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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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  • Return order of MySQL SHOW COLUMNS

    - by rich
    Hey guys. Simple one this, but one I can't seem to find any information on so here goes. I need to find the columns in a specific table, which is no problem.... SHOW COLUMNS FROM tablename LIKE '%ColumnPrefix%'; But I need to know what order they will be returned, preferable by choosing to order the results ascending alphabetically. I have had no luck with using ORDER BY Field. Any ideas? Cheers!

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  • What is the most efficient/elegant way to parse a flat table into a tree?

    - by Tomalak
    Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0 20 4 'Node 1.1.1' 2 10 5 'Node 2.1' 3 10 6 'Node 1.2' 1 20 What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly intended tree? Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly. Pseudo code or plain English is okay, this is purely a conceptional question. Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS? EDITS AND ADDITIONS To answer one commenter's (Mark Bessey's) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted. The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay. The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though. Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable. I have posted my own solution so you guys can pull it to pieces.

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  • Optimum size of transaction in Postgres?

    - by Joe
    I'm running a process that does a lot of updates ( 100,000) to a table. I have the choice between putting all the updates in a single transaction or committing transactions every 1000 or so. Ignore for the moment the case where a transaction fails and is aborted. I'm interested in the best size of transaction for memory and speed efficiency.

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  • Why connection in Python's DB-API does not have "begin" operation?

    - by newtover
    Working with cursors in mysql-python I used to call "BEGIN;", "COMMIT;", and "ROLLBACK;" explicitly as follows: try: cursor.execute("BEGIN;") # some statements cursor.execute("COMMIT;") except: cursor.execute("ROLLBACK;") then, I found out that the underlying connection object has the corresponding methods: try: cursor.connection.begin() # some statements cursor.connection.commit() except: cursor.connection.rollback() Inspecting the DB-API PEP I found out that it does not mention the begin() method for the connection object, even for the extensions. Mysql-python, by the way, throws the Deprecation Warning, when you use the method. sqlite3.connection, for example, does not have the methd at all. And the question is why there is no such method in the PEP? Is the statement somehow optional, is it enough to invoke commit() instead?

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  • Jasper error: Caused by SQLServerException: Transaction (Process ID 58) was deadlocked on thread | c

    - by Saky
    I got the above error in my jasper report mail. The query that is used in the report is quite complicated (for me). Reading different posts I conclude that to solve this the I have to change the query to SET TRANSACTION ISOLATION LEVEL REPEATABLE READ GO BEGIN TRANSACTION ... my query ... COMMIT TRANSACTION ? I wonder if this is the correct way to solve the error and that if it has any side effects? Has it happened to anyone in the Jasper reports? Does anyone know if there is a better solution exist to the problem? (Although that I have not yet tested the above solution, if anyone can give any insight on this will be helpful.)

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  • Swap unique indexed column values in database.

    - by Ramesh Soni
    I have a database table and one of the fields (not primary key) is having unique index on it. Now I want to swap values under this column for two rows. How could this be done? Two hack I know are: Delete both rows and re-insert them Update rows with some other value and swap and then update to actual value. But I don't want to go for these as they do not seem to be the appropriate solution to the problem. Could anyone help me out?

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  • NULL-keys for key/value table

    - by user72185
    (Using Oracle) I have a table with key/value pairs like this: create table MESSAGE_INDEX ( KEY VARCHAR2(256) not null, VALUE VARCHAR2(4000) not null, MESSAGE_ID NUMBER not null ) I now want to find all the messages where key = 'someKey' and value is 'val1', 'val2' or 'val3' - OR value is null in which case there will be no entry in the table at all. This is to save space; there would be a large number of keys with null values if I stored them all. I think this works: SELECT message_id FROM message_index idx WHERE ((key = 'someKey' AND value IN ('val1', 'val2', 'val3')) OR NOT EXISTS (SELECT 1 FROM message_index WHERE key = 'someKey' AND idx.message_id = message_id)) But is is extremely slow. Takes 8 seconds with 700K records in message_index and there will be many more records and more search criteria when moving outside of my test environment. Primary key is key, value, message_id: add constraint PK_KEY_VALUE primary key (KEY, VALUE, MESSAGE_ID) And I added another index for message_id, to speed up searching for missing keys: create index IDX_MESSAGE_ID on MESSAGE_INDEX (MESSAGE_ID) I will be doing several of these key/value lookups in every search, not just one as shown above. So far I am doing them nested, where output id's of one level is the input to the next. E.g.: SELECT message_id from message_index WHERE (key/value compare) AND message_id IN ( SELECT ... and so on ) What can I do to speed this up?

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  • JPA native query join returns object but dereference throws class cast exception

    - by masato-san
    I'm using JPQL Native query to join table and query result is stored in List<Object[]>. public String getJoinJpqlNativeQuery() { String final SQL_JOIN = "SELECT v1.bitbit, v1.numnum, v1.someTime, t1.username, t1.anotherNum FROM MasatosanTest t1 JOIN MasatoView v1 ON v1.username = t1.username;" System.out.println("get join jpql native query is being called ============================"); EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getDefaultManager(); Query query = em.createNativeQuery(SQL_JOIN); out = query.getResultList(); System.out.println("return object ==========>" + out); System.out.println(out.get(0)); String one = out.get(0).toString(); //LINE 77 where ClassCastException System.out.println(one); } catch(Exception e) { } finally { if(em != null) { em.close; } } } The problem is System.out.println("return object ==========>" + out); outputs: return object ==========> [[true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020], [false, 0, 2010-12-21 15:32:53.0, koga, 0.213]] System.out.println(out.get(0)) outputs: [true, 0, 2010-12-21 15:32:53.0, masatosan, 0.020] So I assumed that I can assign return value of out.get(0) which should be String: String one = out.get(0).toString(); But I get weird ClassCastException. java.lang.ClassCastException: java.util.Vector cannot be cast to [Ljava.lang.Object; at local.test.jaxrs.MasatosanTestResource.getJoinJpqlNativeQuery (MasatosanTestResource.java:77) So what's really going on? Even Object[] foo = out.get(0); would throw an ClassCastException :(

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  • Many to Many Association Tables - Is it customary to put additional columns in these tables?

    - by Randy Minder
    We've encountered the following situation in our database. We have table 'A' and table 'B' which have a M2M relationship. The association table is named 'AB' and contains a FK column to table 'A' and a FK column to table 'B'. Now we've identified a need to store additional data about this association. For example, a date when the association occurred, and who made the association etc. We've decided to put these additional columns in the 'AB' association table. However, something tells me this is frowned upon by database purists. On the other hand, it makes no sense to us to create yet an additional table to store this associated data. What's the prevailing thought on this?

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  • How to optimise MySQL query containing a subquery?

    - by aidan
    I have two tables, House and Person. For any row in House, there can be 0, 1 or many corresponding rows in Person. But, of those people, a maximum of one will have a status of "ACTIVE", the others will all have a status of "CANCELLED". e.g. SELECT * FROM House LEFT JOIN Person ON House.ID = Person.HouseID House.ID | Person.ID | Person.Status 1 | 1 | CANCELLED 1 | 2 | CANCELLED 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | 4 | CANCELLED I want to filter out the cancelled rows, and get something like this: House.ID | Person.ID | Person.Status 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | NULL | NULL I've achieved this with the following sub select: SELECT * FROM House LEFT JOIN ( SELECT * FROM Person WHERE Person.Status != "CANCELLED" ) Person ON House.ID = Person.HouseID ...which works, but breaks all the indexes. Is there a better solution that doesn't? I'm using MySQL and all relevant columns are indexed. EXPLAIN lists nothing in possible_keys. Thanks.

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  • Error: A SQLParamenter wtih ParameterName @myparm is not contained by this SQLParameter Collection

    - by SidC
    Good Morning, I'm working on an ASP.NET 3.5 webforms application and have written the following code: Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click Dim connectionString As String = WebConfigurationManager.ConnectionStrings("Diel_inventoryConnectionString").ConnectionString Dim con As New SqlConnection(connectionString) Dim adapter1 As New SqlDataAdapter adapter1.SelectCommand = New SqlCommand adapter1.SelectCommand.CommandType = CommandType.StoredProcedure adapter1.SelectCommand.CommandText = "PartSproc" Dim parmNSN As New SqlParameter("@NSN", SqlDbType.NVarChar) Dim parmName As New SqlParameter("@PartName", SqlDbType.NVarChar) txtNSN.Text = adapter1.SelectCommand.Parameters("@NSN").Value txtSearch.Text = adapter1.SelectCommand.Parameters("@PartName").Value Dim dt As New DataTable() adapter1.Fill(dt) MySearch.DataSource = dt MySearch.DataBind() End Sub When I run the page, I receive the error A SQLParameter with @NSN is not contained by this SQLParameter Collection. I tried using apostrophes around the @NSN and @PartName but that does not work either and presents expression expected error. How might I rectify the above code so that it references the @NSN and @PartName parameters correctly? Thanks, Sid

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  • Best Way to Generate Unique and consecutives numbers in Oracle

    - by RRUZ
    I need to generate unique and consecutive numbers (for use on an invoice), in a fast and reliable way. currently use a Oracle sequence, but in some cases generated numbers are not consecutive because of exceptions that may occur. I thought a couple of solutions to manage this problem, but neither of they convincing me. What solution do you recommend? Use a select max () SELECT MAX (NVL (doc_num, 0)) +1 FROM invoices Use a table to store the last number generated for the invoice. UPDATE docs_numbers SET last_invoice = last_invoice + 1 Another Solution?

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  • ProviderException: InvalidCastException

    - by JS
    Few of our clients are regularly getting invalid cast exception, with variations i.e. InvalidCastException / ProviderException, but both generating from method call: System.Web.Security.SqlRoleProvider.GetRolesForUser(String username) The other variation is: Exception type: InvalidCastException Exception message: Unable to cast object of type System.Int32 to type System.String. I had a look at application event log which shows: Stack trace: at System.Web.Security.SqlRoleProvider.GetRolesForUser(String username) at System.Web.Security.RolePrincipal.IsInRole(String role) at System.Web.Configuration.AuthorizationRule.IsTheUserInAnyRole(StringCollection roles, IPrincipal principal) at System.Web.Configuration.AuthorizationRule.IsUserAllowed(IPrincipal user, String verb) at System.Web.Configuration.AuthorizationRuleCollection.IsUserAllowed(IPrincipal user, String verb) at System.Web.Security.UrlAuthorizationModule.OnEnter(Object source, EventArgs eventArgs) at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)* Has anyone come across this issue, and if so what is the fix? Thanks JS

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  • date comparisons in Rails

    - by aressidi
    Hi there, I'm having trouble with a date comparison in a named scope. I'm trying to determine if an event is current based on its start and end date. Here's the named scope I'm using which kind of works, though not for events that have the same start and end date. named_scope :date_current, :conditions => ["Date(start_date) <= ? AND Date(end_date) >= ?", Time.now, Time.now] This returns the following record, though it should return two records, not one... >> Event.date_current => [#<Event id: 2161, start_date: "2010-02-15 00:00:00", end_date: "2010-02-21 00:00:00", ...] What it's not returning is this as well >> Event.find(:last) => #<Event id: 2671, start_date: "2010-02-16 00:00:00", end_date: "2010-02-16 00:00:00", ...> The server time seems to be in UTC and I presume that the entries are being stored in the DB in UTC. Any ideas as to what I'm doing wrong or what to try? Thanks!

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  • (My)SQL performance: updating one field vs many unneccesary fields

    - by changokun
    i'm processing a form that has a lot of fields for a user who is editing an existing record. the user may have only changed one field, and i would typically do an update query that sets the values of all the fields, even though most of them don't change. i could do some sort of tracking to see which fields have actually changed, and only update the few that did. is there a performance difference between updating all fields in a record vs only the one that changed? are there other reasons to go with either method? the shotgun method is pretty easy...

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  • MS-ACCESS query to match first few characters in string comparision

    - by neobee
    What query is suitable to compare two tables specied below, however only part of string in location(table1) will matches with the Location(table2). Location(table1) Location(table2) india- north USxcs India-west Indiaasd India- east Indiaavvds India- south Africassdcasv US- north Africavasvdsa us-west UKsacvavsdv uk- east Indiacascsa uk- south UScssca Africa-middle Indiacsasca Africa-south Africaccc Africa-east UKcac only 1st two characters of location(table1) and 1st two characters of location(table2) should match. Please help only any four characters of location(table1)and any two characters of location(table2)should match.

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  • LINQ for Java tool

    - by Milhous
    Would a LINQ for java be a useful tool? I have been working on a tool that will allow a Java object to map to a row in a database. Would this be useful for Java programmers? What features would be useful?

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  • Speeding up inner-joins and subqueries while restricting row size and table membership

    - by hiffy
    I'm developing an rss feed reader that uses a bayesian filter to filter out boring blog posts. The Stream table is meant to act as a FIFO buffer from which the webapp will consume 'entries'. I use it to store the temporary relationship between entries, users and bayesian filter classifications. After a user marks an entry as read, it will be added to the metadata table (so that a user isn't presented with material they have already read), and deleted from the stream table. Every three minutes, a background process will repopulate the Stream table with new entries (i.e. whenever the daemon adds new entries after the checks the rss feeds for updates). Problem: The query I came up with is hella slow. More importantly, the Stream table only needs to hold one hundred unread entries at a time; it'll reduce duplication, make processing faster and give me some flexibility with how I display the entries. The query (takes about 9 seconds on 3600 items with no indexes): insert into stream(entry_id, user_id) select entries.id, subscriptions_users.user_id from entries inner join subscriptions_users on subscriptions_users.subscription_id = entries.subscription_id where subscriptions_users.user_id = 1 and entries.id not in (select entry_id from metadata where metadata.user_id = 1) and entries.id not in (select entry_id from stream where user_id = 1); The query explained: insert into stream all of the entries from a user's subscription list (subscriptions_users) that the user has not read (i.e. do not exist in metadata) and which do not already exist in the stream. Attempted solution: adding limit 100 to the end speeds up the query considerably, but upon repeated executions will keep on adding a different set of 100 entries that do not already exist in the table (with each successful query taking longer and longer). This is close but not quite what I wanted to do. Does anyone have any advice (nosql?) or know a more efficient way of composing the query?

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  • Entity Framework doesn't like 0..1 to * relationships.

    - by Orion Adrian
    I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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  • How to select only the first rows for each unique value of a column

    - by nuit9
    Let's say I have a table of customer addresses: CName | AddressLine ------------------------------- John Smith | 123 Nowheresville Jane Doe | 456 Evergreen Terrace John Smith | 999 Somewhereelse Joe Bloggs | 1 Second Ave In the table, one customer like John Smith can have multiple addresses. I need the select query for this table to return only first row found where there are duplicates in 'CName'. For this table it should return all rows except the 3rd (or 1st - any of those two addresses are okay but only one can be returned). Is there a keyword I can add to the SELECT query to filter based on whether the server has already seen the column value before?

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  • make multiple, composite query in oracle

    - by Meloun
    How can i make multiple, composite query in oracle? for example this several queries in one step? 1 CREATE TABLE test (id NUMBER PRIMARY KEY, name VARCHAR2(30)); 2 CREATE SEQUENCE test_sequence START WITH 1 INCREMENT BY 1; 3 CREATE OR REPLACE TRIGGER test_trigger BEFORE INSERT ON test REFERENCING NEW AS NEW FOR EACH ROW BEGIN SELECT test_sequence.nextval INTO :NEW.ID FROM dual; END; 4 INSERT INTO test (name) VALUES ('Jon'); 5 INSERT INTO test (name) VALUES ('Meloun');

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  • Cannot call scalar-valued CLR UDF from select ... from table statement

    - by Henrik B
    I have created a scalar-valued CLR UDF (user defined function). It takes a timezone id and a datetime and returns the datetime converted to that timezone. I can call it from a simple select without problems: "select dbo.udfConvert('Romance Standard Time', @datetime)" (@datetime is of course a valid datetime variable) But if I call it passing in a datetime from a table it fails: "select dbo.udfConvert('Romance Standard Time', StartTime) from sometable" (column StartTime is of course a column of type datetime) The error message is: "Cannot find either column "dbo" or the user-defined function or aggregate "dbo.udfConvert", or the name is ambiguous." This message is really for beginners that has misspelled something, but as it works in one case and not in the other, I don't think I have done any misspellings. Any ideas?

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