key

问题 Is it right to expect that, for the typical modern RDBMS, querying by one specific primary key is as fast as querying a hashtable by key? Or is there "actual work" done to traverse the table and track down the primary key value? That seems unthinkably wasteful, even if there are automatic indexes for primary keys. 回答1: Database operation involves access of secondary memory unit (Disk). And to achieve efficiency important is to reduce block access time(not operations). Complexity of Select

问题 How can I check if a chosen cipher algorithm transformation supports certain key length? boolean checkAlgorithm( String encryptMethod, int keyLength ) { Cipher cipher = Cipher.getInstance(encryptMethod); int maxLength = cipher.getMaxAllowedKeyLength(encryptMethod); if ( keyLength <= maxLength && SOMETHING_ELSE ) { return true; } else { return false; } } Is there a way without doing it one by one for each transformation like: switch( encryptMethod ) { case "Blowfish": if ( keyLength <=

问题 How can I check if a chosen cipher algorithm transformation supports certain key length? boolean checkAlgorithm( String encryptMethod, int keyLength ) { Cipher cipher = Cipher.getInstance(encryptMethod); int maxLength = cipher.getMaxAllowedKeyLength(encryptMethod); if ( keyLength <= maxLength && SOMETHING_ELSE ) { return true; } else { return false; } } Is there a way without doing it one by one for each transformation like: switch( encryptMethod ) { case "Blowfish": if ( keyLength <=

问题 How can I check if a chosen cipher algorithm transformation supports certain key length? boolean checkAlgorithm( String encryptMethod, int keyLength ) { Cipher cipher = Cipher.getInstance(encryptMethod); int maxLength = cipher.getMaxAllowedKeyLength(encryptMethod); if ( keyLength <= maxLength && SOMETHING_ELSE ) { return true; } else { return false; } } Is there a way without doing it one by one for each transformation like: switch( encryptMethod ) { case "Blowfish": if ( keyLength <=

问题 This question already has answers here : mysql two column primary key with auto-increment (4 answers) Closed 7 years ago . I'm trying to do the composite key with one of them auto incrementing, but when I try to enter a new row it just continue the sequential. Here's the example of what happens: Item_1 | Item_2 1 | 1 1 | 2 2 | 3 2 | 4 2 | 5 Here's the example of what I want: Item_1 | Item_2 1 | 1 1 | 2 2 | 1 2 | 2 2 | 3 I create the table this way: CREATE TABLE IF NOT EXISTS `usuarios` ( `cod

问题 This question already has answers here : mysql two column primary key with auto-increment (4 answers) Closed 7 years ago . I'm trying to do the composite key with one of them auto incrementing, but when I try to enter a new row it just continue the sequential. Here's the example of what happens: Item_1 | Item_2 1 | 1 1 | 2 2 | 3 2 | 4 2 | 5 Here's the example of what I want: Item_1 | Item_2 1 | 1 1 | 2 2 | 1 2 | 2 2 | 3 I create the table this way: CREATE TABLE IF NOT EXISTS `usuarios` ( `cod

问题 I'm trying to find key of object which is containing my value. There is my object: var obj = {} obj["post1"] = { "title": "title1", "subtitle": "subtitle1" } obj["post2"] = { "title": "title2", "subtitle": "subtitle2" } And now, I'm trying to get object key of value "title2" function obk (obj, val) { const key = Object.keys(obj).find(key => obj[key] === val); return key } console.log(obk(obj, "title2")) Output: undefined Desired output: post2 回答1: You have to access the subkey of the object:

问题 I'm having trouble at the bottom part where i am trying to set the sentinel exit key to quit.. im not sure exactly how i am supposed to do it. int number; do { Scanner Input = new Scanner(System.in); System.out.print("Enter a positive integer or q to quit program:"); number = Input.nextInt(); } while(number >= 0); do { Scanner Input = new Scanner(System.in); System.out.print("Input should be positve:"); number = Input.nextInt(); } while(number < 0); do { Scanner quit = new Scanner(System.in);

问题 I have a problem. I need write a C# program Input: Allows the user to enter multiple lines of text, press Ctrl + Enter to finish typing Output: Standardize by, rearranging lines in the right order of increasing time. I was tried but I don't know how to catch Ctrl + Enter from keyboard: I expect the output like Example: “Created at 28/02/2018 10:15:35 AM by Andy. Updated at 03/03/2018 02:45:10 PM by Mark Clear name at 02/03/2018 11:34:05 AM by Andy” DateTime is needed rearranging 回答1: You need

问题 Say I have the following JSON: { "a": 0, "b": "c", "d": { "e": { "f": "g", "comments": { "leading": "Lorem ipsum" }, "h": { "i": { "j": [ 1, 2 ] }, "comments": { "trailing": "dolor sit" } } }, "comments": { "leading": "amet." } } } I want to get an array with the values of all the fields named comments (which can be nested in any level). So, in this case I want to get: [ { "leading": "Lorem ipsum" }, { "trailing": "dolor sit" }, { "leading": "amet." } ] The order of the array doesn't matter.