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  • How can I synchronize one set of data with another?

    - by RenderIn
    I have an old database and a new database. The old records were converted to the new database recently. All our old applications continue to point to the old database, but the new applications point to the new database. Currently the old database is the only one being updated, so throughout the day the new database becomes out of sync. It is acceptable for the new database to be out of sync for a day, so until all our applications are pointed to the new database I just need to write a nightly cron job that will bring it up to date. I do not want to purge the new database and run the complete conversion script each night, as that would reduce uptime and would create a mess in our auditing of that table. I'm thinking about selecting all the data from the old database, converting it to the new database structure in memory, and then checking for the existence of each record before inserting it in the new database. After that's done, I'd select everything from the new database and check if it exists in the old one, and if not delete it. Is this the simplest way to do this?

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  • How do I get the earlist DateTime of a set, where there is a few conditions

    - by radbyx
    Create script for Product SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_PADDING ON GO CREATE TABLE [dbo].[Product]( [ProductID] [int] IDENTITY(1,1) NOT NULL, [ProductName] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO Create script for StateLog SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[StateLog]( [StateLogID] [int] IDENTITY(1,1) NOT NULL, [ProductID] [int] NOT NULL, [Status] [bit] NOT NULL, [TimeStamp] [datetime] NOT NULL, CONSTRAINT [PK_Uptime] PRIMARY KEY CLUSTERED ( [StateLogID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[StateLog] WITH CHECK ADD CONSTRAINT [FK_Uptime_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Product] ([ProductID]) GO ALTER TABLE [dbo].[StateLog] CHECK CONSTRAINT [FK_Uptime_Products] GO I have this and it's not enough: select top 5 [ProductName], [TimeStamp] from [Product] inner join StateLog on [Product].ProductID = [StateLog].ProductID where [Status] = 0 order by TimeStamp desc; (My query givess the 5 lastest TimeStamp's where Status is 0(false).) But I need a thing more: Where there is a set of lastest TimeStamps for a product where Status is 0, i only want the earlist of them (not the lastet). Example: Let's say for Product X i have: TimeStamp1(status = 0) TimeStamp2(status = 1) TimeStamp3(status = 0) TimeStamp4(status = 0) TimeStamp5(status = 1) TimeStamp6(status = 0) TimeStamp7(status = 0) TimeStamp8(status = 0) Correct answer would then be:: TimeStamp6, because it's the first of the lastest timestamps.

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  • MySQL: How to copy rows, but change a few fields?

    - by Andrew
    I have a large number of rows that I would like to copy, but I need to change one field. I can select the rows that I want to copy: select * from Table where Event_ID = "120" Now I want to copy all those rows and create new rows while setting the Event_ID to 155. How can I accomplish this?

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  • Database Optimization techniques for amateurs.

    - by Zombies
    Can we get a list of basic optimization techniques going (anything from modeling to querying, creating indexes, views to query optimization). It would be nice to have a list of these, one technique per answer. As a hobbyist I would find this to be very useful, thanks. And for the sake of not being too vague, let's say we are using a maintstream DB such as MySQL or Oracle, and that the DB will contain 500,000-1m or so records across ~10 tables, some with foreign key contraints, all using the most typical storage engines (eg: InnoDB for MySQL). And of course, the basics such as PKs are defined as well as FK contraints.

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  • Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

    - by DanM
    I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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  • Database table schema design - varchar(n). Suitable choice of N

    - by morpheous
    Coming from a C background, I may be getting too anal about this and worrying unnecessarily about bits and bytes here. Still, I cant help thinking how the data is actually stored and that if I choose an N which is easily factorizable into a power of 2, the database will be more effecient in how it packs data etc. Using this "logic", I have a string field in a table which is a variable length up to 21 chars. I am tempted to use 32 instead of 21, for the reason given above - however now I am thinking that I am wasting disk space because there will be space allocated for 11 extra chars that are guaranteed to be never used. Since I envisage storing several tens of thousands of rows a day, it all adds up. Question: Mindful of all of the above, Should I declare varchar(21) or varchar(32) and why?

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  • Generating incremental numeric column values during INSERT SELECT statement

    - by Charles
    I need to copy some data from one table to another in Oracle, while generating incremental values for a numeric column in the new table. This is a once-only exercise with a trivial number of rows (100). I have an adequate solution to this problem but I'm curious to know if there is a more elegant way. I'm doing it with a temporary sequence, like so: CREATE SEQUENCE temp_seq START WITH 1; INSERT INTO new_table (new_col, copied_col1, copied_col2) SELECT temp_seq.NEXTVAL, o.* FROM (SELECT old_col1, old_col2 FROM old_table) o; DROP SEQUENCE temp_seq; Is there way to do with without creating the sequence or any other temporary object? Specifically, can this be done with a self-contained INSERT SELECT statement? There are similar questions, but I believe the specifics of my question are original to SO.

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  • How to repair "order by" after union of 2 selects from 1 tables

    - by 4e4el
    I have a dropDownList on my form, where i need to have union of values from 2 colums of table [ost]. Type of this columns is currency. I have russian version of access, default value of curency in "rur" and i need "uah". I need to change format and save "order by". I use this query: (SELECT distinct FORMAT([Sum1] ,'# ##0.00" uah.";-# ##0.00" uah."') FROM ost) Union (SELECT distinct FORMAT([Sum2],'# ##0.00" uah.";-# ##0.00" uah."') FROM ost) ORDER BY 1

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  • How to group by having the same id?

    - by simpatico
    Hello, I want the customerid who bought product X and Y and Z, from the following schema: Sales(customerid, productName, rid); I could do the intersection: select customerid from sales where productName='X' INTERSECT select customerid from sales where productName='X' INTERSTECT select customerid from sales where productName='Z' Is this the best I could do?

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  • Optimize SQL query (Facebook-like application)

    - by fabriciols
    My application is similar to Facebook, and I'm trying to optimize the query that get user records. The user records are that he as src ou dst. The src is in usermuralentry directly, the dst list are in usermuralentry_user. So, a entry can have one src and many dst. I have those tables: mysql> desc usermuralentry ; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_src_id | int(11) | NO | MUL | NULL | | | private | tinyint(1) | NO | | NULL | | | content | longtext | NO | | NULL | | | date | datetime | NO | | NULL | | | last_update | datetime | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ 10 rows in set (0.10 sec) mysql> desc usermuralentry_user ; +-------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | usermuralentry_id | int(11) | NO | MUL | NULL | | | userinfo_id | int(11) | NO | MUL | NULL | | +-------------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) And the following query to retrieve information from two users. mysql> explain SELECT * FROM usermuralentry AS a , usermuralentry_user AS b WHERE a.user_src_id IN ( 1, 2 ) OR ( a.id = b.usermuralentry_id AND b.userinfo_id IN ( 1, 2 ) ); +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | 1 | SIMPLE | b | ALL | usermuralentry_id,usermuralentry_user_bcd7114e,usermuralentry_user_6b192ca7 | NULL | NULL | NULL | 147188 | | | 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 1371289 | Range checked for each record (index map: 0x1) | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ 2 rows in set (0.00 sec) but it is taking A LOT of time... Some tips to optimize? Can the table schema be better in my application?

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  • select distinct over specific columns

    - by Midhat
    A query in a system I maintain returns QID AID DATA 1 2 x 1 2 y 5 6 t As per a new requirement, I do not want the (QID, AID)=(1,2) pair to be repeated. We also dont care what value is selected from "data" column. either x or y will do. What I have done is to enclose the original query like this SELECT * FROM (<original query text>) Results group by QID,AID Is there a better way to go about this? The original query uses multiple joins and unions and what not, So I would prefer not to touch it unless its absolutely necesary

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  • Getting records from a table based on a filter field and Between but also having the OR login for mu

    - by Pentium10
    I have a this table, where I store multiple ids and an age range (def1,def2) CREATE TABLE "template_requirements" ("_id" INTEGER NOT NULL, "templateid" INTEGER, "def1" VARCHAR(255), "def2" VARCHAR(255), PRIMARY KEY("_id")) Having values such as: templateid | def1 | def2 100 | 7 | 25 200 | 40 | 90 300 | 7 | 25 300 | 40 | 60 as you see for templateid 300 we have an or logic: age between 7 and 25 or age between 40 and 60. I want to get all the template ids that are not for a certain age like 25... What's the problem? If I run a query like this one: SELECT group_concat(templateid) FROM template_requirements where and '25' not between cast(def1 as integer) and cast(def2 as integer) it returns 200, 300, which is wrong, as the 300 matched on row 40 to 60, but shouldn't be included in the result as we have a condition with same templateid 7 to 25 that fails the not beetween stuff. How would be the correct query in SQLite, I would like to keep the group_concat stuff.

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  • Database design

    - by Hadad
    Hello, I've a system, that have two types of users (Companies and individuals).all types have a shared set of properties but they differ in another. What is the best design merge all in one table that allows null for unmatched properties, or separate them in two tables related to a basic table with a one to one relationship. Thanks.

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  • Does UNIQ constraint mean also an index on that field(s)?

    - by Gremo
    As title, should i defined a separate index on email column (for searching purposes) or the index is "automatically" added along with UNIQ_EMAIL_USER constraint? CREATE TABLE IF NOT EXISTS `customer` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_id` int(11) NOT NULL, `first` varchar(255) NOT NULL, `last` varchar(255) NOT NULL, `slug` varchar(255) NOT NULL, `email` varchar(255) NOT NULL, `created_at` datetime NOT NULL, `updated_at` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `UNIQ_SLUG` (`slug`), UNIQUE KEY `UNIQ_EMAIL_USER` (`email`,`user_id`), KEY `IDX_USER` (`user_id`) ) ENGINE=InnoDB;

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  • Create a trigger that updates a column on one table when a column in another table is updated

    - by GigaPr
    Hi, i have two tables Order(id, date, note) and Delivery(Id, Note, Date) I want to create a trigger that updates the date in Delivery when the date is updated in Order. I was thinking to do something like CREATE OR REPLACE TRIGGER your_trigger_name BEFORE UPDATE ON Order DECLARE BEGIN UPDATE Delivery set date = ??? where id = ??? END; How do I get the date and row id? thanks

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  • copy an identity column into another table

    - by slake
    I have 2 tables that are related,both have identity columns for primary keys and i am using a vb form to insert data into them,My problem is that i cannot get the child table to get the primary key of the parent table and use this as its foreign key in my database. the data is inserted fine though no foreign key constraint is made.I am wondering if a trigger will do it and if so how. All my inserting of data is done in vb. The user wont insert any keys. all these are identity columns that are auto generated. If a trigger is my way out please illustrate with an example. If there is another way i can do this in VB itself then please advise and an example will be greatly appreciated Thanks in advance

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  • what is the 'extra' mean in this django code..

    - by zjm1126
    TOPIC_COUNT_SQL = """ SELECT COUNT(*) FROM topics_topic WHERE topics_topic.object_id = maps_map.id AND topics_topic.content_type_id = %s """ MEMBER_COUNT_SQL = """ SELECT COUNT(*) FROM maps_map_members WHERE maps_map_members.map_id = maps_map.id """ maps = maps.extra(select=SortedDict([ ('member_count', MEMBER_COUNT_SQL), ('topic_count', TOPIC_COUNT_SQL), ]), select_params=(content_type.id,)) i don't know this mean, thanks

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