union | 易学教程

Complicated Query + Pagination Script

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问题 Problem 1: Pagination on my script is not working. After 20 entries, it only shows the most recent 20 entries and doesn't split them into different pages. Code is below: Problem 2: I am using the same pagination script for something else and over there it splits correctly but on the next page it shows the same results from page 1. I am using the same script except for the second script the: $query = "SELECT COUNT(*) as num FROM table where id = '$uid' ORDER BY id DESC"; and the SQL for that

Union of dataframes in R by rownames

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问题 I have 4 dataframes, each the index in a list. I would like to combine them altogether as one dataframe. In set language from mathematics, it would make most sense for this to be the union on the rownames. So I might have something like this: U <- union(dfSub[[1]], dfSub[[2]], dfSub[[3]], dfSub[[4]]) The problem with the union function is that it operates only on vectors. How can I get this to work on dataframes? How can I translate this into R? Is there a better way of achieving the desired

C Brexit

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C Brexit C Brexit 题意：有C个国家，P条贸易关系，X是你所在的国家，L是第一个离开的国家，如果一个国家有一半的贸易关系的国家离开，这个国家也离开。 A long time ago in a galaxy far, far away, there was a large interstellar trading union, consisting of many countries from all across the galaxy. Recently, one of the countries decided to leave the union. As a result, other countries are thinking about leaving too, as their participation in the union is no longer beneficial when their main trading partners are gone. You are a concerned citizen of country X, and you want to find out whether your country will remain in the union or not. You have crafted a list of

apply “ORDER BY” on a “UNION” (Mysql)

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问题 Good Day. So, everythign is in the title :) I am looking to merge the result of two requests and order the result together (as in not one after the other). => I was thinking of applying an union and order them. It didn't worked. I looked around like here on Stack or here developpez (!!french website). I try the different exemple, and suggestion, but no success. It seems from what i red that it's because I am working on Mysql. Anyway, here are my attemps, and the results: My original 2

Combine two SELECT queries in PostgreSQL

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问题 I would like to combine two select queries with UNION . How can I use the result from the first SELECT in the second SELECT ? (SELECT carto_id_key FROM table1 WHERE tag_id = 16) UNION (SELECT * FROM table2 WHERE carto_id_key = <the carto_id result from above> ) 回答1: Use a CTE to reuse the result from a subquery in more than one SELECT . You need PostgreSQL 8.4+ for that: WITH x AS (SELECT carto_id_key FROM table1 WHERE tag_id = 16) SELECT carto_id_key FROM x UNION ALL SELECT t2.some_other_id

union和union all的区别

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union和union all的区别 union和union all区别 union：对两个结果集进行并集操作，不包括重复行，同时进行默认规则的排序； union All：对两个结果集进行并集操作，包括重复行，不进行排序； https://www.cnblogs.com/mzhaox/p/11204767.html 来源： CSDN 作者：御剑归一链接： https://blog.csdn.net/wj1298250240/article/details/103860564

SQL - Invalid Identifier,, but where?

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问题 Im quite a beginner at SQL and I've been trying to workout for hours now what the problem is with this : select to_char(date_Created, 'MON DD YYYY') as jours, action, count(ID) from Logs group by action, to_char(date_Created, 'MON DD YYYY') union select distinct to_char(date_Created, 'MON DD YYYY'), action, 0 from Logs WHERE jours BETWEEN 'AVR. 14 2014' AND 'AVR. 15 2014' When I try it, it returns an error: ORA-00904: "JOURS" : identificateur non valide 00904. 00000 - "%s: invalid identifier"

SQL - Invalid Identifier,, but where?

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Running multiple queries in loop, and building multidimensional array

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问题 I'm building a stream of data based on users a user is following. While I have a working prototype, the code seems unnecessarily ugly with multiple loops with further queries nested in them. I was wondering if I could get any advice on simplifying this, possible handling more within the sql query itself? On with some code: (I've trimmed this down a little and removed some of the rows retrieved). $init = $conn->prepare("SELECT followerid FROM following WHERE userid=?"); $init->bind_param("s",

Running multiple queries in loop, and building multidimensional array

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