concatenation

问题 I am trying to create simple requirements management database. Basically I have 2 tables like below: Contract_requirements with 2 columns: CR_ReqID | Description reqCR1 | Contract req description 1 reqCR2 | Contract req description 2 SW_requirements Title | SW_ReqID | RootReq SW req description 1| reqSW1 | reqCR1, reqCR2 SW req description 2| reqSW2 | reqCR1 SW req description 3| reqSW3 | reqCR2 And I would like to write query to receive such a table: CR_ReqID |Description |where used? reqCR1

问题 I would like to take a data frame with characters and numbers, and concatenate all of the elements of the each row into a single string, which would be stored as a single element in a vector. As an example, I make a data frame of letters and numbers, and then I would like to concatenate the first row via the paste function, and hopefully return the value "A1" df <- data.frame(letters = LETTERS[1:5], numbers = 1:5) df ## letters numbers ## 1 A 1 ## 2 B 2 ## 3 C 3 ## 4 D 4 ## 5 E 5 paste(df[1,]

问题 This question already has answers here : What do ellipsis […] mean in a list? (6 answers) Closed 3 years ago . EDIT: I was careless in my original examples. The behaviour occurs not when I add list A to itself, but rather when I add a list containing list A to A itself. Please see the corrected examples below. I am trying to understand how ellipsis lists (those lists that appear as [...] and occur when you have a list references itself) works in Python 2. In particular, I want to know why, if

问题 I would like to append a byte array to an already existing file (C:\test.exe) . Assume the following byte array: byte[] appendMe = new byte[ 1000 ] ; File.AppendAllBytes(@"C:\test.exe", appendMe); // Something like this - Yes, I know this method does not really exist. I would do this using File.WriteAllBytes, but I am going to be using an ENORMOUS byte array, and System.MemoryOverload exception is constantly being thrown. So, I will most likely have to split the large array up into pieces and

问题 How do you concatenate characters in java? Concatenating strings would only require a + between the strings, but concatenating chars using + will change the value of the char into ascii and hence giving a numerical output. I want to do System.out.println(char1+char2+char3... and create a String word like this. I could do System.out.print(char1); System.out.print(char2); System.out.print(char3); But, this will only get me the characters in 1 line. I need it as a string. Any help would be

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Combine rows in Access 2007 Access 2007 - Concatenate fields from one column in one table into a single, comma delmited value in another table Currently I have a table structure that is somewhat like this: Name --- Cat --- Desc --- Thresh --- Perc --- Err --- BP Bob -------C1-------Inf--------7Per--------0.05------0-----ADC2 Bob -------C1-------Inf--------7Per--------0.05------2-----BAC2 Bob -------C1-------Inf-

问题 I don't know concatenation operator for MySQL. I have tried this code for concatenation: SELECT vend_name || ' (' || vend_country || ')' FROM Vendors ORDER BY vend_name; But it didn't work. Which operator should I use to concatenate strings? 回答1: You were using ORACLE type of concatenation. MySQL's Should be SELECT CONCAT(vend_name, '(', vend_country, ')') Call the CONCAT() function and separate your values with commas. 回答2: || is the ANSI standard string concatenation operator, supported by

问题 I've recently learned how to join 2 arrays using the + operator in PHP. But consider this code... $array = array('Item 1'); $array += array('Item 2'); var_dump($array); Output is array(1) { [0]=> string(6) "Item 1" } Why does this not work? Skipping the shorthand and using $array = $array + array('Item 2') does not work either. Does it have something to do with the keys? 回答1: Both will have a key of 0 , and that method of combining the arrays will collapse duplicates. Try using array_merge()

问题 I need a similar function to Oracle WM_CONCAT in SQL Server, which returns a comma separated list of whatever field you pass it as argument. For example, in Oracle, select WM_CONCAT(first_name) from employee where state='CA' returns "John, Jim, Bob". How can I do this in SQL Server? Thanks 回答1: The actual answer: SELECT SUBSTRING(buzz, 2, 2000000000) FROM ( SELECT firstname FROM employee WHERE State = 'CA' FOR XML PATH (',') ) fizz(buzz) A common question here. Some searches: FOR XML PATH

问题 I am reading Accelerated C++ by Koenig. He writes that "the new idea is that we can use + to concatenate a string and a string literal - or, for that matter, two strings (but not two string literals). Fine, this makes sense I suppose. Now onto two separate exercises meant to illuminate this . Are the following definitions valid? const string hello = "Hello"; const string message = hello + ",world" + "!"; Now, I tried to execute the above and it worked! So I was happy. Then I tried to do the