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• MySQL, C++: Retrieving auto-increment ID

  - by Thomas Matthews

  I have a table with an auto-incrementing ID. After inserting a new row, I would like to retrieve the new ID. I found an article that used the MySQL function LAST_INSERT_ID(). The article says to create a new query and submit it. I'm using MySQL Connector C++, Windows XP and Vista, and Visual Studio 9. Here are my questions: Is there an API, for the connector, that will fetch the ID out of the record? Does the result set, after an insert/append, contain the new ID? The LAST_INSERT_ID is MySQL specific. Is there an SQL standard method for obtaining the new ID?

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• How to Delete all data from a table which contain self referencing foreign key

  - by Shantanu Gupta

  I have a table which has employee relationship defined within itself. i.e. EmpID Name SeniorId ----------------------- 1 A NULL 2 B 1 3 C 1 4 D 3 and so on... Where Senior ID is a foreign key whose primary key table is same with refrence column EmpId I want to clear all rows from this table without removing any constraint. How can i do this? Deletion need to be performed like this 4, 3 , 2 , 1 How can I do this

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• How to update multiple rows with one single query

  - by xRobot

  I use Postgresql + PHP. Say I have this table: Books ( id, title, year ) and this array of titles in PHP: $titles = array ("bible","kafka","Book of Eli"); now I want update all rows where the title is in the $titles array above. So I need a query like this: UPDATE books SET year = '2001-11-11' WHERE title is in $titles; Is is possible with one single query ? Or do I need to use FOR loop ?

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• Is it worth caching a Dictionary for foreign key values in ASP.net?

  - by user169867

  I have a Dictionary<int, string> cached (for 20 minutes) that has ~120 ID/Name pairs for a reference table. I iterate over this collection when populating dropdown lists and I'm pretty sure this is faster than querying the DB for the full list each time. My question is more about if it makes sense to use this cached dictionary when displaying records that have a foreign key into this reference table. Say this cached reference table is a EmployeeType table. If I were to query and display a list of employee names and types should I query for EmployeeName and EmployeeTypeID and use my cached dictionary to grab the EmployeeTypeIDs name as each record is displayed or is it faster to just have the DB grab the EmployeeName and JOIN to get the EmployeeType string bypassing the cached Dictionary all together. I know both will work but I'm interested in what will perform the fastest. Thanks for any help.

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• How do these user/userParam references relate to the Customer and Account lookups?

  - by plath

  In the following code example how do the user/userParam references relate to the Customer and Account lookups and what is the relationship between Customer and Account? // PersistenceManager pm = ...; Transaction tx = pm.currentTransaction(); User user = userService.currentUser(); List<Account> accounts = new ArrayList<Account>(); try { tx.begin(); Query query = pm.newQuery("select from Customer " + "where user == userParam " + "parameters User userParam"); List<Customer> customers = (List<Customer>) query.execute(user); query = pm.newQuery("select from Account " + "where parent-pk == keyParam " + "parameters Key keyParam"); for (Customer customer : customers) { accounts.addAll((List<Account>) query.execute(customer.key)); } } finally { if (tx.isActive()) { tx.rollback(); } }

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• How do these user/userParam references relate to the Customer and Account lookups?

  - by marmalade

  In the following code example how do the user/userParam references relate to the Customer and Account lookups and what is the relationship between Customer and Account? // PersistenceManager pm = ...; Transaction tx = pm.currentTransaction(); User user = userService.currentUser(); List<Account> accounts = new ArrayList<Account>(); try { tx.begin(); Query query = pm.newQuery("select from Customer " + "where user == userParam " + "parameters User userParam"); List<Customer> customers = (List<Customer>) query.execute(user); query = pm.newQuery("select from Account " + "where parent-pk == keyParam " + "parameters Key keyParam"); for (Customer customer : customers) { accounts.addAll((List<Account>) query.execute(customer.key)); } } finally { if (tx.isActive()) { tx.rollback(); } }

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• I am not able to create foreign key in mysql Error 150. Please help

  - by Shantanu Gupta

  i am trying to create a foreign key in my table. But when i executes my query it shows me error 150 Error Code : 1005 Can't create table '.\vts#sql-6ec_1.frm' (errno: 150) (0 ms taken) My Queries are Query to create a foreign Key alter table `vts`.`tblguardian` add constraint `FK_tblguardian` FOREIGN KEY (`GuardianPickPointId`) REFERENCES `tblpickpoint` (`PickPointId`) Primary Key table CREATE TABLE `tblpickpoint` ( `PickPointId` int(4) NOT NULL auto_increment, `PickPointName` varchar(500) default NULL, `PickPointLabel` varchar(500) default NULL, `PickPointLatLong` varchar(100) NOT NULL, PRIMARY KEY (`PickPointId`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 CHECKSUM=1 DELAY_KEY_WRITE=1 ROW_FORMAT=DYNAMIC Foreign Key Table CREATE TABLE `tblguardian` ( `GuardianId` int(4) NOT NULL auto_increment, `GuardianName` varchar(500) default NULL, `GuardianAddress` varchar(500) default NULL, `GuardianMobilePrimary` varchar(15) NOT NULL, `GuardianMobileSecondary` varchar(15) default NULL, `GuardianPickPointId` varchar(100) default NULL, PRIMARY KEY (`GuardianId`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1

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• setting up replication in mysql pros and cons

  - by JPro

  Basically I want to setup a replication server for mysql datbase. I am completely new to this concept and appreciate any help pointing me in the right direction. If at all the slave goes down, will it effect the master in anyway? Thanks.

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• Creating SQL table using Dynamic variable name

  - by megatoast

  I want to create backup SQL tables using variable names. something along the lines of DECLARE @SQLTable Varchar(20) SET @SQLTable = 'SomeTableName' + ' ' + '20100526' SELECT * INTO quotename(@SQLTable) FROM SomeTableName but i'm getting Incorrect syntax near '@SQLTable'. It's just part of a small script for maintence so i don't have to worry about injections.

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• How do views reduce code duplication?

  - by Debuger

  Hi! I read something like this about db views: Views are incredibly powerful and useful for one reason that stands out above all the other very good reasons. They reduce code duplication. That is, in most cases, the bottom line. If a query will be used in three or more places, then a view will drastically simplify your changes if the schema or query parameters change. I once had to edit 22 stored procedures to change some query logic. If the original architecture had utilized views, then I would have had only three changes. Can anyone explain to me how it works, and maybe give me some examples? Best regards!

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• What is best tool to compare two SQL Server databases (schema and data)?

  - by tomaszs

  I would like to compare two SQL Server databases including schema (table structure) and data in tables too. What is best tool to do this?

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• Pervasive SQL german Umlauts Problem

  - by cordellcp3

  Hi there, I'm using the Pervasive SQL - ADO.NET 3.5 DataProvider for retrieving data out of the PSQL DB and I've noticed that the german umlauts (äöüÄÖÜ etc.) are not represented correctly in the PSQLDataReader, but in the Pervasive Control Center (similar to the sql management studio) the umlauts are all correct. Is there anything similar to the TSQL "SET LANGUAGE"-command? I havn't found something like that for Pervasive SQL. Googling this issue wasn't successful at all, too. Although I did find some tips with a file called upper.alt or collate.cfg, but don't know how to use this files and I coudn`t find them in my installation. (I'm totally new to Pervasive...) I hope that someone on here could help me with that. Thanks in advance

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• How do I write this GROUP BY query in MYSQL?

  - by alex

  Suppose I have a column called "fruits" I want to select all of the top fruits, ranked by fruits (and group by + count). Fruits: orange orange apple banana apple apple In this case, the select statement would return: apple, 3 orange, 2 banana, 1

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• Struggling to create correct relationships in MS Access

  - by Yandawl

  http://img714.imageshack.us/img714/7820/croppercapture1.png Basically: an award(course) has many units, which can be either optional or core(mandatory), depending on the award. So for example: the unit 'Advanced Software Engineering' maybe a core unit for the award 'Software Engineering BSc' but only an optional unit for the course 'Web Technology BSc'. I've used flags for that purpose. A student is enrolled on an award so I need to get a complete list of core and optional units (bearing in mind that a student chooses 1 out of many possible optional units). Also, these units have events, e.g, a lecture, workshop or seminar, etc. and those events have sessions or instances of events where students enrolled on that particular unit are required to attend, and those attendances are stored in a separate table to form a register. So I need a hierarchy of expanding the tables something like this I guess: Awards - Students - Units - Sessions - Attendances Any help with this would be appreciated... It's blowing my mind and I'm really close to going insane! My tutor didn't spot I'd got it wrong when I showed my original data model to him and it's due in next week! Thank you :D

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• Porting join from Oracle to Postgres

  - by Grasper

  INSERT INTO MISSION_OBJECTIVE( MSN_INT_ID, MO_INT_ID, MO_MSN_CLASS_NM, MO_MSN_CLASS_CD, MO_MSN_TYPE, MO_PRIORITY, MO_COMMENT, MO_START_DT, MO_END_DT, ASP_AIRSPACE_NM, MO_OBJ_LOCATION, MO_ALO_LEG_ID, MO_ALO_ARRIVE_LOC) SELECT '1025', '1', 'AIRDROP', 'ADP', 'LAPES', NULL, COALESCE( NULL, ' '), TO_TIMESTAMP( '1002260900', 'YYMMDDHH24MI'), TO_TIMESTAMP( '1002260915', 'YYMMDDHH24MI'), 'TRANSIT ALPHA', 'TRANSIT ALPHA', '1', 'TRANSIT ALPHA' FROM AIRSPACE ASP, apsmain .MISSION_CLASS MC WHERE ASP.ASP_AIRSPACE_NM(+)= 'TRANSIT ALPHA' AND MC.MCS_MISSION_CLASS_NAME= 'AIRDROP' AND 'TRANSIT ALPHA' IS NOT NULL Is that exactly the same as: INSERT INTO MISSION_OBJECTIVE( MSN_INT_ID, MO_INT_ID, MO_MSN_CLASS_NM, MO_MSN_CLASS_CD, MO_MSN_TYPE, MO_PRIORITY, MO_COMMENT, MO_START_DT, MO_END_DT, ASP_AIRSPACE_NM, MO_OBJ_LOCATION, MO_ALO_LEG_ID, MO_ALO_ARRIVE_LOC) SELECT '1025', '1', 'AIRDROP', 'ADP', 'LAPES', NULL, COALESCE( NULL, ' '), TO_TIMESTAMP( '1002260900', 'YYMMDDHH24MI'), TO_TIMESTAMP( '1002260915', 'YYMMDDHH24MI'), 'TRANSIT ALPHA', 'TRANSIT ALPHA', '1', 'TRANSIT ALPHA' FROM AIRSPACE ASP, apsmain .MISSION_CLASS MC WHERE ASP.ASP_AIRSPACE_NM = 'TRANSIT ALPHA' AND MC.MCS_MISSION_CLASS_NAME= 'AIRDROP' AND 'TRANSIT ALPHA' IS NOT NULL I just deleted the (+). The part that is confusing me is that ASP.ASP_AIRSPACE_NM is being right joined to a constant.

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• Erlang Mnesia Equivalent of SQL Select FROM WHERE Field IN (value1, value2, value3, ...)

  - by ErJab

  I have an mnesia table with fields say f1, f2, f3. Now if I were to select all the rows with the field value as V1, I would use mnesia:select and match specifications or a simple mnesia:match_object. Now I need to select all the rows which have V1, V2, V3 ... or Vn (a list of arbitrary length) as the value for field f1. In SQL I would do something like SELECT * FROM tablename WHERE f3 IN (V1, V2, V3, ... , Vn) How do I do this in mnesia?

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• Implementing Model-level caching

  - by Byron

  I was posting some comments in a related question about MVC caching and some questions about actual implementation came up. How does one implement a Model-level cache that works transparently without the developer needing to manually cache, yet still remains efficient? I would keep my caching responsibilities firmly within the model. It is none of the controller's or view's business where the model is getting data. All they care about is that when data is requested, data is provided - this is how the MVC paradigm is supposed to work. (Source: Post by Jarrod) The reason I am skeptical is because caching should usually not be done unless there is a real need, and shouldn't be done for things like search results. So somehow the Model itself has to know whether or not the SELECT statement being issued to it worthy of being cached. Wouldn't the Model have to be astronomically smart, and/or store statistics of what is being most often queried over a long period of time in order to accurately make a decision? And wouldn't the overhead of all this make the caching useless anyway? Also, how would you uniquely identify a query from another query (or more accurately, a resultset from another resultset)? What about if you're using prepared statements, with only the parameters changing according to user input? Another poster said this: I would suggest using the md5 hash of your query combined with a serialized version of your input arguments. This would require twice the number of serialization options. I was under the impression that serialization was quite expensive, and for large inputs this might be even worse than just re-querying. And is the minuscule chance of collision worth worrying about? Conceptually, caching in the Model seems like a good idea to me, but it seems in practicality the developer should have direct control over caching and write it into the controller. Thoughts/ideas? Edit: I'm using PHP and MySQL if that helps to narrow your focus.

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• Using a table-alias in Kohana queries?

  - by Aristotle

  I'm trying to run a simple query with $this->db in Kohana, but am running into some syntax issues when I try to use an alias for a table within my query: $result = $this->db ->select("ci.chapter_id, ci.book_id, ci.chapter_heading, ci.chapter_number") ->from("chapter_info ci") ->where(array("ci.chapter_number" => $chapter, "ci.book_id" => $book)) ->get(); It seems to me that this should work just fine. I'm stating that "chapter_info" ought to be known as "ci," yet this isn't taking for some reason. The error is pretty straight-forward: There was an SQL error: Table 'gb_data.chapter_info ci' doesn't exist - SELECT `ci`.`chapter_id`, `ci`.`book_id`, `ci`.`chapter_heading`, `ci`.`chapter_number` FROM (`chapter_info ci`) WHERE `ci`.`chapter_number` = 1 AND `ci`.`book_id` = 1 If I use the full table name, rather than an alias, I get the expected results without error. This requires me to write much more verbose queries, which isn't ideal. Is there some way to use shorter names for tables within Kohana's query-builder?

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• correlated query /subquery VS join query

  - by trojanwarrior3000

  can we always convert a usual subquery/correlated subquery to join type query?

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• Event triggering in server-side scripts

  - by Qiao

  In SO, when your question got answer. or you got new badge, event is triggered. Or when you got new PM in forum, it also lets you know by alerting message. You see message that something happened with your account when you enter site for first time after this event. How is this implemented? How do scripts know, that they have something new to show you?

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• 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.

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• How to move an element in a sorted list and keep the CouchDb write "atomic"

  - by karlthorwald

  I have elements of a list in couchdb documents. Let's say these are 3 elements in 3 documents: { "id" : "783587346", "type" : "aList", "content" : "joey", "sort" : 100.0 } { "id" : "358734ff6", "type" : "aList", "content" : "jill", "sort" : 110.0 } { "id" : "abf587346", "type" : "aList", "content" : "jack", "sort" : 120.0 } A view retrieves all "aList" documents and displays them sorted by "sort". Now I want to move the elements, when I want to move "jack" to the middle, I could do this atomic in one write and change it's sort key to 105.0. The view now returns the documents in the new sort order. After a lot of sorting I could end up with sort keys like 50.99999 and 50.99998 after some years and in extreme situations run out of digits? What can you recommend, is there a better way to do this? I'd rather keep the elements in seperate documents. Different users might edit different elements in parallel (which also can get tricky). Maybe there is a much better way?

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• How to detect a pending JDO transaction?

  - by Stevko

  I believe I am getting JDO commit Exceptions due to the transactions nesting although I'm not sure. Will this detect the situation where I am starting a transaction when another is pending? PersistenceManager pm = PersistenceManagerFactory.get().getPersistenceManager(); assert pm.currentTransaction().isActive() == false : "arrrgh"; pm.currentTransaction().begin(); Is there a better or more reliable way?

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• Select count / duplicates

  - by mike

  Hello! I have a table with all U.S. zip codes. each row contains the city and state name for the zip code. I'm trying to get a list of cities that show up in multiple states. This wouldn't be a problem if there weren't X amount of zip codes in the same city... So basically, I just want to the city in a state to count as 1 instead of it counting the city/state 7 times because there are 2+ zip codes in that city/state... I'm not really sure how to do this. I know I need to use count but how do I tell the mysql to only count a given city/state combo as 1?

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• index on index ?

  - by trojanwarrior3000

  can one create index on index ? why ? an example ?

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