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  • Has anyone ever successfully make index merge work for MySQL?

    - by user198729
    Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing? Update mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 1863 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Version: mysql> select version(); +----------------------+ | version() | +----------------------+ | 5.1.36-community-log | +----------------------+ Has anyone ever successfully make index merge work for MySQL? I'll be glad to see successful stories here:)

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  • How do I get every nth row in a table, or how do I break up a subset of a table into sets or rows of

    - by Jherico
    I have a table of heterogeneous pieces of data identified by a primary key (ID) and a type identifier (TYPE_ID). I would like to be able to perform a query that returns me a set of ranges for a given type broken into even page sizes. For instance, if there are 10,000 records of type '1' and I specify a page size of 1000, I want 10 pairs of numbers back representing values I can use in a BETWEEN clause in subsequent queries to query the DB 1000 records at a time. My initial attempt was something like this select id, rownum from CONTENT_TABLE where type_id = ? and mod(rownum, ?) = 0 But this doesn't work.

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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  • Query crashes MS Access

    - by user284651
    THE TASK: I am in the process of migrating a DB from MS Access to Maximizer. In order to do this I must take 64 tables in MS ACCESS and merge them into one. The output must be in the form of a TAB or CSV file. Which will then be imported into Maximizer. THE PROBLEM: Access is unable to perform a query that is so complex it seems, as it crashes any time I run the query. ALTERNATIVES: I have thought about a few alternatives, and would like to do the least time-consuming one, out of these, while also taking advantage of any opportunities to learn something new. Export each table into CSVs and import into SQLight and then make a query with it to do the same as what ACCESS fails to do (merge 64 tables). Export each table into CSVs and write a script to access each one and merge the CSVs into a single CSV. Somehow connect to the MS ACCESS DB (API), and write a script to pull data from each table and merge them into a CSV file. QUESTION: What do you recommend?

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  • sequence of events in ACCESS

    - by I__
    what is the proper way of doing the following: getting DATE as user input running a query generating a report that uses the query this is the solution i was thinking: have a form that takes user input run the query open the report what is the correct way of doing this?

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  • Multiple user database design

    - by dieguitoweb
    I have to develop a basic social network for an academic purpose; but I need some tips for the users management.. The users are subdivided into 3 groups with different privilege: admins,analysts and standards users. For every user should be stored into the database the following information: name,lastname,e-mail,age,password. I'm not quite sure how I should design the database between theese two solutions: 1)one table called 'users' with the 'role' attribute that explain what a user can do and what can't do, and the permissions are managed via php 2)every application user is a database user created with the query 'CREATE ROLE' (It's a postgres database) and he has permissions on some tables granted with the 'GRANT' statement You should take into account that the project is for a database exam.. thanks

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  • SimpleDB as Denormalized DB

    - by Max
    In an environment where you have a relational database which handles all business transactions is it a good idea to utilise SimpleDB for all data queries to have faster and more lightweight search? So the master data storage would be a relational DB which is "replicated"/"transformed" into SimpleDB to provide very fast read only queries since no JOINS and complicated subselects are needed.

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  • What's the best way to access a MS Access database using PHP?

    - by Jack Roscoe
    Hi, I need to access some data from an MS Access database and retrieve some data from it using PHP. I've looked around the web, and found the following line which seems to correctly connect to the database: $conn->Open("DRIVER={Microsoft Access Driver (*.mdb)}; DBQ=C:\wamp\www\data\MYDB.mdb"); However, I have tried to retrieve some data in the following way: $query = "SELECT pageid FROM pages_table"; $result = mysqli_query($conn, $query); $amount_of_pages = 0; if(mysqli_num_rows($result) <= 0) echo "No results found."; else while($row = mysqli_fetch_array($result, MYSQL_ASSOC)) $amount_of_pages++; And was presented with the following errors: Warning: mysqli_query() expects parameter 1 to be mysqli, object given in C:\wamp\www\data\index.php on line 19 Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in C:\wamp\www\data\index.php on line 23 No results found. I don't really understand the connection to the Access database, is there something I should be doing differently? Thanks in advance for any help.

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  • 2-column table with two foreign keys. Performance/design question.

    - by Emanuel
    Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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  • Relation to multiple tables of different types for rating?

    - by Tronic
    i have a table structure like this Products Team Images and want to implement a rating/commenting-feature, where users can rate each entry of all tables. what's the best way to make a single rating table? e.g. a user votes a a product and a team entry, and it should be possible to get alle these entries from a single table. what kind of table-structure is best for this purpose? i hope, my questions is clear enough :/ thanks in advance!

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  • get n records at a time from a temporary table

    - by Claudiu
    I have a temporary table with about 1 million entries. The temporary table stores the result of a larger query. I want to process these records 1000 at a time, for example. What's the best way to set up queries such that I get the first 1000 rows, then the next 1000, etc.? They are not inherently ordered, but the temporary table just has one column with an ID, so I can order it if necessary. I was thinking of creating an extra column with the temporary table to number all the rows, something like: CREATE TEMP TABLE tmptmp AS SELECT ##autonumber somehow##, id FROM .... --complicated query then I can do: SELECT * FROM tmptmp WHERE autonumber>=0 AND autonumber < 1000 etc... how would I actually accomplish this? Or is there a better way? I'm using Python and PostgreSQL.

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  • move data from one table to another, postgresql edition

    - by IggShaman
    Hi All, I'd like to move some data from one table to another (with a possibly different schema). Straightforward solution that comes into mind is - start a transaction with serializable isolation level; INSERT INTO dest_table SELECT data FROM orig_table,other-tables WHERE <condition>; DELETE FROM orig_table USING other-tables WHERE <condition>; COMMIT; Now what if the amount of data is rather big, and the <condition> is expensive to compute? In PostgreSQL, a RULE or a stored procedure can be used to delete data on the fly, evaluating condition only once. Which solution is better? Are there other options?

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  • my output parameters are always null when i use BeginExecuteNonQuery

    - by CharlesO
    I have a stored procedure that returns a varchar(160) as an output parameter of a stored procedure. Everything works fine when i use ExecuteNonQuery, i always get back the expected value. However, once i switch to use BeginExecuteNonQuery, i get a null value for the output. I am using connString + "Asynchronous Processing=true;" in both cases. Sadly the BeginExecuteNonQuery is about 1.5 times faster in my case...but i really need the output parameter. Thanks!

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  • Best .NET Solution for Frequently Changed Database

    - by sestocker
    I am currently architecting a small CRUD applicaton. Their database is a huge mess and will be changing frequently over the course of the next 6 months to a year. What would you recommend for my data layer: 1) ORM (if so, which one?) 2) Linq2Sql 3) Stored Procedures 4) Parametrized Queries I really need a solution that will be dynamic enough (both fast and easy) where I can replace tables and add/delete columns frequently. Note: I do not have much experience with ORM (only a little SubSonic) and generally tend to use stored procedures so maybe that would be the way to go. I would love to learn Ling2Sql or NHibernate if either would allow for the situation I've described above.

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  • Storing Data as XML BLOB

    - by NBrowne
    Hi, At the moment the team i am working with is looking into the possibility of storing data which is entered by users from a series of input wizard screens as an XML blob in the database. the main reason for this being that i would like to write the input wizard as a component which can be brought into a number of systems without having to bring with it a large table structure. To try to clarify if the wizard has 100 input fields (for example) then if i go with the normal relational db structure then their will be a 1 to 1 relationship so will have 100 columns in database. So to get this working in another system will have to bring the tables,strore procedures etc into the new system. I have a number of reservations about this but i would like peoples opinions?? thanks

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  • Getting the last element of a Postgres array, declaratively

    - by Wojciech Kaczmarek
    How to obtain the last element of the array in Postgres? I need to do it declaratively as I want to use it as a ORDER BY criteria. I wouldn't want to create a special PGSQL function for it, the less changes to the database the better in this case. In fact, what I want to do is to sort by the last word of a specific column containing multiple words. Changing the model is not an option here. In other words, I want to push Ruby's sort_by {|x| x.split[-1]} into the database level. I can split a value into array of words with Postgres string_to_array or regexp_split_to_array functions, then how to get its last element?

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  • mysql join 3 tables and count

    - by air
    Please look at this image here is 3 tables , and out i want is uid from table1 industry from table 3 of same uid count of fid from table 2 of same uid like in the sample example output will be 2 records Thanks

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  • Use count or have a field that tallies?

    - by Dan LaManna
    Fairly simple concept, making an extremely basic message board system and I want users to have a post count. Now I was debating on whether or not to have a tally in their row that is added each time a post by them is created, or subtracted by one each time a post of theirs is deleted. However I'm sure that performing a count query when the post count is requested would be more accurate due to unforseen circumstances (say a thread gets deleted and it doesn't lower their tally properly), however this seems like it would be less efficient to run a query EVERY time their post count is loaded, especially in the case of them having 10 posts on the same page and it lists their post count each post. Thoughts/Advice? Thanks

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  • How to get common field in ten tables with different field name

    - by Fero
    Hi all, I am having a common field in ten tables with different field name. example: table1: t1_id     t1_location 1         india 2         china 3         america table2: t2_id     t2_location 4         london 5         australia 6         america Now my o/p should be: location india china america london australia How should i get that using mysql query. thanks in advance

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  • MySQL COUNT() multiple columns

    - by liam
    Hello, I'm trying to fetch the most popular tags from all videos in my database (ignoring blank tags). I also need the 'flv' for each tag. I have this working as I want if each video has one tag: SELECT tag_1, flv, COUNT(tag_1) AS tagcount FROM videos WHERE NOT tag_1='' GROUP BY tag_1 ORDER BY tagcount DESC LIMIT 0, 10 However in my database, each video is allowed three tags - tag_1, tag_2 and tag_3. Is there a way to get the most popular tags reading from multiple columns? The record structure is: +-----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | flv | varchar(150) | YES | | NULL | | | tag_1 | varchar(75) | YES | | NULL | | | tag_2 | varchar(75) | YES | | NULL | | | tag_3 | varchar(75) | YES | | NULL | | +-----------------+--------------+------+-----+---------+----------------+

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  • How to automatically check out a database file in a source controlled web application ?

    - by TheRHCP
    Hello, I am working on an ASP.NET web application, we are a small team (4 students) and we do not have access to a dedicated server to host the database instance. So for this web application we decided just to put the database file in the App_Data folder. The problem is that our project is source controled on TFS, so every time you open the solution and try to launch the web application, we get an expcetion saying that database is read-only. That is logical because the databse file is not automatically checked-out. Is there a workaround to avoid a manual check-out of the database file everytime we open the solution ? Thanks.

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  • Broken count(*) after adding LEFT JOIN

    - by Iain Urquhart
    Since adding the LEFT JOIN to the query below, the count(*) has been returning some strange values, it seems to have added the total rows returned in the query to the 'level': SELECT `n`.*, exp_channel_titles.*, round((`n`.`rgt` - `n`.`lft` - 1) / 2, 0) AS childs, count(*) - 1 + (`n`.`lft` > 1) + 1 AS level, ((min(`p`.`rgt`) - `n`.`rgt` - (`n`.`lft` > 1)) / 2) > 0 AS lower, (((`n`.`lft` - max(`p`.`lft`) > 1))) AS upper FROM `exp_node_tree_6` `n` LEFT JOIN `exp_channel_titles` ON (`n`.`entry_id`=`exp_channel_titles`.`entry_id`), `exp_node_tree_6` `p`, `exp_node_tree_6` WHERE `n`.`lft` BETWEEN `p`.`lft` AND `p`.`rgt` AND ( `p`.`node_id` != `n`.`node_id` OR `n`.`lft` = 1 ) GROUP BY `n`.`node_id` ORDER BY `n`.`lft` I'm totally stumped... Thank you!

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