Search Results

Search found 1908 results on 77 pages for 'relational operators'.

Page 7/77 | < Previous Page | 3 4 5 6 7 8 9 10 11 12 13 14  | Next Page >

• Designing persistence schema for BigTable on AppEngine

  - by Vitalij Zadneprovskij

  I have tried to design the datastore schema for a very small application. That schema would have been very simple, if not trivial, using a relational database with foreign keys, many-to-many relations, joins, etc. But the problem was that my application was targeted for Google App Engine and I had to design for a database that was not relational. At the end I gave up. Is there a book or an article that describes design principles for applications that are meant for such databases? The books that I have found are about programming for App Engine and they don't spend many words about database design principles.

  Read the article

• Relational databases are not suited for my application - what's the alternative?

  - by waitinforatrain

  Hi, I'm writing a CMS in PHP that allows the user to define different fields (e.g. a Blog page could have fields for Title (string), Content (rich text), Picture (file)). I need the user to be able to add and remove fields dynamically, and the only way I can think of to do it with relational DBs is to serialise all these values and store them in one cell. This seems like a slow approach and like I'm trying to fit something dynamic within a static structure. Could someone recommend anything that is PHP-compatible that would make this easier?

  Read the article

• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

  Read the article

• Is it possible to implement bitwise operators using integer arithmetic?

  - by Statement

  Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division (c = a / b) Multiplication (c = a * b) Modulus (c = a % b) Minimum (c = min(a, b)) Maximum (c = max(a, b)) Comparisons (c = (a < b), c = (a == b), c = (a <= b), et.c.) Jumps (goto, for, et.c.) The bitwise operations I want to be able to support are: Or (c = a | b) And (c = a & b) Xor (c = a ^ b) Left Shift (c = a << b) Right Shift (c = a b) (All integers are signed so this is a problem) Signed Shift (c = a b) One's Complement (a = ~b) (Already found a solution, see below) Normally the problem is the other way around; how to achieve arithmetic optimizations using bitwise hacks. However not in this case. Writable memory is very scarce on this architecture, hence the need for bitwise operations. The bitwise functions themselves should not use a lot of temporary variables. However, constant read-only data & instruction memory is abundant. A side note here also is that jumps and branches are not expensive and all data is readily cached. Jumps cost half the cycles as arithmetic (including load/store) instructions do. On other words, all of the above supported functions cost twice the cycles of a single jump. Some thoughts that might help: I figured out that you can do one's complement (negate bits) with the following code: // Bitwise one's complement b = ~a; // Arithmetic one's complement b = -1 - a; I also remember the old shift hack when dividing with a power of two so the bitwise shift can be expressed as: // Bitwise left shift b = a << 4; // Arithmetic left shift b = a * 16; // 2^4 = 16 // Signed right shift b = a >>> 4; // Arithmetic right shift b = a / 16; For the rest of the bitwise operations I am slightly clueless. I wish the architects of this architecture would have supplied bit-operations. I would also like to know if there is a fast/easy way of computing the power of two (for shift operations) without using a memory data table. A naive solution would be to jump into a field of multiplications: b = 1; switch (a) { case 15: b = b * 2; case 14: b = b * 2; // ... exploting fallthrough (instruction memory is magnitudes larger) case 2: b = b * 2; case 1: b = b * 2; } Or a Set & Jump approach: switch (a) { case 15: b = 32768; break; case 14: b = 16384; break; // ... exploiting the fact that a jump is faster than one additional mul // at the cost of doubling the instruction memory footprint. case 2: b = 4; break; case 1: b = 2; break; }

  Read the article

• Two '==' equality operators in same 'if' condition are not working as intended.

  - by Manav MN

  I am trying to establish equality of three equal variables, but the following code is not printing the obvious true answer which it should print. Can someone explain, how the compiler is parsing the given if condition internally? #include<stdio.h> int main() { int i = 123, j = 123, k = 123; if ( i == j == k) printf("Equal\n"); else printf("NOT Equal\n"); return 0; } Output: manav@workstation:~$ gcc -Wall -pedantic calc.c calc.c: In function ‘main’: calc.c:5: warning: suggest parentheses around comparison in operand of ‘==’ manav@workstation:~$ ./a.out NOT Equal manav@workstation:~$ EDIT: Going by the answers given below, is the following statement okay to check above equality? if ( (i==j) == (j==k))

  Read the article

• Is there a programming language with no controls structures or operators?

  - by Oscar Reyes

  Other than Smalltalk?

  Read the article

• Postfix and right-associative operators in LR(0) parsers

  - by Ian

  Is it possible to construct an LR(0) parser that could parse a language with both prefix and postfix operators? For example, if I had a grammar with the + (addition) and ! (factorial) operators with the usual precedence then 1+3! should be 1 + 3! = 1 + 6 = 7, but surely if the parser were LR(0) then when it had 1+3 on the stack it would reduce rather than shift? Also, do right associative operators pose a problem? For example, 2^3^4 should be 2^(3^4) but again, when the parser have 2^3 on the stack how would it know to reduce or shift? If this isn't possible is there still a way to use an LR(0) parser, possibly by converting the input into Polish or Reverse Polish notation or adding brackets in the appropriate places? Would this be done before, during or after the lexing stage?

  Read the article

• What is the difference between the * and the & operators in c programming?

  - by Wesley

  I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

  Read the article

• Why would one overload the && and & operator?

  - by acidzombie24

  The same question goes for | and ||. Why would one overload or 'use' the & and && operator? The only use i thought of are Bitwise Ands for int base types (but not float/decimals) using & logical short circuit for bools/functions that return bool. Using the && operator usually. I cant think of any classes that use those operators. Absolutely none. I know a class might support + (and not '-') which combine two strings together. I seen an object such as datetime overload '-' so two dates can be subtracted to make a timespan (obviously you cant add two dates) but i never seen &, &&, | and || used. Does anyone know of a use? In any language?

  Read the article

• Combining two operators in Evil-mode Emacs

  - by Dyslexic Tangent

  In vim I've remapped > and < when in visual mode to >gv and <gv respectively, like so: vnoremap > >gv vnoremap < <gv Since my target for this question are folks experienced with emacs and not vim, what > and < do is indent/dedent visually selected text. What gv does is reselect the previously selected text. These maps cause > and < to indent/dedent and then reselect the previously selected text. I'm trying out emacs with evil-mode and I'd like to do the same, but I'm having some difficulty figuring out how, exactly, to accomplish the automatic reselection. It looks like I need to somehow call evil-shift-right and evil-visual-restore sequentially, but I don't know how to create a map that will do both, so I tried creating my own function which would call both sequentially and map that instead, but it didn't work, possibly due to the fact that both of them are defined, not as functions with defun but instead as operators with evil-define-operator. I tried creating my own operators: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-restore)) but that doesn't restore visual as expected. A stab in the dark gave me this: (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) ('evil-visual-restore)) (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) ('evil-visual-restore)) but that selects one additional line whenever it is supposed to reselect. For now I've been using the following, which only has the problem where it reselects an additional line in the < operator. (evil-define-operator shift-right-reselect (beg end) (evil-shift-right beg end) (evil-visual-make-selection beg end)) (evil-define-operator shift-left-reselect (beg end) (evil-shift-left beg end) (evil-visual-make-selection beg end)) and I've mapped them: (define-key evil-visual-state-map ">" 'shift-right-reselect) (define-key evil-visual-state-map "<" 'shift-left-reselect) any help / pointers / tips would be greatly appreciated. Thanks in advance.

  Read the article

• Nagios3: Conditional operators for service checks?

  - by Dave

  I'm trying to setup Nagios to monitor my various using hostgroups to define 'machine roles', against which I run services to check the machines by role. However, I'd like to use conditional operators that would enable me to run the service check against an intersection of two host groups, rather than their unions... i.e. using &&, ||, or () operators. For example, imagine I have the following servers: www-eu: Linux WWW (Apache) server, in the EU www-us: Windows WWW (IIS) server, in the US (West coast) ftp-eu: Linux FTP server, in the EU ftp-us: Windows FTP server, in the US I would want to create the following host groups: US-Servers: www-us, ftp-us EU-Servers: www-eu, ftp-eu WWW-Servers: www-us, www-eu FTP-Servers: ftp-us, ftp-eu Now say I'm interested in checking the HTTP response time for my web servers. Then let's say this particular Nagios service is running from the US (West Coast), and that I have a command called *check_http_response_time*. This command will check the responsiveness of the HTTP server, which I can provide an argument which defines the max response time before raising critical. My command might look like: check_http_response_time $HOSTNAME$ 50 Now traditionally, I can run my checks by specifying a list of host or hostgroups. define service{ use local-service hostgroup_name WWW-Servers # Servers = www-us, www-eu servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } However, with the above service definition, given my Nagios service is in US West, I could reasonably expect that my EU server will return critical. Really, I want different thresholds for each region (50 for US West, 200 for EU.) I would have to permutate my service for each host and set their custom threshold, or alternatively permutate out my service groups by role & region (i.e. WWW-Servers-EU), and run my specific thresholds against those. Though the latter is better, both are much messier than I'd like... What I would love, and what this post is asking for, is a way to use hostgroups to perform an intersection using conditional logic, rather than a simple union. It might look like: define service{ use local-service hostgroup_name WWW-Servers && US-Servers servicegroups WWW Checks service_description Check HTTP Response Time check_command check_http_response_time!50 } It then would run the check only against servers that are in both WWW-Servers and US-Servers, in my example, just www-us. The benefits of such a feature would be significant for Nagios services configured for large-scale. Is this feature available? If it isn't, will it be available in the future? Is there an alternative way to accomplish this given the most recent Nagios version? Any tips/suggestions are most appreciated! Dave

  Read the article

• What is the most concise, unambiguous syntax for operator associated methods (for overloading etc.) that doesn't pollute the namespace?

  - by Doug Treadwell

  Python tends to add double underscores before its built-in or overloadable operator methods, like __add(), whereas C++ requires declaring overloaded operators as operator + (Thing& thing) { /* code */ } for example. Personally I like the operator syntax because it seems to be more explicit and keeps these operator overloading methods separated from other methods without introducing weird prefix notation. What are your thoughts? Also, what about the case of built-in methods that are needed for the programming language to work properly? Is name mangling (like adding __ prefix or sys or something) the best solution here? What do you think about having another type of method declaration, like ... "system method" for lack of creativity at the moment. So there would be two kinds of declarations: int method_name() { ... } system int method_name() { ... } ... and the call would need to be different to distinguish between them. obj.method_name(); vs obj:method_name(); perhaps, assuming a language where : can be unambiguously used in this situation. obj.method_name() vs obj.(system method_name)() Sure, the latter is ugly, but the idea is to make the common case simple and system stuff should be kept out of the way. Maybe the Objective-C notation of method calls? [obj method_name]? Are there more alternatives? Please make suggestions.

  Read the article

• Do ternary operators increase complexity in programs?

  - by Lucas McCoy

  Some people would rather user if statements then a ternary operator because they say the increase complexity in your programs. I personally like ternary operators, what is your opinion? Should you use if statements or ternary operators?

  Read the article

• Does SQL Azure Support Relational Databases?

  - by Goober

  I keep reading that SQL Azure doesn't support relational databases; however, I just tapped into my SQL Azure Database and scripted a relational database. I even checked to see what was present using: select * from sys.objects Any thoughts?

  Read the article

• XML flat file vs. relational database backend

  - by donpal

  Most projects now need some form of a database. When someone says database, I usually think relational databases, but I still hear about flat file XML databases. What parameters do you take into consideration when deciding between a "real" database and a flat-file XML database. When should one be used over the other, and under what circumstances should I never consider using a flat file (or vice versa a relational) database?

  Read the article

• Relational database question with php.

  - by Oliver Bayes-Shelton

  Hi, Not really a coding question more a little help with my idea of a Relational database. If I have 3 tables in a SQL database. In my php script I basically query the companies which are in industry "a" and then insert a row into a separate table with their details such as companyId , companyName etc is that a type of Relational database ? I have explained it in a simple way so we don't get confused what I am trying to say.

  Read the article

• Relational database queestion with php.

  - by Oliver Bayes-Shelton

  Hi, Not really a coding question more a little help with my idea of a Relational database. If I have 3 tables in a SQL database. In my php script I basically query the companies which are in industry "a" and then insert a row into a seperate table with their details such as companyId , companyName etc is that a type of Relational database ? I have explained it in a simple way so we don't get confused what I am trying to say.

  Read the article

• Twitter search API VS Operators

  - by supermogx

  I've found this page about the Twitter search API and some operators : http://search.twitter.com/operators But is it possible to make a search like : All posts containing the words "ipod OR ipad" AND all posts containing the words "funny OR joke" ? Like : "happy AND hour" OR "ipod AND ipad" this doesn't look like it's possible.

  Read the article

• Modeling Tools that understand both Relational and LDAP

  - by jm04469

  I am looking to do some modeling and would like to have a tool that can capture not only a relational model like ERWIN but also allow us to easily port to LDAP as an option. NOTE: Visio can connect to an existing LDAP server and draw, but does not allow for you to model first and then deploy, unlike its relational capabilities.

  Read the article

• Cuppa Corner talk "A trip to First Normal Form" available - Domains, Functional Dependencies, Repeat

  - by tonyrogerson

  It's 15 minutes, I talk about Domains, Functional Dependencies, Repeating Groups, Relational Valued Attributes and of course First Normal Form. http://sqlcontent.sqlblogcasts.com/video/cctr20100507dbdesign1nf/cctr20100507dbdesign1nf.html For questions just ask on the http://sqlserverfaq.com chat control or Twitter using #sqlfaq tag. Slides are also availble here: http://sqlcontent.sqlblogcasts.com/video/cctr20100507dbdesign1nf/cc_tr20100507_dbdesign1nf.pptx...(read more)

  Read the article

• Technology Selection for a dynamic product

  - by Kuntal Shah

  We are building a product for Procurement Domain in JAVA. Following are the main technical requirements. Platform Independent Database Independent Browser Independent In functional requirements the product is very dynamic in nature. The main reason being the procurement process around the world is different from client to client. Briefly we need to have a dynamic workflow engine and a dynamic template engine. The workflow engine by which we can define any kind of workflows and the template engine allows us to define any kind of data structures and based on definition it can get the user input through workflow. We have been developing this product for almost 2 years. It has been a long time till we can get down with the dynamics of requirements. Till now we have developed a basic workflow and template engine and which is in use at one of the client. We have been using following technologies. GWT-Ext (Front End Framework) Hibernate (Database Layer) In between we have faced some issues with GWT-Ext (mainly browser compatibility) and database optimization due to sub classing in hibernate. For resolving GWT-Ext issue, which a dying community so we decided to move to SmartGWT. In SmartGWT we faced issues related to loading and now we are able to finalize that GWT 2.3 will be the way to go as the library is rich and performance is upto the mark. We are able to almost finalize GWT-Spring based front and middle layer. In hibernate, we found main issues with sub-classing due to that it was throwing astronomical queries and sometimes it would stop firing any queries for 5-10 seconds or may be around 30 seconds and then resume again. Few days back I came to one article related to ORM. I am a traditional .Net SQL developer and I have always worked with relational database. Reading through this article, I also found it relating to the issues I face. I am still not completely convinced of using hibernate and this article just supported my opinion. Following are the questions for which I am looking for an answer. Should we be going with Hibernate in case of dynamic database requirements and the load of the data will be heavy in future? How can we partition the data, how we can efficiently join the data, how we can optimize the queries? If the answer is no then how do we achieve database independence? Is our choice related to GWT and Spring proper or do we need to change that too? Should we use any other key value pair database if the data is dynamic in nature and it is very difficult to make it relational?

  Read the article

• Should database-models (conceptual or physical) be reviewed by DBAs?

  - by user61852

  Where I work, new applications that are being developed that will use their own relational database, must have their database-models (conceptual, then physical ) reviewed and aproved by DBAs. Things looked after are normalization, antipatterns, table and column naming standards, etc. Is this really a DBA's responsability to do this ? or should it be, in a greater extend, the responsability of app designers and architects ?

  Read the article

• Custom Java Web Development vs Spreadsheet

  - by jacktrades

  Need some arguments why a small business should prefer a custom web developed solution using relational database (e.g. Java Servlet + MySQL) over standard Spreadsheet user programs like Excel. Specially now in these days that Office 365 is available in the cloud. As a Java programmer need good arguments to convince clients that this approach is better (if it really is) This is a generic situation, I understand that each case is different. Nevertheless answers so far has pinpointed right answers.

  Read the article

• I have a KVP Key value pair Table, Need sql to make it relational structure...!

  - by Muthuveerappan

  I have a KVP Table and the structure is ID, Key, Value and below are the sample values.... Table with values ID , Key, Value 1 , STATUS, TRUE 1, AGE GROUP, 10 1, TRAVEL, Y 2 , STATUS, FALSE 2, AGE GROUP, 20 2, TRAVEL, N I want these date to transform as below (Output) ID , STATUS, AGE GROUP, TRAVEL 1, TRUE , 10, Y 2, FALSE, 20, N I have read about crosstab/pivot - but not able to make a query which can give me the above output. The table structure cant be changed...! My bad. Is there any way in sql, to make my output look like above ?

  Read the article

• How do I insert data into a object relational table with multiple ref in the schema.

  - by Yiling

  I have a table with a schema of Table(number, ref, ref, varchar2, varchar2,...). How would I insert a row of data into this table? When I do: "insert into table values (1, select ref(p), ref(d), '239 F.3d 1343', '35 USC § 283', ... from plaintiff p, defendant d where p.name='name1' and d.name='name2');" I get a "missing expression" error. If I do: "insert into table 1, select ref(p), ref(d), ... from plaintiff p, defendant where p.name=...;" I get a "missing keyword VALUES" error.

  Read the article

< Previous Page | 3 4 5 6 7 8 9 10 11 12 13 14  | Next Page >