used in table joining. But I met a specific situation and the SQL codes writes like " Table A join table B ON TRUE " What will happen based on the "ON TRUE" condition? Is that just a total cross join without any condition selection? Actually, the original expression is like: Table A LEFT outer join table B on TRUE Let's say A has m rows and B has n rows. Is there any conflict between "left outer join" and "on true"? Because it seems "on true" results a cross join. From