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  • Questions regarding databases MS Access [on hold]

    - by user2977751
    Good day! I am using MS Access 2007. I was wondering, how can I link a specific item on a table to another item in another table? For example, if I search for a particular product, all the suppliers of that product will be displayed. I want to connect my supply field to different suppliers field in different tables so that when I search for a particular supply, all the suppliers for that supply will be shown. And if it is also possible to link the records into a pre-set template in excel. THANKS!

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  • .NET DB Query Without Allocations?

    - by Michael Covelli
    I have been given the task of re-writing some libraries written in C# so that there are no allocations once startup is completed. I just got to one project that does some DB queries over an OdbcConnection every 30 seconds. I've always just used .ExecuteReader() which creates an OdbcDataReader. Is there any pattern (like the SocketAsyncEventArgs socket pattern) that lets you re-use your own OdbcDataReader? Or some other clever way to avoid allocations? I haven't bothered to learn LINQ since all the dbs at work are Oracle based and the last I checked, there was no official Linq To Oracle provider. But if there's a way to do this in Linq, I could use one of the third-party ones.

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  • "=null" and select statement!

    - by user329820
    Hi I have asked this question before in this forum and they told me that it will retun an empty result set,I want to know that if I set the column with null values it will retun an empty result set?also the ANSI_NULLS is OFF ,thanks SELECT 'A' FROM T WHERE A = NULL;

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  • Clustered Index

    - by Charu
    Which type of index(clustered/non clustrered) should be used for Insert/Update/Delete statement in SQL Server. I know it creates an additional overhead but is it better in performance as comparison to non clustered index? Also which index should be use for Select statements in SQL Server?

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  • Which of these queries is more efficient?

    - by Brian
    Which of these queries are more efficient? select 1 as newAndClosed from sysibm.sysdummy1 where exists ( select 1 from items where new = 1 ) and not exists ( select 1 from status where open = 1 ) select 1 as newAndClosed from items where new = 1 and not exists ( select 1 from status where open = 1 )

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  • What statistics app should I use for my website?

    - by Camran
    I have my own server (with root access). I need statistics of users who visit my website etc etc... I have looked at an app called Webalyzer... Is this a good choice? I run apache2 on a Ubuntu 9 system... If you know of any good statistics apps for servers please let me know. And a follow-up question: All statistics are saved in log-files right? So how large would these log-files become then? Possibility to split them would be good, dont know if this is possible with Webalyzer though...

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  • php mysql_fetch_array() error

    - by user1877823
    I am getting this error while i am trying to delete a record the query is working but this line remains on the page. i want to echo "Deleted" written in the while should show up but the while loop is not working, i have tried and searched alot nothing helps! mysql_fetch_array() expects parameter 1 to be resource, boolean given in delete.php on line 27 delete.php <html> <body> <form method="post"> Id : <input type="text" name="id"> Name : <input type="text" name="name"> Description : <input type="text" name="des"> <input type="submit" value="delete" name="delete"> </form> <?php include("connect.php"); $id = $_POST['id']; $name = $_POST['name']; $des = $_POST['des']; $result = mysql_query("DELETE FROM fact WHERE id='$id'") or die(mysql_error()); while($row = mysql_fetch_array($result)) { echo "Deleted"; } mysql_close($con); ?> </body> </html> connect.php <?php $con = mysql_connect("localhost","root",""); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("Dataentry", $con); ?> How should i make the while loop work..

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  • Check mysql_query results if DELETE query worked?

    - by Camran
    I have a DELETE query which deletes a record from a mysql db. is there any way to make sure if the delete was performed or not? I mean, for a query to FIND stuff you do $res=mysql_query($var); $nr=mysql_num_rows($res); and you get nr of rows returned. Is there any similiar method for deletion of records? Thanks

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  • Solr authentication possible? (or apache port authentication would also work)

    - by Camran
    Currently anybody can access the solr admin page by going to my_ip:8983/solr I can't have it like that, so how can I make it prompt for password or something? I have setup my servers apache2.conf file to prompt for password whenever my site is accessed by www.mydomain.com. But when using another port, the "require password" wont show up. Any ideas how to secure this? Don't point me to the SolrSecurity wiki because it's simply too outdated. I have tried it without luck. Thanks

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  • How should I structure my settings table with mysql?

    - by incrediman
    I want to use MySQL to store a bunch of admin settings - what's the best way to structure the table? Like this? Setting _|_ Value setting1 | a setting2 | b setting3 | c setting4 | d setting5 | e Or like this? |--------|_setting1_|_setting2_|_setting3_|_setting4_|_setting5_| Settings | a | b | c | d | e | Or maybe some other way?

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  • many-to-many relationship in CI (not using ORM)

    - by Ross
    I'm implementing a categories system in my CI app and trying to work out the best way of working with many to many relationships. I'm not using an ORM at this stage, but could use say Doctrine if necessary. Each entry may have multiple categories. I have three tables (simplified) Entries: entryID, entryName Categories: categoryID, categoryname Entry_Category: entryID, categoryID my CI code returns a record set like this: entryID, entryName, categoryID, categoryName but, as expected with Many-to-Many relationships, each "entry" is repeated for each "category". What would the best way to "group" the categories so that when I output the results, I am left with something like: Entry Name Appears in Category: Foo, Bar rather than: Entry Name Appears in Category: Foo Entry Name Appears in Category: Bar I believe the option is to track if the post ID matches a previous entry, and if so, store the respective category, and output it as one, rather than several, but am unsure of how to do this in CI. thanks for any pointers (I appreciate this is may be a vague/complex question without a better knowledge of the system).

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  • How to restore a slave from a mysql backup?

    - by robsf
    I'm running MySql 5.1. I have Master and a Slave on 2 machines and I set up replication. I do periodic backup on my slave server. I stop mysql, I copy all the files and I restart mysql. In case I lose the Master, I can set up a new one from the last backup. What If I lose the Slave? Can I restart the slave from the last backup? Am I supposed to keep track of the position of the replication every time I to a backup?

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  • Understanding LINQ to SQL (11) Performance

    - by Dixin
    [LINQ via C# series] LINQ to SQL has a lot of great features like strong typing query compilation deferred execution declarative paradigm etc., which are very productive. Of course, these cannot be free, and one price is the performance. O/R mapping overhead Because LINQ to SQL is based on O/R mapping, one obvious overhead is, data changing usually requires data retrieving:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { Product product = database.Products.Single(item => item.ProductID == id); // SELECT... product.UnitPrice = unitPrice; // UPDATE... database.SubmitChanges(); } } Before updating an entity, that entity has to be retrieved by an extra SELECT query. This is slower than direct data update via ADO.NET:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (SqlConnection connection = new SqlConnection( "Data Source=localhost;Initial Catalog=Northwind;Integrated Security=True")) using (SqlCommand command = new SqlCommand( @"UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID", connection)) { command.Parameters.Add("@ProductID", SqlDbType.Int).Value = id; command.Parameters.Add("@UnitPrice", SqlDbType.Money).Value = unitPrice; connection.Open(); command.Transaction = connection.BeginTransaction(); command.ExecuteNonQuery(); // UPDATE... command.Transaction.Commit(); } } The above imperative code specifies the “how to do” details with better performance. For the same reason, some articles from Internet insist that, when updating data via LINQ to SQL, the above declarative code should be replaced by:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.ExecuteCommand( "UPDATE [dbo].[Products] SET [UnitPrice] = {0} WHERE [ProductID] = {1}", id, unitPrice); } } Or just create a stored procedure:CREATE PROCEDURE [dbo].[UpdateProductUnitPrice] ( @ProductID INT, @UnitPrice MONEY ) AS BEGIN BEGIN TRANSACTION UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID COMMIT TRANSACTION END and map it as a method of NorthwindDataContext (explained in this post):private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.UpdateProductUnitPrice(id, unitPrice); } } As a normal trade off for O/R mapping, a decision has to be made between performance overhead and programming productivity according to the case. In a developer’s perspective, if O/R mapping is chosen, I consistently choose the declarative LINQ code, unless this kind of overhead is unacceptable. Data retrieving overhead After talking about the O/R mapping specific issue. Now look into the LINQ to SQL specific issues, for example, performance in the data retrieving process. The previous post has explained that the SQL translating and executing is complex. Actually, the LINQ to SQL pipeline is similar to the compiler pipeline. It consists of about 15 steps to translate an C# expression tree to SQL statement, which can be categorized as: Convert: Invoke SqlProvider.BuildQuery() to convert the tree of Expression nodes into a tree of SqlNode nodes; Bind: Used visitor pattern to figure out the meanings of names according to the mapping info, like a property for a column, etc.; Flatten: Figure out the hierarchy of the query; Rewrite: for SQL Server 2000, if needed Reduce: Remove the unnecessary information from the tree. Parameterize Format: Generate the SQL statement string; Parameterize: Figure out the parameters, for example, a reference to a local variable should be a parameter in SQL; Materialize: Executes the reader and convert the result back into typed objects. So for each data retrieving, even for data retrieving which looks simple: private static Product[] RetrieveProducts(int productId) { using (NorthwindDataContext database = new NorthwindDataContext()) { return database.Products.Where(product => product.ProductID == productId) .ToArray(); } } LINQ to SQL goes through above steps to translate and execute the query. Fortunately, there is a built-in way to cache the translated query. Compiled query When such a LINQ to SQL query is executed repeatedly, The CompiledQuery can be used to translate query for one time, and execute for multiple times:internal static class CompiledQueries { private static readonly Func<NorthwindDataContext, int, Product[]> _retrieveProducts = CompiledQuery.Compile((NorthwindDataContext database, int productId) => database.Products.Where(product => product.ProductID == productId).ToArray()); internal static Product[] RetrieveProducts( this NorthwindDataContext database, int productId) { return _retrieveProducts(database, productId); } } The new version of RetrieveProducts() gets better performance, because only when _retrieveProducts is first time invoked, it internally invokes SqlProvider.Compile() to translate the query expression. And it also uses lock to make sure translating once in multi-threading scenarios. Static SQL / stored procedures without translating Another way to avoid the translating overhead is to use static SQL or stored procedures, just as the above examples. Because this is a functional programming series, this article not dive into. For the details, Scott Guthrie already has some excellent articles: LINQ to SQL (Part 6: Retrieving Data Using Stored Procedures) LINQ to SQL (Part 7: Updating our Database using Stored Procedures) LINQ to SQL (Part 8: Executing Custom SQL Expressions) Data changing overhead By looking into the data updating process, it also needs a lot of work: Begins transaction Processes the changes (ChangeProcessor) Walks through the objects to identify the changes Determines the order of the changes Executes the changings LINQ queries may be needed to execute the changings, like the first example in this article, an object needs to be retrieved before changed, then the above whole process of data retrieving will be went through If there is user customization, it will be executed, for example, a table’s INSERT / UPDATE / DELETE can be customized in the O/R designer It is important to keep these overhead in mind. Bulk deleting / updating Another thing to be aware is the bulk deleting:private static void DeleteProducts(int categoryId) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.DeleteAllOnSubmit( database.Products.Where(product => product.CategoryID == categoryId)); database.SubmitChanges(); } } The expected SQL should be like:BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 COMMIT TRANSACTION Hoverer, as fore mentioned, the actual SQL is to retrieving the entities, and then delete them one by one:-- Retrieves the entities to be deleted: exec sp_executesql N'SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 -- Deletes the retrieved entities one by one: BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=78,@p1=N'Optimus Prime',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=79,@p1=N'Bumble Bee',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 -- ... COMMIT TRANSACTION And the same to the bulk updating. This is really not effective and need to be aware. Here is already some solutions from the Internet, like this one. The idea is wrap the above SELECT statement into a INNER JOIN:exec sp_executesql N'DELETE [dbo].[Products] FROM [dbo].[Products] AS [j0] INNER JOIN ( SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0) AS [j1] ON ([j0].[ProductID] = [j1].[[Products])', -- The Primary Key N'@p0 int',@p0=9 Query plan overhead The last thing is about the SQL Server query plan. Before .NET 4.0, LINQ to SQL has an issue (not sure if it is a bug). LINQ to SQL internally uses ADO.NET, but it does not set the SqlParameter.Size for a variable-length argument, like argument of NVARCHAR type, etc. So for two queries with the same SQL but different argument length:using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.Where(product => product.ProductName == "A") .Select(product => product.ProductID).ToArray(); // The same SQL and argument type, different argument length. database.Products.Where(product => product.ProductName == "AA") .Select(product => product.ProductID).ToArray(); } Pay attention to the argument length in the translated SQL:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(1)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(2)',@p0=N'AA' Here is the overhead: The first query’s query plan cache is not reused by the second one:SELECT sys.syscacheobjects.cacheobjtype, sys.dm_exec_cached_plans.usecounts, sys.syscacheobjects.[sql] FROM sys.syscacheobjects INNER JOIN sys.dm_exec_cached_plans ON sys.syscacheobjects.bucketid = sys.dm_exec_cached_plans.bucketid; They actually use different query plans. Again, pay attention to the argument length in the [sql] column (@p0 nvarchar(2) / @p0 nvarchar(1)). Fortunately, in .NET 4.0 this is fixed:internal static class SqlTypeSystem { private abstract class ProviderBase : TypeSystemProvider { protected int? GetLargestDeclarableSize(SqlType declaredType) { SqlDbType sqlDbType = declaredType.SqlDbType; if (sqlDbType <= SqlDbType.Image) { switch (sqlDbType) { case SqlDbType.Binary: case SqlDbType.Image: return 8000; } return null; } if (sqlDbType == SqlDbType.NVarChar) { return 4000; // Max length for NVARCHAR. } if (sqlDbType != SqlDbType.VarChar) { return null; } return 8000; } } } In this above example, the translated SQL becomes:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'AA' So that they reuses the same query plan cache: Now the [usecounts] column is 2.

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  • Museum of Modern Art Starts Video Game Collection; Acquires Myst, Pac-Man, and More

    - by Jason Fitzpatrick
    The Museum of Modern Art is weighing in on the video-games-as-art debate by starting a collection of iconic video games and putting them up for public display. Read on to see what games are included in the initial batch and the MoMA’s reasons behind starting a video game collection. Although the MoMA is slated to grow to over 40 titles, the seed batch is 14 titles including: Pac-Man, Tetris, Sim City 2000, Myst, Portal, and Dwarf Fortress. In the announcement they explain the motivation for building a video game collection: Are video games art? They sure are, but they are also design, and a design approach is what we chose for this new foray into this universe. The games are selected as outstanding examples of interaction design—a field that MoMA has already explored and collected extensively, and one of the most important and oft-discussed expressions of contemporary design creativity. Our criteria, therefore, emphasize not only the visual quality and aesthetic experience of each game, but also the many other aspects—from the elegance of the code to the design of the player’s behavior—that pertain to interaction design. In order to develop an even stronger curatorial stance, over the past year and a half we have sought the advice of scholars, digital conservation and legal experts, historians, and critics, all of whom helped us refine not only the criteria and the wish list, but also the issues of acquisition, display, and conservation of digital artifacts that are made even more complex by the games’ interactive nature. This acquisition allows the Museum to study, preserve, and exhibit video games as part of its Architecture and Design collection. The above quote is only a small snippet of a much lengthier look at the benefits of examining and preserving video games, hit up the link below to check out the full post including future titles the MoMA would like to include in their archive. Video Games: 14 in the Collection, for Starters [Inside/Out] How To Boot Your Android Phone or Tablet Into Safe Mode HTG Explains: Does Your Android Phone Need an Antivirus? How To Use USB Drives With the Nexus 7 and Other Android Devices

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  • Oracle Database 11g bevet&eacute;s k&ouml;zben: Val&oacute;s felhaszn&aacute;l&oacute;i tapasztalatok

    - by Lajos Sárecz
    Tavaly tartott Magyarországon is Upgrade Workshop-ot Mike Dietrich, aki az alábbi videóban néhány érdekes ügyfél sztorit oszt meg azzal kapcsolatban, miért érdemes Oracle Database 11g-re váltani, milyen elonyei származtak azoknak az ügyfeleknek, akik már túl vannak az upgrade folyamatán. Ha nem elég meggyozoek a külföldi példák, akkor 3 hét múlva a HOUG Konferencia “Korszeru adatközpontok” szekciójában magyar ügyfelek 11g upgrade történetei is megismerhetok lesznek.

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  • Is it okay for programmers to be given the task of outlining database requirements?

    - by L'Ingenu
    In my current job, dba's and programmers are divided in tasks. Any code that needs to be written in procedures dba's write, and programmers do only application code. The strange thing is that whenever a task needs to be defined/specced, programmers get the task, and we have to define all the procedures needed and what they should return. Is this a common practice in software development? Are programmers generally the ones tasked with building requirements for the database side?

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  • How can I test database access methods in Java?

    - by javaStudent
    I want to write a test for a method that accesses a database such as following. public class MyClass{ public String getAddress(Int id){ String query = "Select * from Address where id="+id; //some additional statements resultSet = statement.executeQuery(); return result.getString(ADDRESS); } } How can I test this method? I am using Java.

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  • Capture a Query Executed By An Application Or User Against a SQL Server Database in Less Than a Minute

    - by Compudicted
    At times a Database Administrator, or even a developer is required to wear a spy’s hat. This necessity oftentimes is dictated by a need to take a glimpse into a black-box application for reasons varying from a performance issue to an unauthorized access to data or resources, or as in my most recent case, a closed source custom application that was abandoned by a deserted contractor without source code. It may not be news or unknown to most IT people that SQL Server has always provided means of back-door access to everything connecting to its database. This indispensible tool is SQL Server Profiler. This “gem” is always quietly sitting in the Start – Programs – SQL Server <product version> – Performance Tools folder (yes, it is for performance analysis mostly, but not limited to) ready to help you! So, to the action, let’s start it up. Once ready click on the File – New Trace button, or using Ctrl-N with your keyboard. The standard connection dialog you have seen in SSMS comes up where you connect the standard way: One side note here, you will be able to connect only if your account belongs to the sysadmin or alter trace fixed server role. Upon a successful connection you must be able to see this initial dialog: At this stage I will give a hint: you will have a wide variety of predefined templates: But to shorten your time to results you would need to opt for using the TSQL_Grouped template. Now you need to set it up. In some cases, you will know the principal’s login name (account) that needs to be monitored in advance, and in some (like in mine), you will not. But it is VERY helpful to monitor just a particular account to minimize the amount of results returned. So if you know it you can already go to the Event Section tab, then click the Column Filters button which would bring a dialog below where you key in the account being monitored without any mask (or whildcard):  If you do not know the principal name then you will need to poke around and look around for things like a config file where (typically!) the connection string is fully exposed. That was the case in my situation, an application had an app.config (XML) file with the connection string in it not encrypted: This made my endeavor very easy. So after I entered the account to monitor I clicked on Run button and also started my black-box application. Voilà, in a under a minute of time I had the SQL statement captured:

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  • Will loading meta tags dynamically from a database hurt the site?

    - by Nalaka526
    I have a website (ASP.NET MVC) which has its contents mainly in Sinhala language. So the search engines will list my site only when someone searches for Sinhala words. But,I need to list my site's pages in search results when searched with appropriate English words too. So I'm planning to save HTML meta tags (in English) in database and load them dynamically with appropriate page contents. Will loading the meta tags dynamically affect the site adversely?

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