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  • Creating a Group of Groups in Django

    - by Greg
    I'm creating my own Group model; I'm not referring to the builtin Group model. I want each hroup to be a member of another group (it's parent), but there is the one "top" group that doesn't have a parent group. The admin interface won't let me create a group without entering a parent. I get the error personnel_group.parent_id may not be NULL. My Group model looks like this: class Group(models.Model): name = models.CharField(max_length=50) parent = models.ForeignKey('self', blank=True, null=True) order = models.IntegerField() icon = models.ImageField(upload_to='groups', blank=True, null=True) description = models.TextField(blank=True, null=True) How can I accomplish this? Thanks.

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  • Select where and where not

    - by Simon
    I have a table containing lessons that I called "cours" (french) and I have several cours inside and I have linked them to students with a table between them to see if they go to the lessons or not. I would like to return data with the SELECT and the data that are NOT select. So, If one student follow 3 courses of 5, I would like to return the 3 courses that he follow and the 2 courses that he doesn't follow. Is there a way to do it ?

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  • Using NULLs in matchup table

    - by TomWilsonFL
    I am working on the accounting portion of a reservation system (think limo company). In the system there are multiple objects that can either be paid or submit a payment. I am tracking all of these "transactions" in three tables called: tx, tx_cc, and tx_ch. tx generates a new tx_id (for transaction ID) and keeps the information about amount, validity, etc. Tx_cc and tx_ch keep the information about the credit card or check used, respectively, which link to other tables (credit_card and bank_account among others). This seems fairly normalized to me, no? Now here is my problem: The payment transaction can take place for a myriad of reasons. Either a reservation is being paid for, a travel agent that booked a reservation is being paid, a driver is being paid, etc. This results in multiple tables, one for each of the entities: agent_tx, driver_tx, reservation_tx, etc. They look like this: CREATE TABLE IF NOT EXISTS `driver_tx` ( `tx_id` int(10) unsigned zerofill NOT NULL, `driver_id` int(11) NOT NULL, `reservation_id` int(11) default NULL, `reservation_item_id` int(11) default NULL, PRIMARY KEY (`tx_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Now this transaction is for a driver, but could be applied to an individual item on the reservation or the entire reservation overall. Therefore I demand either reservation_id OR reservation_item_id to be null. In the future there may be other things which a driver is paid for, which I would also add to this table, defaulting to null. What is the rule on this? Opinion? Obviously I could break this out into MANY three column tables, but the amount of OUTER JOINing needed seems outrageous. Your input is appreciated. Peace, Tom

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  • Syntax for "RETURNING" clause in Mysql PDO

    - by dmontain
    I'm trying to add a record, and at the same time return the id of that record added. I read it's possible to do it with a RETURNING clause. $stmt->prepare("INSERT INTO tablename (field1, field2) VALUES (:value1, :value2) RETURNING id"); but the insertion fails when I add RETURNING. There is an auto-incremented field called id in the table being added to. Can someone see anything wrong with my syntax? or maybe PDO does not support RETURNING?

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  • Join Where Rows Don't Exist or Where Criteria Matches...?

    - by Greg
    I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of Unions. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid Order: OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI Promo: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 PromoPackage: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 Desired Result: OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0

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  • Performance of VIEW vs. SQL statement

    - by Matt W.
    I have a query that goes something like the following: select <field list> from <table list> where <join conditions> and <condition list> and PrimaryKey in (select PrimaryKey from <table list> where <join list> and <condition list>) and PrimaryKey not in (select PrimaryKey from <table list> where <join list> and <condition list>) The sub-select queries both have multiple sub-select queries of their own that I'm not showing so as not to clutter the statement. One of the developers on my team thinks a view would be better. I disagree in that the SQL statement uses variables passed in by the program (based on the user's login Id). Are there any hard and fast rules on when a view should be used vs. using a SQL statement? What kind of performance gain issues are there in running SQL statements on their own against regular tables vs. against views. (Note that all the joins / where conditions are against indexed columns, so that shouldn't be an issue.) EDIT for clarification... Here's the query I'm working with: select obj_id from object where obj_id in( (select distinct(sec_id) from security where sec_type_id = 494 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) and sec_obj_id in ( select obj_id from object where obj_ot_id in (select of_ot_id from obj_form left outer join obj_type on ot_id = of_ot_id where ot_app_id = 87 and of_id in (select sec_obj_id from security where sec_type_id = 493 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) ) and of_usage_type_id = 131 ) ) ) ) or (obj_ot_id in (select of_ot_id from obj_form left outer join obj_type on ot_id = of_ot_id where ot_app_id = 87 and of_id in (select sec_obj_id from security where sec_type_id = 493 and ( (sec_usergroup_id = 3278 and sec_usergroup_type_id = 230) or (sec_usergroup_id in (select ug_gi_id from user_group where ug_ui_id = 3278) and sec_usergroup_type_id = 231) ) ) and of_usage_type_id = 131 ) and obj_id not in (select sec_obj_id from security where sec_type_id = 494) )

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  • Creating Two Cascading Foreign Keys Against Same Target Table/Col

    - by alram
    I have the following tables: user (userid int [pk], name varchar(50)) action (actionid int [pk], description nvarchar(50)) being referenced by another table that captures the relationship: <user1> <action>'s <user2>. I did this with the following table: userAction (userActionId int [pk], actionid int [fk: action.actionid], **userId1 int [fk ref's user.userid; on del/update cascade], userId2 int [fk ref's user.userid; on del/update cascade]**). However, when I try to save the userAction table i get an error because I have two cascading fk's against user.userid. Is there any way to remedy this or must I use a trigger?

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  • PHP mySQL - replace some string inside string

    - by apis17
    i want to replace ALL comma , into ,<space> in all address table in my mysql table. For example, +----------------+----------------+ | Name | Address | +----------------+----------------+ | Someone name | A1,Street Name | +----------------+----------------+ Into +----------------+----------------+ | Name | Address | +----------------+----------------+ | Someone name | A1, Street Name| +----------------+----------------+ Thanks in advance.

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  • When using a HiLo ID generation strategy, what types should be used to hold Ids?

    - by UpTheCreek
    I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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  • MySQL: automatic rollback on transaction failure

    - by praksant
    Is there any way to set MySQL to rollback any transaction on first error/warning automatically? Now if everything goes well, it commits, but on failure it leaves transaction open and on another start of transaction it commits incomplete changes from failed transaction. (I'm executing queries from php, but i don't want to check in php for failure, as it would make more calls between mysql server and webserver.) Thank you

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  • Hierarchical Hibernate, how many queries are executed?

    - by ghost1
    So I've been dealing with a home brew DB framework that has some seriously flaws, the justification for use being that not using an ORM will save on the number of queries executed. If I'm selecting all possibile records from the top level of a joinable object hierarchy, how many separate calls to the DB will be made when using an ORM (such as Hibernate)? I feel like calling bullshit on this, as joinable entities should be brought down in one query , right? Am I missing something here? note: lazy initialization doesn't matter in this scenario as all records will be used.

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  • why is there extra using where in execution plan of query

    - by user366534
    I see plan of query: EXPLAIN SELECT * FROM `subscribers` WHERE state =4 AND date_added < '2010-12-23 11:47:45' It shows: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subscribers range state_date_added state_date_added 9 NULL 8 Using where Here is indexes of table: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment subscribers 0 PRIMARY 1 subscriber_id A 382039 NULL NULL BTREE subscribers 0 email_list_id 1 email_address A 191019 NULL NULL BTREE subscribers 0 email_list_id 2 list_id A 382039 NULL NULL BTREE subscribers 1 FK_list_id 1 list_id A 10 NULL NULL BTREE subscribers 1 state_date_added 1 state A 12 NULL NULL BTREE subscribers 1 state_date_added 2 date_added A 8128 NULL NULL BTREE The last two lines describes index what is supposed for the query. Why is there in extra column using where? Even If I fetch only state and date_added column, it has in extra column: Using where; Using index. I understand why it has using index, but I don't understand Using where here.

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  • In a star schema, are foreign key constraints between facts and dimensions neccessary?

    - by Garett
    I'm getting my first exposure to data warehousing, and I’m wondering is it necessary to have foreign key constraints between facts and dimensions. Are there any major downsides for not having them? I’m currently working with a relational star schema. In traditional applications I’m used to having them, but I started to wonder if they were needed in this case. I’m currently working in a SQL Server 2005 environment.

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  • What is the best design for these data base tables?

    - by Mohammed Jamal
    I need to find the best solution to make the DB Normalized with large amount of data expected. My site has a Table Tags (contain key word,id) and also 4 types of data related to this tags table like(articles,resources,jobs,...). The big question is:- for the relation with tags what best solution for optimazaion & query speed? make a table for each relation like: table articlesToTags(ArticleID,TagID) table jobsToTags(jobid,tagid) etc. or put it all in one table like table tagsrelation(tagid,itemid,itemtype) I need your help. Please provide me with articles to help me in this design consider that in future the site can conation new section relate to tag Thanks

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  • What is the most efficient procedure for implementing a sortable ajax list on the backend?

    - by HenryL
    The most common method is to assign a sequential order field for each item in the list and do an update that maintains the sequence with every ajax sort operation. Unfortunately, this requires an update to each item of the list every time someone sorts. This is fine for small lists, but what's the best way to implement sorting for larger lists that are constantly updated? I am looking for something that minimizes DB IO.

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  • Building a wiki like data model in rails question.

    - by lillq
    I have a data model in which I would like to have an item that has a description that can be edited. I would like to also keep track of all edits to the item. I am running into issues with my current strategy, which is: class Item < ActiveRecord::Base has_one :current_edit, :class_name => "Edit", :foreign_key => "current_edit_id" has_many :edits end class Edit < ActiveRecord::Base belongs_to :item end Can the Item have multiple associations to the same class like this? I was thinking that I should switch to keeping track of the edit version in the Edit object and then just sorting the has_many relationship base on this version.

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  • PostgreSQL - select only when specific multiple apperance in column

    - by Horse SMith
    I'm using PostgreSQL. I have a table with 3 fields person, recipe and ingredient person = creator of the recipe recipe = the recipe ingredient = one of the ingredients in the recipe I want to create a query which results in every person who whenever has added carrot to a recipe, the person must also have added salt to the same recipe. More than one person can have created the recipe, in which case the person who added the ingredient will be credited for adding the ingredient. Sometimes the ingredient is used more than once, even by the same person. If this the table: person1, rec1, carrot person1, rec1, salt person1, rec1, salt person1, rec2, salt person1, rec2, pepper person2, rec1, carrot person2, rec1, salt person2, rec2, carrot person2, rec2, pepper person3, rec1, sugar person3, rec1, carrot Then I want this result: person1 Because this person is the only one who whenever has added carrot also have added salt.

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  • Maximum Row in DBMS

    - by Am1rr3zA
    Is there any limit to maximum row of table in DBMS (specially MySQL)? I want create table for saving logfile and it's row increase so fast I want know what shoud I do to prevent any problem.

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