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  • Database indexes and their Big-O notation

    - by miket2e
    I'm trying to understand the performance of database indexes in terms of Big-O notation. Without knowing much about it, I would guess that: Querying on a primary key or unique index will give you a O(1) lookup time. Querying on a non-unique index will also give a O(1) time, albeit maybe the '1' is slower than for the unique index (?) Querying on a column without an index will give a O(N) lookup time (full table scan). Is this generally correct ? Will querying on a primary key ever give worse performance than O(1) ? My specific concern is for SQLite, but I'd be interested in knowing to what extent this varies between different databases too.

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  • SQL trigger to delete rows from database

    - by wpearse
    I have an industrial system that logs alarms to a remotely hosted MySQL database. The industrial system inserts a new row whenever a property of the alarm changes (such as the time the alarm was activated, acknowledged or switched off) into a table named 'alarms'. I don't want multiple records for each alarm, so I have set up two database triggers. The first trigger mirrors each new record to a second table, creating/updating rows as required: CREATE TRIGGER `mirror_alarms` BEFORE INSERT ON `alarms` FOR EACH ROW INSERT INTO `alarm_display` (Tag,...,OffTime) VALUES (new.Tag,...,new.OffTime) ON DUPLICATE KEY UPDATE OnDate=new.OnDate,...,OffTime=new.OffTime The second trigger should execute after the first and (ideally) delete all rows from the alarms table. (I used the Tag property of the alarm because the Tag property never changes, although I suspect I could just use a 'DELETE FROM alarms WHERE 1' statement to the same effect). CREATE TRIGGER `remove_alarms` AFTER INSERT ON `alarms` FOR EACH ROW DELETE FROM alarms WHERE Tag=new.Tag My problem is that the second trigger doesn't appear to run, or if it does, the second trigger doesn't delete any rows from the database. So here's the question: why does my second trigger not do what I expect it to do?

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  • what type of errors can we handle using system define unnamed exception in sqlplus?

    - by Aspirant
    I have been trying to access the below code DECLARE N_DEPTNO DEPT.DEPTNO %TYPE :=&DEPT_NUM; V_DNAME DEPT.DNAME %TYPE; NOT_ENOUGH_VALUES EXCEPTION; PRAGMA EXCEPTION_INIT(NOT_ENOUGH_VALUES,-06502); BEGIN SELECT DNAME,LOC INTO DNAME FROM DEPT WHERE DEPTNO = N_DEPTNO; DBMS_OUTPUT.PUT_LINE('Successfully Fetched !!'); EXCEPTION WHEN NOT_ENOUGH_VALUES THEN DBMS_OUTPUT.PUT_LINE('No Enough Values ... '); END; It is still showing error message after specified it in EXCEPTION block. Can i handle these type of errors using PRAGMA EXCEPTION_INIT i.e not providing enough values in the select statement... If not what type of errors can be handled in System Defined Unnamed Exception using PRAGMA EXCEPTION_INIT.

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  • How to select parent row only if has at least one child?

    - by Matt McCormick
    I have a simple one-to-many relationship. I would like to select rows from the parent only when they have at least one child. So, if there are no children, then the parent row is not returned in the result set. Eg. Parent: +--+---------+ |id| text | +--+---------+ | 1| Blah | | 2| Blah2 | | 3| Blah3 | +--+---------+ Children +--+------+-------+ |id|parent| other | +--+------+-------+ | 1| 1 | blah | | 2| 1 | blah2 | | 3| 2 | blah3 | +--+------+-------+ I want the results to be: +----+------+ |p.id|p.text| +----+------+ | 1 | Blah | | 2 | Blah2| +----+------+

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  • How can I set my deployment options to script the incremental release of a Visual Studio 2010 databa

    - by littlechris
    I've just started using a VS2010 database project to manage the release of an update to an existing database. I want the deployment option to generate a script that will contain the commands to change my existing database rather than create an entirely new one. E.g I have 10 existing tables - one of which I drop in the new version and I create some new sprocs. I only want the deploy to script the Drop table and Create Procedure commands. I am using VS2010 Premium. Thanks!

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  • select all values from a dimension for which there are facts in all other dimensions

    - by ideasculptor
    I've tried to simplify for the purposes of asking this question. Hopefully, this will be comprehensible. Basically, I have a fact table with a time dimension, another dimension, and a hierarchical dimension. For the purposes of the question, let's assume the hierarchical dimension is zip code and state. The other dimension is just descriptive. Let's call it 'customer' Let's assume there are 50 customers. I need to find the set of states for which there is at least one zip code in which EVERY customer has at least one fact row for each day in the time dimension. If a zip code has only 49 customers, I don't care about it. If even one of the 50 customers doesn't have a value for even 1 day in a zip code, I don't care about it. Finally, I also need to know which zip codes qualified the state for selection. Note, there is no requirement that every zip code have a full data set - only that at least one zip code does. I don't mind making multiple queries and doing some processing on the client side. This is a dataset that only needs to be generated once per day and can be cached. I don't even see a particularly clean way to do it with multiple queries short of simply brute-force iteration, and there are a heck of a lot of 'zip codes' in the data set (not actually zip codes, but the there are approximately 100,000 entries in the lower level of the hierarchy and several hundred in the top level, so zipcode-state is a reasonable analogy)

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  • count(*) is it really expensive ?

    - by Anil Namde
    I have a page where i have 4 tabs displaying 4 different reports based of different tables. Now i get row count of each tabled using select count() from table query and display number of rows available in each table on the tabs. Now with each page post back 5 count() queries are executed (4 to get counts and 1 for pagination) and 1 query for getting report. Now my question is should is count(*) query really expensive that i should keep the row counts (at least which are displayed on tab) in view state of page instead of queering each time? How much expensive it is ?

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  • How Can I Reference Multiple Primary Keys For A Vector Type Primary Key

    - by AndreiC
    Hi, I have the following scenario: a table of projects and a table of persons, working on one or serveral projects. Also, I have a project id column (of type int), in the first table, which is a primary key there and I have a vector of project ids, as a column of type int, in my second table (persons), that references primary keys from the first table. What is the correct syntax for referencing multiple primary keys, from a vector foreign key. This is the way I am trying to create the table, but I am not sure what to place at the indicated line: CREATE TABLE Persons( Person_Id int, ..., ProjectsList int[], FOREIGN KEY (ProjectsList) REFERENCES Projects(Project_id) -- not sure what how to define the link here ); I hope my explanations are not over-complicated. Thank you in advance for helping!

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  • I want to run two or more procedures in parallel

    - by binod gyawali
    I have list of procedures. All procedures are not dependent upon each other. So, I need to do is, to run the independent procedures in parallel. I have 4 procedures that are to be run parallel. When the procedures are run successfully, now I need to go to the next task. These procedures create about 10 tables. Next task is to execute the set of procedures. I have made one table, where I describe the dependency of these procedures to the tables created above. After any one of the above procedures is completed, I should come to this set of procedures, and find out those procedures whose dependency tables are already created. If any procedure whose dependent tables creation is completed, I need to execute this procedure. Running 4 procedures parallel is done by dts. But, difficulty for me is to transfer the task from the above 4 procedures to the below set of procedures. Please help me to complete my task. Thanks in advance

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  • HTML5 Web Database Security

    - by Daniel Dimovski
    Should the HTML5 database be used to store any form of private information? Say we have the following scenario; You're browsing a web-mail client, that uses the web database to store mail drafts after you've written some information you close the web browser. What's to stop me from getting access to this information? If the webpage tries to clean out old information when opened a user-script could easily prevent the website from fully loading and then search through the database. Furthermore the names of databases and tables are easily available through the web-mail client's source. W3C Draft

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  • What is wrong with this connection string?

    - by Hakan
    Can any one help me with this connection string. I can't manage how to fix. Dim constring As String Dim con As SqlCeConnection Dim cmd As SqlCeCommand constring = "(System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase) + \\database.sdf;Password=pswrd;File Mode=shared read" con = New SqlCeConnection() con.Open() Thanks

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  • How can I format Custom Data and display in autocomplete when source is an DB

    - by Andres Scarpone
    so I'm trying to get some info in the auto-complete widget like it's shown in the JQuery UI demo Demo, the only problem is they use a variable that they fill with the data they want to show, I instead want to access the data and the different description and stuff using a Data Base in MySQL, for this I have changed the source to use another php page that looks up the info. here is the code for the Auto-complete, I really don't understand the methods so I haven't changed it from the basic search. This is the JS: $(document).ready((function(){ $( "#completa" ).autocomplete({ source: "buscar.php", minLength: 1, focus: function (event, ui){ $("#completa").val(ui.item.val); return false; }; })); This is what I have in buscar.php: <?php $conec = mysql_connect(localhost, root, admin); if(!$conec) { die(mysql_error()); } else { $bd = mysql_select_db("ve_test",$conec ); if(!$bd) { die(mysql_error()); } } $termino = trim(strip_tags($_GET['term']));//Obtener el termino que envia el autocompletar $qstring = "SELECT name, descripcion FROM VE_table WHERE name LIKE '%".$termino."%'"; $result = mysql_query($qstring);//Solicitud a la Base de Datos while ($row = mysql_fetch_array($result,MYSQL_ASSOC))//Realizar un LOOP sobre los valores obtenidos { $row['value']=htmlentities(stripslashes($row['name'])); $row_set[] = $row;//build an array } echo json_encode($row_set);//Enviar los datos al autocompletar en codificacion JSON, Altamente Necesario. ?

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  • validate linqtosql mapping to a model

    - by Coppermill
    I have generated a LinqtoSQL mapping xml file, which I have a valid XSD schema that I check to make sure the XML is correct. Now I want to check that the field type match the Model/Interface for example: checking that the nullable fields are nullable that int are int etc anyone got any ideas if I can do this?

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  • How to combine a list of choices to determine which select statement

    - by Larry
    I have a mysql db and am using php 5.2 What I am trying to do is offer a list of options for a person to select (only 1). The chosen option will cause a select, update, or delete statement to be ran. The results of the statement do not need to be shown, although, showing the old and then the new would be nice (no problems with that part tho'.). Pseudo-Code: Assign $choice = 0 Check the value of $choice // This way, if it = 100, we do a break Select a Choice:<br> 1. Adjust Status Value (+60) // $choice = 1<br> 2. Show all Ships <br> // $choice = 2 3. Show Ships in Port <br> // $choice = 3 ... 0. $choice="100" // if the value =100, quit this part Use either case (switch) or if/else statements to run the users choice1 If the choice is 1, then run the "Select" statement with the variable of $sql1 -- "SELECT .... If the choice is 2, then run the "Select" statement with the variable of $sql2 --- SELECT * FROM Ships If the choice is 3, then run the "Select" statement with the variable of $sql3 <br> .... If the choice is 0, then we are done. I figured the (3) statements would be assigned in php as: $sql1="...". $sql2="SELECT * FROM Ships" $sql3="SELECT * FROM Ships WHERE nPort="1" My idea was to use the switch statement, but got lost on it. :( I would like the options to be available over and over again, until a variable ($choice) is selected. In which case, this particular page is done and goes back to the "Main Menu"? The coding and display, if I use it, I can do. Just not sure how to write the way to select which one I want. It is possible that I would run all of the queries, and other times, only one, so that is why I would like the choice. An area I get confused in is the proper forms to use such as -- ' ' " " and ...?? Not sure the # of options I will end up with, but it will be more than 5 but less than 20 / page. So if I get the system down for 2-3 choices, I can replicate it for as many as I may need. And, as always, if a better way exists, I am willing to try it. Thanks again... Larry

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  • Compare values in serialized column in Doctrine with Query Builder

    - by ReynierPM
    I'm building a FormType for a Symfony2 project but I need some Query Builder on the field since I need to compare some values with the one stored on DB and show the results. This is what I have: .... ->add('servicio', 'entity', array( 'mapped' => false, 'class' => 'ComunBundle:TipoServicio', 'property' => 'nombre', 'required' => true, 'label' => false, 'expanded' => true, 'multiple' => true, 'query_builder' => function (EntityRepository $er) { return $er->createQueryBuilder('ts') ->where('ts.tipo_usuario = (:tipo)') ->setParameter('tipo', 1); } )) .... But tipo_usuario at DB table is stored as serialized text for example: record1: value1 | a:1:{i:0;s:1:"1";} record2: value2 | a:4:{i:0;s:1:"1";i:1;s:1:"2";i:2;s:1:"3";i:3;s:1:"4";} I'll have two different forms (I don't know how to pass the Request to a form) in the first one I'll only show the first record and for the second one the first and second record for example: First form will show: checkbox: value1 Second form will show: checkbox: value1 checkbox: value2 I achieve this? Any help?

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  • how to avoid sub-query to gain performance

    - by chun
    hi i have a reporting query which have 2 long sub-query SELECT r1.code_centre, r1.libelle_centre, r1.id_equipe, r1.equipe, r1.id_file_attente, r1.libelle_file_attente,r1.id_date, r1.tranche, r1.id_granularite_de_periode,r1.granularite, r1.ContactsTraites, r1.ContactsenParcage, r1.ContactsenComm, r1.DureeTraitementContacts, r1.DureeComm, r1.DureeParcage, r2.AgentsConnectes, r2.DureeConnexion, r2.DureeTraitementAgents, r2.DureePostTraitement FROM ( SELECT cc.id_centre_contact, cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe, a.id_file_attente, f.libelle_file_attente, a.id_date, g.tranche, g.id_granularite_de_periode, g.granularite, sum(Nb_Contacts_Traites) as ContactsTraites, sum(Nb_Contacts_en_Parcage) as ContactsenParcage, sum(Nb_Contacts_en_Communication) as ContactsenComm, sum(Duree_Traitement/1000) as DureeTraitementContacts, sum(Duree_Communication / 1000 + Duree_Conference / 1000 + Duree_Com_Interagent / 1000) as DureeComm, sum(Duree_Parcage/1000) as DureeParcage FROM agr_synthese_activite_media_fa_agent a, centre_contact cc, direction_contact dc, granularite_de_periode g, media m, file_attente f WHERE m.id_media = a.id_media AND cc.id_centre_contact = a.id_centre_contact AND a.id_direction_contact = dc.id_direction_contact AND dc.direction_contact ='INCOMING' AND a.id_file_attente = f.id_file_attente AND m.media = 'PHONE' AND ( ( g.valeur_min = date_format(a.id_date,'%d/%m') and g.granularite = 'Jour') or ( g.granularite = 'Heure' and a.id_th_heure = g.id_granularite_de_periode) ) GROUP by cc.id_centre_contact, a.id_equipe, a.id_file_attente, a.id_date, g.tranche, g.id_granularite_de_periode) r1, ( (SELECT cc.id_centre_contact,cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe, a.id_date, g.tranche, g.id_granularite_de_periode,g.granularite, count(distinct a.id_agent) as AgentsConnectes, sum(Duree_Connexion / 1000) as DureeConnexion, sum(Duree_en_Traitement / 1000) as DureeTraitementAgents, sum(Duree_en_PostTraitement / 1000) as DureePostTraitement FROM activite_agent a, centre_contact cc, granularite_de_periode g WHERE ( g.valeur_min = date_format(a.id_date,'%d/%m') and g.granularite = 'Jour') AND cc.id_centre_contact = a.id_centre_contact GROUP BY cc.id_centre_contact, a.id_equipe, a.id_date, g.tranche, g.id_granularite_de_periode ) UNION (SELECT cc.id_centre_contact,cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe, a.id_date, g.tranche, g.id_granularite_de_periode,g.granularite, count(distinct a.id_agent) as AgentsConnectes, sum(Duree_Connexion / 1000) as DureeConnexion, sum(Duree_en_Traitement / 1000) as DureeTraitementAgents, sum(Duree_en_PostTraitement / 1000) as DureePostTraitement FROM activite_agent a, centre_contact cc, granularite_de_periode g WHERE ( g.granularite = 'Heure' AND a.id_th_heure = g.id_granularite_de_periode) AND cc.id_centre_contact = a.id_centre_contact GROUP BY cc.id_centre_contact,a.id_equipe, a.id_date, g.tranche, g.id_granularite_de_periode) ) r2 WHERE r1.id_centre_contact = r2.id_centre_contact AND r1.id_equipe = r2.id_equipe AND r1.id_date = r2.id_date AND r1.tranche = r2.tranche AND r1.id_granularite_de_periode = r2.id_granularite_de_periode GROUP BY r1.id_centre_contact , r1.id_equipe, r1.id_file_attente, r1.id_date, r1.tranche, r1.id_granularite_de_periode ORDER BY r1.code_centre, r1.libelle_centre, r1.equipe, r1.libelle_file_attente, r1.id_date, r1.id_granularite_de_periode,r1.tranche the EXPLAIN shows | id | select_type | table | type| possible_keys | key | key_len | ref| rows | Extra | '1', 'PRIMARY', '<derived3>', 'ALL', NULL, NULL, NULL, NULL, '2520', 'Using temporary; Using filesort' '1', 'PRIMARY', '<derived2>', 'ALL', NULL, NULL, NULL, NULL, '4378', 'Using where; Using join buffer' '3', 'DERIVED', 'a', 'ALL', 'fk_Activite_Agent_centre_contact', NULL, NULL, NULL, '83433', 'Using temporary; Using filesort' '3', 'DERIVED', 'g', 'ref', 'Index_granularite,Index_Valeur_min', 'Index_Valeur_min', '23', 'func', '1', 'Using where' '3', 'DERIVED', 'cc', 'ALL', 'PRIMARY', NULL, NULL, NULL, '6', 'Using where; Using join buffer' '4', 'UNION', 'g', 'ref', 'PRIMARY,Index_granularite', 'Index_granularite', '23', '', '24', 'Using where; Using temporary; Using filesort' '4', 'UNION', 'a', 'ref', 'fk_Activite_Agent_centre_contact,fk_activite_agent_TH_heure', 'fk_activite_agent_TH_heure', '5', 'reporting_acd.g.Id_Granularite_de_periode', '2979', 'Using where' '4', 'UNION', 'cc', 'ALL', 'PRIMARY', NULL, NULL, NULL, '6', 'Using where; Using join buffer' NULL, 'UNION RESULT', '<union3,4>', 'ALL', NULL, NULL, NULL, NULL, NULL, '' '2', 'DERIVED', 'g', 'range', 'PRIMARY,Index_granularite,Index_Valeur_min', 'Index_granularite', '23', NULL, '389', 'Using where; Using temporary; Using filesort' '2', 'DERIVED', 'a', 'ALL', 'fk_agr_synthese_activite_media_fa_agent_centre_contact,fk_agr_synthese_activite_media_fa_agent_direction_contact,fk_agr_synthese_activite_media_fa_agent_file_attente,fk_agr_synthese_activite_media_fa_agent_media,fk_agr_synthese_activite_media_fa_agent_th_heure', NULL, NULL, NULL, '20903', 'Using where; Using join buffer' '2', 'DERIVED', 'cc', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Centre_Contact', '1', '' '2', 'DERIVED', 'f', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_File_Attente', '1', '' '2', 'DERIVED', 'dc', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Direction_Contact', '1', 'Using where' '2', 'DERIVED', 'm', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Media', '1', 'Using where' don't know it very clear, but i think is the problem of seems it take full scaning than i change all the sub-query to views(create view as select sub-query), and the result is the same thanks for any advice

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  • Linq Distinct() by name for populate a dropdown list with name and value

    - by AndreMiranda
    I'm trying to populate a Drop down list with pharmaceutical companies, like Bayer, Medley etc. And, I'm getting theses names from DB and theses names are repeated in DB, but with different id's. I'm trying to use Linq Distinct(), but I don't want to use the equality comparer. Is there another way? My drop down list must be filled with the id and the name of the company. I'm trying something like: var x = _partnerService .SelectPartners() .Select(c => new {codPartner = c.codPartner, name = c.name}) .Distinct(); This is showing repeated companies in ddl. thanks!

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  • Storing users in a database

    - by EMcKenna
    Im wondering whats the best way of storing different types of users in my database. I am writing an application that has 4 main user types (admin, school, teacher, student). At the moment I have a table for each of these but i'm not sure thats the best way of storing user information. For instance... Allowing students to PM other student is simple (store sender and receiver student_id) but enabling teachers to PM students requires another table (sender teacher_id, sender student_id). Should all users be stored in one users table with a user_type field? If so, the teacher / student specific information will still have to be stored in another table. users user_id, password_hash, user_type students user_id, student_specific_stuff... teachers user_id, teacher_specific_stuff... How do I stop a user who has a user_type = student from being accidentally being entered into the teachers table (as both have a user_id) Just want to make sure I get the database correct before i go any further. Thanks...

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  • Select statement with multiple 'where' fields using same value without duplicating text

    - by kdbdallas
    I will start by saying that I don't think what I want can be done, but that said, I am hoping I am wrong and someone knows more than me. So here is your chance... Prove you are smarter than me :) I want to do a search against a SQLite table looking for any records that "are similar" without having to write out the query in long hand. To clarify this is how I know I can write the query: select * from Articles where title like '%Bla%' or category like '%Bla%' or post like '%Bla%' This works and is not a huge deal if you are only checking against a couple of columns, but if you need to check against a bunch then your query can get really long and nasty looking really fast, not to mention the chance for typos. (ie: 'Bla%' instead of '%Bla%') What I am wondering is if there is a short hand way to do this? *This next code does not work the way I want, but just shows kind of what I am looking for select * from Articles where title or category or post like '%Bla%' Anyone know if there is a way to specify that multiple 'where' columns should use the same search value without listing that same search value for every column? Thanks in advance!

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  • SQLServer using too much memory

    - by Israel Pereira Valverde
    I have installed on my desktop machine (with windows 7) SQLServer 2008 R2 Express. I have only one local server running (./SQLEXPRESS) but the sqlserver process is taking ALL the RAM possible. With an machine with 3GB of RAM the things starts to get slow, so I limited the maximun amount of RAM in the server, and now, constantly the SQLServer give some error messages that the memory is not enought. It's using 1GB of RAM with only one LOCAL server with 2 databases completely empty, how 1GB of RAM isn't enought ? When the process start it's using an really acceptable amount of memory (around 80MB) but it's keep increasing until it reaches the maximun defined and start to complain about having not enought memory available. In that point I have to restart the server to use it again. I have read about an hotfix to solve one of the errors I got from sqlserver: There is insufficient system memory in resource pool 'internal' to run this query But it's already installed on my sqlserver. Why it's using so much memory?

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  • What is the difference between these two LINQ statements?

    - by jamone
    I had the 1nd statement in my code and found it not giving an accurate count, it was returning 1 when the correct answer is 18. To try and debug the problem I broke it out creating the 2nd statement here and the count returns 18. I just don't see what the difference is between these two. It seems like the 1st is just more compact. I'm currently running these two statements back to back and I'm sure that the database isn't changing between the two. int count = (from s in surveysThisQuarter where s.FacilityID == facility.LocationID select s.Deficiencies).Count(); vs var tempSurveys = from s in surveysThisQuarter where s.FacilityID == facility.LocationID select s; int count = 0; foreach (Survey s in tempSurveys) count += s.Deficiencies.Count();

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  • mysqli_stmt_bind_param SQL Injection

    - by profitphp
    Is there still an injection risk when using prepared statements and mysqli_stmt_bind_param? For example: $malicious_input = 'bob"; drop table users'; mysqli_stmt_bind_param($stmt, 's', $malicious_input); Behind the scenes does mysqli_stmt_bind_param pass this query string to mysql: SET @username = "bob"; drop table users"; Or does it perform the SET command through the API, or use some type of protection to keep this from happening?

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