outer-join

问题 I have two tables, say, price (5 rows, 1 column) and pricedate (6 rows, 1 column), they don't have anything in common. I want to obtain full outer join, so that my new table ABC has 30 rows, basically, every row in pricedate has all prices. How to do that? Can I use full outer join or something else? 回答1: My answer covers two cases: P (prices) and PD (pricedates) are tables P (prices) and PD (pricedates) are arrays Here is the code: % generate some sample data price = [1;2;3;4;5]; pricedate1

问题 Following this post, I still have an issue when I apply the answer given by @Vao Tsun to a bigger dataset made this time of 4 tables instead of 2 tables in the related post mentionned above. Here are my datasets: -- Table 'brcht' (empty) insee | annee | nb -------+--------+----- -- Table 'cana' insee | annee | nb -------+--------+----- 036223 | 2017 | 1 086001 | 2016 | 2 -- Table 'font' (empty) insee | annee | nb -------+--------+----- -- Table 'nr' insee | annee | nb -------+--------+-----

问题 Consider the following three files with headers in the first row: file1: id name in1 1 jon 1 2 sue 1 file2: id name in2 2 sue 1 3 bob 1 file3: id name in3 2 sue 1 3 adam 1 I want to merge these files to get the following output, merged_files: id name in1 in2 in3 1 jon 1 0 0 2 sue 1 1 1 3 bob 0 1 0 3 adam 0 0 1 This request has several special features that I have not found implemented in a handy way in grep/sed/awk/join etc. Edit: You may assume, for simplicity, that the three files have

问题 Code: outerMethod { @Override public void run() { innerMethod throws IOException } } Method that exceuted in thread throws checked exception - IOException. I need to handle this exception in main thread. Like: outerMethod() throws IOException { @Override public void run() { innerMethod() throws IOException } } Is this possible? If no, what would be a better way to do this? Thanks. 回答1: Use FutureTask http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/FutureTask.html#get%28%29 . It

问题 This question already has answers here : Closed 8 years ago . Possible Duplicates: Oracle “(+)” Operator Oracle (Old?) Joins - A tool/script for conversion? I have been somewhat spoiled by using Oracle for years. Now I am using mysql and cannot find a non-ansi version/shorthand version of outer joins in MySQL. In oracle I could do this select a.country acountry, a.stateProvince aStateProvince, b.countryName bcountry, b.name bstateProvince from User a, stateprovince b where a.country*=b

问题 Today when playing around with dynamic query generation I discovered that mysql has a hard maximum limit of how many tables can be used in a join: 61. This lead me to wonder about PostgreSQL, does PostgreSQL have a analogous limit? Note: I am asking this out of curiosity, not need. 回答1: There is no limit AFAIK. The query optimizer will switch to a different algorithm once a (configurable) limit of tables has been exceeded.But that just means the plan is calculated in a different way, not that

问题 I know there is really no difference, but is 'LEFT JOIN' an ANSI form or are there any RDBMS's that will fail 'LEFT JOIN' and require 'LEFT OUTER JOIN'. [I am asking here so I can save a few clicks, form fillings, etc to get the correct ANSI standard!] 回答1: [OUTER] is optional, per the ANSI spec (92, but I'm sure later versions also cover it). Of course, you're assuming that every SQL product is ANSI compatible. For joins, they probably are.. 回答2: ANSI JOINS http://www.oratechinfo.co.uk/ansi

问题 The following two sentences: hello there bye! are represented in the table sentence_words by: WORD_ID SENTENCE_ID WORD WORD_NUMBER 10 1 hello 1 11 1 there 2 12 2 bye! 1 I want to do an outer join query that gives me the results: WORD1 WORD2 hello there bye! NULL Note that I may want to start in the middle of the sentence so I cannot assume that word2 has word_number = 2. If I choose my_start_number = 2 then the query should give me: WORD1 WORD2 there NULL I tried: (my_start_number = 1) select

问题 Is an outer join only used for analysis by the developer? I'm having trouble finding a use case for why you would want to include data in two or more tables that is unrelated or does not "match" your select criteria. 回答1: An example use case would be to produce a report that shows ALL customers and their purchases. That is, show even customers who have not purchased anything. If you do an ordinary join of customers and purchases, the report would show only those customers with at least one

问题 What is the best way to do component-wise matrix addition if the number of matrices to be summed is not known in advance? More generally, is there a good way to perform matrix (or multi-dimensional array) operations in the context of data.table? I use data.table for its efficiency at sorting and grouping data by several fixed variables, or categories, each comprising a different number of observations. For example: Find the outer product of vector components given in each observation (row) of