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  • New features in SQL Prompt 6.4

    - by Tom Crossman
    We’re pleased to announce a new beta version of SQL Prompt. We’ve been trying out a few new core technologies, and used them to add features and bug fixes suggested by users on the SQL Prompt forum and suggestions forum. You can download the SQL Prompt 6.4 beta here (zip file). Let us know what you think! New features Execute current statement In a query window, you can now execute the SQL statement under your cursor by pressing Shift + F5. For example, if you have a query containing two statements and your cursor is placed on the second statement: When you press Shift + F5, only the second statement is executed:   Insert semicolons You can now use SQL Prompt to automatically insert missing semicolons after each statement in a query. To insert semicolons, go to the SQL Prompt menu and click Insert Semicolons. Alternatively, hold Ctrl and press B then C. BEGIN…END block highlighting When you place your cursor over a BEGIN or END keyword, SQL Prompt now automatically highlights the matching keyword: Rename variables and aliases You can now use SQL Prompt to rename all occurrences of a variable or alias in a query. To rename a variable or alias, place your cursor over an instance of the variable or alias you want to rename and press F2: Improved loading dialog box The database loading dialog box now shows actual progress, and you can cancel loading databases:   Single suggestion improvement SQL Prompt no longer suggests keywords if the keyword has been typed and no other suggestions exist. Performance improvement SQL Prompt now has less impact on Management Studio start up time. What do you think? We want to hear your feedback about the beta. If you have any suggestions, or bugs to report, tell us on the SQL Prompt forum or our suggestions forum.

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  • Is there a secure way to add a database troubleshooting page to an application?

    - by Josh Yeager
    My team makes a product (business management software) that our customers install on their own servers. The product uses a SQL database for data storage and app configuration. There have been quite a few cases where something strange happened in the customer's database (caused by bugs in our app and also sometimes admins who mess with the database). To figure out what is wrong with the data, we have to send SQL scripts to the customer and tell them how to run them on the database server. Then, once we know how to fix it, we have to send another script to repair the data. Is there a secure way to add a page in our application that allows an application admin to enter SQL scripts that read and write directly to the database? Our support team could use that to help customers run these scripts, without needing direct access to the SQL server. My big concerns are that someone might abuse this power to get data they shouldn't have and maybe to erase or modify data that they shouldn't be able to modify. I'm not worried about system admins, because they could find another way to do the same thing. But what if someone else got access to the form? Is there any way to do this kind of thing securely?

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  • Should I close database connections after use in PHP?

    - by Sprottenwels
    I wonder if I should close any unnecessary database connection inside of my PHP scripts. I am aware of the fact that database connections are closed implicitly when the block stops executing and 'manually' closing the connections could kinda bloat the codebase with unnecessary code. But shouldn't I do so in order to make by code as readable and as easy understandable as possible, while also preventing several possible issues during run time? Also, if I would do, would it be enough to unset() my database object?

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  • Beta Opportunity Soon to Close on "Oracle Database 12c: Installation and Administration" (1Z0-062)

    - by Brandye Barrington
    This is your last opportunity to take the "Oracle Database 12c: Installation and Administration" (1Z1-062) beta exam at the greatly discounted rate of $50 USD, as well as be one of the first to hold this new OCA certification. Earning the Oracle Database 12c Administrator Certified Associate credential gives you the foundational knowledge and skills needed to administer the Oracle Database and sets the stage for your future progression to Oracle Database 12c Administrator Certified Professional.  You can get all preparation details, including exam objectives, number of questions, time allotments, and pricing on the Oracle Certification website. Visit pearsonvue.com/oracle and register for exam 1Z1-062. QUICK LINKS: Certification Track: Oracle Database 12c Administrator Certified Associate Certification Exam: "Oracle Database 12c: Installation and Administration" (1Z1-062) Recommended Training: Oracle Database 12c: Admin, Install and Upgrade Accelerated, Oracle Database 12c: Install and Upgrade Workshop, or Oracle Database 12c: Administration Workshop Certification Website: About Beta Exams Register Now: Pearson VUE

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  • For an ORM supporting data validation, should constraints be enforced in the database as well?

    - by Ramnique Singh
    I have always applied constraints at the database level in addition to my (ActiveRecord) models. But I've been wondering if this is really required? A little background I recently had to unit test a basic automated timestamp generation method for a model. Normally, the test would create an instance of the model and save it without validation. But there are other required fields that aren't nullable at the in the table definition, meaning I cant save the instance even if I skip the ActiveRecord validation. So I'm thinking if I should remove such constraints from the db itself, and let the ORM handle them? Possible advantages if I skip constraints in db, imo - Can modify a validation rule in the model, without having to migrate the database. Can skip validation in testing. Possible disadvantage? If its possible that ORM validation fails or is bypassed, howsoever, the database does not check for constraints. What do you think? EDIT In this case, I'm using the Yii Framework, which generates the model from the database, hence database rules are generated also (though I could always write them post-generation myself too).

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  • Sample code from apple iPhoneMultichannelMixerTest can't run mp3 file

    - by Usman
    Hi i want to control channel volume from my app and iPhoneMultichannelMixerTest (http://developer.apple.com/iphone/library/samplecode/iPhoneMultichannelMixerTest/)sample code form apple looks perfect for me. but i m heaving problem in playing mp3 files. code crashes in MultichannelMixerController.m at static OSStatus renderInput(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) { SoundBufferPtr sndbuf = (SoundBufferPtr)inRefCon; UInt32 bufSamples = sndbuf[inBusNumber].numFrames; AudioUnitSampleType *in = sndbuf[inBusNumber].data; AudioUnitSampleType *outA = (AudioUnitSampleType *)ioData->mBuffers[0].mData; AudioUnitSampleType *outB = (AudioUnitSampleType *)ioData->mBuffers[1].mData; UInt32 sample = sndbuf[inBusNumber].sampleNum; for (UInt32 i = 0; i < inNumberFrames; ++i) { if (1 == inBusNumber) { outA[i] = 0; outB[i] = in[sample++]; //crash on this line. } else { outA[i] = in[sample++]; outB[i] = 0; } if (sample >= bufSamples) sample = 0; } sndbuf[inBusNumber].sampleNum = sample; // printf("bus %d sample %d\n", inBusNumber, sample); return noErr; } can any one tell me why this is happening. or is there any limitation to play mp3 on iPhone??? Thankz in Adv. Usman

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  • Error while configuring Sql server 2005 for full text search

    - by San
    I am trying to index a table for full text search on a SQL server 2005. When I select the change tracking as Automatic and click on the next button, I get the following error TITLE: Microsoft SQL Server This wizard will close because it encountered the following error: For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server+Management+Studio&ProdVer=9.00.4035.00&EvtSrc=Microsoft.SqlServer.Management.UI.WizardFrameworkErrorSR&EvtID=UncaughtException&LinkId=20476 ------------------------------ ADDITIONAL INFORMATION: Failed to retrieve data for this request. (Microsoft.SqlServer.SmoEnum) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&LinkId=20476 An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) The EXECUTE permission was denied on the object 'sp_help_category', database 'msdb', schema 'dbo'. The SELECT permission was denied on the object 'sysjobs_view', database 'msdb', schema 'dbo'. (Microsoft SQL Server, Error: 229) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.4035&EvtSrc=MSSQLServer&EvtID=229&LinkId=20476 ------------------------------ BUTTONS: OK

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  • Configuring Sql server 2005 for full text search

    - by San
    I am trying to index a table for full text search on a SQL server 2005. When I select the change tracking as Automatic and click on the next button, I get the following error TITLE: Microsoft SQL Server This wizard will close because it encountered the following error: For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server+Management+Studio&ProdVer=9.00.4035.00&EvtSrc=Microsoft.SqlServer.Management.UI.WizardFrameworkErrorSR&EvtID=UncaughtException&LinkId=20476 ------------------------------ ADDITIONAL INFORMATION: Failed to retrieve data for this request. (Microsoft.SqlServer.SmoEnum) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&LinkId=20476 An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) The EXECUTE permission was denied on the object 'sp_help_category', database 'msdb', schema 'dbo'. The SELECT permission was denied on the object 'sysjobs_view', database 'msdb', schema 'dbo'. (Microsoft SQL Server, Error: 229) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.4035&EvtSrc=MSSQLServer&EvtID=229&LinkId=20476 ------------------------------ BUTTONS: OK

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  • Linked Server related

    - by rmdussa
    I have two instances of SQL Server: Server1 (SQL Server 2008) Server2 (SQL Server 2005) I am executing a stored procedure from Server1 which references tables on Server2. It is working fine in my test environment: Server1 runs Vista SP2, SQL Server 2008; Server2 runs Windows XP SP2, SQL Server 2005. However, it is not working in the production environment: Server1 runs Vista SP1, SQL Server 2008; Server2 runs Windows XP SP2, SQL Server 2005. The error message I receive is: OLE DB provider "SQLNCLI10" for linked server "Server2" returned message "No transaction is active.". Msg 7391, Level 16, State 2, Line 21 The operation could not be performed because OLE DB provider "SQLNCLI10" for linked server "Server2" was unable to begin a distributed transaction.

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  • How SqlDataAdapter works internally?

    - by tigrou
    I wonder how SqlDataAdapter works internally, especially when using UpdateCommand for updating a huge DataTable (since it's usually a lot faster that just sending sql statements from a loop). Here is some idea I have in mind : It creates a prepared sql statement (using SqlCommand.Prepare()) with CommandText filled and sql parameters initialized with correct sql types. Then, it loops on datarows that need to be updated, and for each record, it updates parameters values, and call SqlCommand.ExecuteNonQuery(). It creates a bunch of SqlCommand objects with everything filled inside (CommandText and sql parameters). Several SqlCommands at once are then batched to the server (depending of UpdateBatchSize). It uses some special, low level or undocumented sql driver instructions that allow to perform an update on several rows in a effecient way (rows to update would need to be provided using a special data format and a the same sql query (UpdateCommand here) would be executed against each of these rows).

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  • database scanning tools recommendation?

    - by stock99
    Lately my boss is asking me to looking into database scanners. I know very little about db scanning technology. Just wondering if it is worth to purchase tools like Sentrigo ( http://www.mcafee.com/us/about/sentrigo.aspx ) ? Does anyone have experience of using database scanner? Also, I'd like to know if there is any limitation on it. We already conducting internal OS and web scan on regular basis, by the way.

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  • Partition 500gb of database stored in SQL Server

    - by Devendra
    Hello I have 500GB of database stored in SQL Server. Because it has too big a database, it takes time to update and insert data. Now the case is that I want to partition the data. So which partitioning techniques should I use? Or is there any other technique which will improve my performance?

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  • SQL Server database filled the hard drive and freeing up space isn't possible

    - by Jon
    I have a database in SQL Server 2008 on a 1Tb hard drive and it filled the drive, there is only 4Kb free. The MDF file is 323Gb and the LDF is 653Gb. The hard disk this DB is on has no other files on it other than the MDF and LDF so it's impossible to free up any space on the drive. The main hard disk is smaller but there is enough room to transfer the MDF to that drive, in case that helps. This server is overseas at a customer site and it's not possible at the moment to add more disk space to the server. It's also not possible to delete any records because the DB is in a failed mode (due to no disk space) and it doesn't respond to most commands. The Db is currently in full recovery mode which is why the LDF file is so large. This DB really doesn't need to be in full recovery so going forward we plan on switching it to simple mode which will save us a lot of space. I also don't care about losing the LDF file, but I need all of the data. I've spent a lot of time looking for a way out of this problem but everything I've found first involves either freeing up disk space or adding more disk space, neither of which is an option at this time. I'm stuck and any help would be greatly appreciated. I get the following log when trying to switch the DB to online mode. Msg 945, Level 14, State 2, Line 3 Database 'DBNAME' cannot be opened due to inaccessible files or insufficient memory or disk space. See the SQL Server errorlog for details. Msg 5069, Level 16, State 1, Line 3 ALTER DATABASE statement failed. Msg 1101, Level 17, State 12, Line 3 Could not allocate a new page for database 'DBNAME' because of insufficient disk space in filegroup 'DEFAULT'. Create the necessary space by dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup. I've found the following solutions but none work due to having no disk space on that drive, and since the DB is in a failed state I can't run most commmands. - DBCC SHRINKFILE - can't be run because doing a 'use DBNAME' fails - Detaching the DB and then changing the location of the MDF/LDF files, this fails because the DB is in an offline mode so you can't run detach. I'm at a loss about what else to try. Thanks.

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  • Which SQL database should I run?

    - by Chris Salij
    I'm creating my first website from hand-coded scratch (just used WordPress and Drupal before) and I'm at the point where I'm setting up my database for the site. However my host has given me 4 options to choose from in the database department. MS SQL Server 2005 MySQL PostgreSQL MySQL 5 Which should I go for? From what I understand PostgreSQL is meant for smaller databases with high access times. Though to be honost I'm not quite sure.

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  • How to rename an oracle database?

    - by arthur.aoife
    Hi, I am running Oracle 11g on windows 2003. What are the steps to rename database? I had followed the steps in http://www.ordba.net/Tutorials/OracleUtilities~DBNEWID.htm but I can't get past the error, NID-00121: Database should not be open I had tried the exact steps that were mentioned in the link but still it gives me the same error. Appreciate any help, thanks in advance. Arther

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  • Restoring a DataBase

    - by jjj
    i have two deferent Servers databases connections , let say j and k .. and i have backup data file in j, i named it jtok.bak .. now , i am trying to restore a database in k from jtok.bak , the database name is kkk ... so ... is there a way to do that ?

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  • Weird TPS peaks on SQL 2005 replicated database.

    - by SuperCoolMoss
    When monitoring the Transactions/Sec using perfmon on one of my SQL2005 replicated databases - I'm seeing the TPS increase to 1000 and then immediately drop back down again - this happens every 5 seconds. I'm not sure what's causing this - is this something to do with replication? We also have asynchronous statistics set on this particular database. I've tried profiling when the users are not connected - but nothing is writing to the database. ADDED PICTURE AND BOUNTY

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  • Exchange: encrypted mail database?

    - by Matt
    For an Microsoft Exchange server, is it possible to encrypt the email database such that the sysadmin cannot see the emails? In other words, the admin would be responsible for all aspects of running the Windows server and Exchange process, but would not be able to see the contents of any one email (except those sent to him, obviously). Only another individual (e.g. company owner) would be able to see all emails contained in the database.

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  • Use the same database or replicate it for reports and web

    - by developer
    I would like to know if i have a web with a huge Database and throw expensive (in time)reports , the best way to do this is with one database for the web and a replicated one for reports, or only one for both, i'm worried that users can throw reports for 5 or more years because they need that information and the web crashes because of this.

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  • Windows 7 & Sql 2008 - set database access to normal user

    - by simon_
    I use Windows 7 & Sql Server 2008. If I run Management Studio as normal user and try to connect to database 'MyDatabase', I get this error message 'The database MyDatabase is not accessible'. I I run Management Studio per right click 'Run as administrator', then 'MyDatabase' is accessible. Where & what should I set, to be able to access MyDatabase as normal user?

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  • Adding a second table in a database

    - by MB
    Hi everyone. I used the code provided by the NoteExample from the developers doc to create a database. Now I want to add a second table to store different data. I simply "copied" the given code, but when I try to insert into the new table I get an error saying: "0ERROR/Database(370): android.database.sqlite.SQLiteException: no such table: routes: , while compiling: INSERT INTO routes(line, arrival, duration, start) VALUES(?, ?, ?, ?);" Can someone please take quick look at my DbAdapter class and give me a hint or a solution? I really don't see any problem. my code compiles without any errors.. thanks in advance! CODE: import static android.provider.BaseColumns._ID; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DbAdapter { public static final String KEY_FROM = "title"; public static final String KEY_TO = "body"; public static final String KEY_ROWID = "_id"; public static final String KEY_START = "start"; public static final String KEY_ARRIVAL = "arrival"; public static final String KEY_LINE = "line"; public static final String KEY_DURATION = "duration"; private static final String DATABASE_NAME = "data"; private static final String DATABASE_NOTESTABLE = "notes"; private static final String DATABASE_ROUTESTABLE = "routes"; private static final String TAG = "DbAdapter"; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; /** * Database creation sql statement */ private static final String DATABASE_CREATE_NOTES = "create table notes (_id integer primary key autoincrement, " + "title text not null, body text not null)"; private static final String DATABASE_CREATE_ROUTES = "create table routes (_id integer primary key autoincrement, " + "start text not null, arrival text not null, " + "line text not null, duration text not null);"; private static final int DATABASE_VERSION = 2; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE_NOTES); Log.d(TAG, "created notes table"); db.execSQL(DATABASE_CREATE_ROUTES); //CREATE LOKALTABLE db.execSQL("CREATE TABLE " + DATABASE_ROUTESTABLE + " " + "(" + _ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_START + " TEXT NOT NULL, " + KEY_ARRIVAL + " TEXT NOT NULL, " + KEY_LINE + " TEXT NOT NULL, " + KEY_DURATION + " TEXT NOT NULL"); Log.d(TAG, "created routes table"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public DbAdapter(Context ctx) { this.mCtx = ctx; } /** * Open the notes database. If it cannot be opened, try to create a new * instance of the database. If it cannot be created, throw an exception to * signal the failure * * @return this (self reference, allowing this to be chained in an * initialization call) * @throws SQLException if the database could be neither opened or created */ public DbAdapter open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); return this; } public void close() { mDbHelper.close(); } /** * Create a new note using the title and body provided. If the note is * successfully created return the new rowId for that note, otherwise return * a -1 to indicate failure. * * @param title the title of the note * @param body the body of the note * @return rowId or -1 if failed */ public long createNote(String title, String body) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FROM, title); initialValues.put(KEY_TO, body); return mDb.insert(DATABASE_NOTESTABLE, null, initialValues); } /** * Create a new route using the title and body provided. If the route is * successfully created return the new rowId for that route, otherwise return * a -1 to indicate failure. * * @param start the start time of the route * @param arrival the arrival time of the route * @param line the line number of the route * @param duration the routes duration * @return rowId or -1 if failed */ public long createRoute(String start, String arrival, String line, String duration){ ContentValues initialValues = new ContentValues(); initialValues.put(KEY_START, start); initialValues.put(KEY_ARRIVAL, arrival); initialValues.put(KEY_LINE, line); initialValues.put(KEY_DURATION, duration); return mDb.insert(DATABASE_ROUTESTABLE, null, initialValues); } /** * Delete the note with the given rowId * * @param rowId id of note to delete * @return true if deleted, false otherwise */ public boolean deleteNote(long rowId) { return mDb.delete(DATABASE_NOTESTABLE, KEY_ROWID + "=" + rowId, null) > 0; } /** * Return a Cursor over the list of all notes in the database * * @return Cursor over all notes */ public Cursor fetchAllNotes() { return mDb.query(DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, null, null, null, null, null); } /** * Return a Cursor over the list of all routes in the database * * @return Cursor over all routes */ public Cursor fetchAllRoutes() { return mDb.query(DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, null, null, null, null, null); } /** * Return a Cursor positioned at the note that matches the given rowId * * @param rowId id of note to retrieve * @return Cursor positioned to matching note, if found * @throws SQLException if note could not be found/retrieved */ public Cursor fetchNote(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Return a Cursor positioned at the route that matches the given rowId * * @param rowId id of route to retrieve * @return Cursor positioned to matching route * @throws SQLException if note could not be found/retrieved */ public Cursor fetchRoute(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Update the note using the details provided. The note to be updated is * specified using the rowId, and it is altered to use the title and body * values passed in * * @param rowId id of note to update * @param title value to set note title to * @param body value to set note body to * @return true if the note was successfully updated, false otherwise */ public boolean updateNote(long rowId, String title, String body) { ContentValues args = new ContentValues(); args.put(KEY_FROM, title); args.put(KEY_TO, body); return mDb.update(DATABASE_NOTESTABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } }

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  • How can I duplicate a SQL Server symmetric key?

    - by rlb.usa
    We have a server with a database that has a symmetric key (Database - Security - Symmetric Key). We have a backup duplicate databases that we are using as a test databases, but we don't have this key in there. How can I duplicate this symmetric key (or make a new one exactly like the old) and put it in the existing databases? It has to have the same value and key-name as the other one. This is on SQL Server 2008.

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  • What are the Options for Storing Hierarchical Data in a Relational Database?

    - by orangepips
    Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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