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• Query - Trying to SUM one field based on content of another field

  - by ShaneL

  Table: DayOfWeek Enrollments Monday 35 Monday 12 Saturday 25 Tuesday 15 Monday 9 Tuesday 15 Basically I'm trying to sum the total enrolments for each day. so the Output will look like: DayOfWeek Enrollments Monday 56 Saturday 25 Tuesday 30 I've spent around 4 hours trying to work this out trying many many different ways but no luck. The problem I'm having is i can count how many enrollments for each day but can't have it aligned with the correct day when i run the query e.g. I want The total to be on the same line as the day it was calculated from. (I hope that is clear enough)

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• CASE + IF MysQL query

  - by terence6

  Problem is as follows. I have a product that can be in one of three categories (defined by category_id). Each category table has category_id field related to category_id in product table. So I have 3 cases. I'm checking If my product.category_id is in table one. If yes, I take some values. If not I check in tables that are left. What can I write In the ELSE section? Can anyone correct my query ? CASE WHEN IF EXISTS(SELECT * FROM table1 WHERE category_id='category_id') THEN SELECT type_id FROM table1 WHERE category_id='category_id'; WHEN IF EXISTS(SELECT * FROM table2 WHERE category_id='category_id') THEN SELECT value_id FROM table2 WHERE category_id='category_id'; WHEN IF EXISTS(SELECT * FROM table3 WHERE category_id='category_id') THEN SELECT group_id FROM table3 WHERE category_id='category_id'; ELSE "dont know what here"; END;

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• Help constructing query - Compare columns and replace numbers

  - by Tommy

  I have a feeling that this query is pretty easy to construct, I just can't figure it out. I want to replace all numbers in table X column C, with numbers in table Z column A, where numbers from table X column C matches numbers in table Z column B. I hope that makes sense. Perhaps a little background information will make it clearer. I've converted from one CMS to another, and the module I used to convert mapped the ids to the new database. Table X column A is the new id's. Table X column B is the old id's. Table Z is the table for an image gallery that I migrated, and column C contains the id's of the images owners. Can anyone crack this nut?

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• SQL query help - merge a value to all rows in a column

  - by Tommy

  I'm trying to migrate a site from a joomla system to a drupal. The problem is that drupal needs filename and sourcepath in the same row, but joomla only has filename. I'm looking for a way to add sourcepath before the filename in all the rows in that column. I'm figuring it's the UPDATE statement that I should use, but I can't figure out how to construct the query. There's a person with a similar problem here, but I don't find the answers in that thread helpful to my problem: http://www.daniweb.com/forums/showth...t+value&page=2 Any suggestions?

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• Sql-server Database query help

  - by menacheb

  Hi, I have a problem that I didn't manage to solve for a very long time, and I quite desperate. I have a Database (SQL Server) with table named 'ProcessData' and columns named 'Process_Name' (Data Type: nvarchar(50)), 'Start_At' (DataType: DateTime) and 'End_At' (Data Type: DateTime). I need to know for each 'Time-Interval' (let's say 1 minute) how many processes (Process_Name = PN) was open (after or equal to the 'Start_at' column and before or equal to the 'End_At' column) during this time (It can be a few rows with the same data). Does anyone know how to make this query without a 'for' loop? (It ITSELF will promote the time), (The answer will be a table with two columns (1. The time the check took place. 2. the number of open processes at this time.) and a row for each 'Time-Interval' (1 minute in this example ) Many thanks,

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• MySQL query problem

  - by SaltLake

  I've got MySQL table CREATE TABLE stat ( ID int NOT NULL auto_increment PRIMARY KEY, TIMESTAMP_X timestamp DEFAULT CURRENT_TIMESTAMP, # ... some other fields ... ) which contains statistics about site visitors. For getting visits per hour I use SELECT hour(TIMESTAMP_X) as HOUR , count(*) AS HOUR_STAT FROM cms_webstat GROUP BY HOUR ORDER BY HOUR DESC which gives me | HOUR | HOUR_STAT | | 24 | 15 | | 23 | 12 | | 22 | 9 | | 20 | 3 | | 18 | 2 | | 15 | 1 | | 12 | 3 | | 9 | 1 | | 3 | 5 | | 2 | 7 | | 1 | 9 | | 0 | 12 | And I'd like to get following: | HOUR | HOUR_STAT | | 24 | 15 | | 23 | 12 | | 22 | 9 | | 21 | 0 | | 20 | 3 | | 19 | 0 | | 18 | 2 | | 17 | 0 | | 16 | 0 | | 15 | 1 | | 14 | 0 | | 13 | 0 | | 12 | 3 | | 11 | 0 | | 10 | 0 | | 9 | 1 | | 8 | 0 | | 7 | 0 | | 6 | 0 | | 5 | 0 | | 4 | 0 | | 3 | 5 | | 2 | 7 | | 1 | 9 | | 0 | 12 | How should I modify the query to get such result? Thanks.

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• Need help with some complex SQL query

  - by Psyche

  Hello guys, I need some help with a complex SQL query. Here's my setup: there are two tables, one with authors, and another with books. The books table contains a field named "author" which holds author's id. If a book has more than one author, then the "author" field will contain all the authors ids separated by ";" (something like 2;34;234). On the website I have to list all the books written by an author. If there's only one author, its simple, but how can I get those books where the author I'm interested in is the second or third author? Many thanks.

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• sql query is too slow, how to improve speed

  - by user1289282

  I have run into a bottleneck when trying to update one of my tables. The player table has, among other things, id, skill, school, weight. What I am trying to do is: SELECT id, skill FROM player WHERE player.school = (current school of 4500) AND player.weight = (current weight of 14) to find the highest skill of all players returned from the query UPDATE player SET starter = 'TRUE' WHERE id = (highest skill) move to next weight and repeat when all weights have been completed move to next school and start over all schools completed, done I have this code implemented and it works, but I have approximately 4500 schools totaling 172000 players and the way I have it now, it would take probably a half hour or more to complete (did not wait it out), which is way too slow. How to speed this up? Short of reducing the scale of the system, I am willing to do anything that gets the intended result. Thanks! *the weights are the standard folk style wrestling weights ie, 103, 113, 120, 126, 132, 138, 145, 152, 160, 170, 182, 195, 220, 285 pounds

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• Django query - join on the same table

  - by dana

  i have a mini blog app, and a 'timeline' . there i want to be displayed all the posts from all the friends of a user, plus the posts of that user himself. For that, i have to make some kind of a 'join' between the results of two queries (queries on the same table) , so that the final result will be the combination of the user - posesor of the account, and all his friends. My query looks like this: blog = New.objects.filter(created_by = following,created_by = request.user) By that ',' i wanted to make a 'join' -i found something like this on a doc- but this method is not correct- i'm getting an error. How else could be done this 'join' ? Thanks!

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• Counting multiple rows in MySQL in one query

  - by diggersworld

  I currently have a table which stores a load of statistics such as views, downloads, purchases etc. for a multiple number of items. To get a single operation count on each item I can use the following query: SELECT , COUNT() FROM stats WHERE operation = 'view' GROUP BY item_id This gives me all the items and a count of their views. I can then change 'view' to 'purchase' or 'download' for the other variables. However this means three separate calls to the database. Is it possible to get all three in one go?

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• Update query (access & vb.net)

  - by yae

  Hi: I have to update some fields of a table of access according to the value of parameter. If this paramter is "true" I need to update. Table idInvoice price percentageTax1 tax1 percentageTax2 tax2 total Example values: idinvoice: 12300 price: 100 € percentageTax1: 10 % tax1= 10€ percentageTax2: 5 % tax2: 5€ total: 115 € (result: 100€+10€+5€) Ok. If the parameter on that I have commented before is "true" I must update the percentages and then update the total. I need to replace the "old" percentages by new percent. Ok I can do it in 3 queries: update invocies set percentageTax1=20,tax1=price *(percentageTax1/100) where idInvoice=@number and percentageTax1=10 update invocies set percentageTax2=7,tax2=price *(percentageTax2/100) where idInvoice=@number and percentageTax2=5 update invocies set total=price+tax1+tax2 where idInvoice=@number . But my question is: is there any an alternative to do this in 1 query?

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• [SQL][MS access] Query to find duplicate item in 2 table

  - by Rico

  I have this table Antecedent Consequent I1 I2 I1 I1,I2,I3 I1 I4,I1,I3,I4 I1,I2 I1 I1,I2 I1,I4 I1,I2 I1,I3 I1,I4 I3,I2 I1,I2,I3 I1,I4 I1,I3,I4 I4 AS you can see it's pretty messed up. is there anyway i can remove rows if item in consequent exist in antecedent (in 1 row) for example: INPUT: Antecedent Consequent I1 I2 I1 I1,I2,I3 <---- DELETE since I1 exist in antecedent I1 I4,I1,I3,I4 <---- DELETE since I1 exist in antecedent I1,I2 I1 <---- DELETE since I1 exist in antecedent I1,I2 I1,I4 <---- DELETE since I1 exist in antecedent I1,I2 I1,I3 <---- DELETE since I1 exist in antecedent I1,I4 I3,I2 <---- DELETE since I2 exist in antecedent I1,I2,I3 I1,I4 I1,I3,I4 I4 <---- DELETE since I4 exist in antecedent OUTPUT: Antecedent Consequent I1 I2 I1,I2,I3 I1,I4 is there anyway i can do that by query?

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• SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best

  - by pinaldave

  This is followup post of my earlier article SQL SERVER – Convert IN to EXISTS – Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly same resultset. USE AdventureWorks GO -- use of = SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of in SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of exists SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- Use of Join SELECT * FROM HumanResources.Employee E INNER JOIN HumanResources.EmployeeAddress EA ON E.EmployeeID = EA.EmployeeID GO Let us compare the execution plan of the queries listed above. Click on image to see larger image. It is quite clear from the execution plan that in case of IN, EXISTS and JOIN SQL Server Engines is smart enough to figure out what is the best optimal plan of Merge Join for the same query and execute the same. However, in the case of use of Equal (=) Operator, SQL Server is forced to use Nested Loop and test each result of the inner query and compare to outer query, leading to cut the performance. Please note that here I no mean suggesting that Nested Loop is bad or Merge Join is better. This can very well vary on your machine and amount of resources available on your computer. When I see Equal (=) operator used in query like above, I usually recommend to see if user can use IN or EXISTS or JOIN. As I said, this can very much vary on different system. What is your take in above query? I believe SQL Server Engines is usually pretty smart to figure out what is ideal execution plan and use it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Subquery or Join – Various Options – SQL Server Engine Knows the Best – Part 2

  - by pinaldave

  This blog post is part 2 of the earlier written article SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best by Paulo R. Pereira. Paulo has left excellent comment to earlier article once again proving the point that SQL Server Engine is smart enough to figure out the best plan itself and uses the same for the query. Let us go over his comment as he has posted. “I think IN or EXISTS is the best choice, because there is a little difference between ‘Merge Join’ of query with JOIN (Inner Join) and the others options (Left Semi Join), and JOIN can give more results than IN or EXISTS if the relationship is 1:0..N and not 1:0..1. And if I try use NOT IN and NOT EXISTS the query plan is different from LEFT JOIN too (Left Anti Semi Join vs. Left Outer Join + Filter). So, I found a case where EXISTS has a different query plan than IN or ANY/SOME:” USE AdventureWorks GO -- use of SOME SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = SOME ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of IN SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of EXISTS SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) When looked into execution plan of the queries listed above indeed we do get different plans for queries and SQL Server Engines creates the best (least cost) plan for each query. Click on image to see larger images. Thanks Paulo for your wonderful contribution. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Contribution, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Modify Wordpress SQL Query to pull from within a category

  - by Levi

  Hi I am using a wordpress plugin called "kf most read" which stores a count of how many times a post was read, and lets you output a list of most read posts. This works well. The issue is, I am trying to pull the most read posts, but only the most read posts within the current category you are viewing. I am close to clueless when it comes to sql. Here us what the plugin is currently using to pull the most read posts: $sql = "SELECT count(mr.post_ID) as totHits, p.ID, p.post_title from $wpdb-posts p JOIN {$wpdb-prefix}kf_most_read mr on mr.post_ID = p.ID where mr.hit_ts = '".(time() - ( 86400 * $period))."' GROUP BY mr.post_ID order by totHits desc, ID ASC LIMIT $limit"; How could I incorporate the below query which pulls from a specific category into the above? $sql .= "LEFT JOIN $wpdb-term_taxonomy ON($wpdb-term_relationships.term_taxonomy_id = $wpdb-term_taxonomy.term_taxonomy_id)" ; $sql .= "WHERE $wpdb-term_taxonomy.term_id IN ($currentcat)" ; $sql .= "AND $wpdb-term_taxonomy.taxonomy = 'category'" ; Any Help on this would be much appreciated.

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• Help Converting T-SQL Query to LINQ Query

  - by campbelt

  I am new to LINQ, and so am struggle over some queries that I'm sure are pretty simple. In any case, I have been hiting my head against this for a while, but I'm stumped. Can anyone here help me convert this T-SQL query into a LINQ query? Once I see how it is done, I'm sure I'll have some question about the syntax: SELECT BlogTitle FROM Blogs b JOIN BlogComments bc ON b.BlogID = bc.BlogID WHERE b.Deleted = 0 AND b.Draft = 0 AND b.[Default] = 0 AND bc.Deleted = 0 GROUP BY BlogTitle ORDER BY MAX([bc].[Timestamp]) DESC Just to show that I have tried to solve this on my own, here is what I've come up with so far, though it doesn't compile, let alone work ... var iqueryable = from blog in db.Blogs join blogComment in db.BlogComments on blog.BlogID equals blogComment.BlogID where blog.Deleted == false && blog.Draft == false && blog.Default == false && blogComment.Deleted == false group blogComment by blog.BlogID into blogGroup orderby blogGroup.Max(blogComment => blogComment.Timestamp) select blogGroup;

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• sql pulling a row for next or previous row of a current row

  - by basit.

  id | photo title | created_date XEi43 | my family | 2009 08 04 dDls | friends group | 2009 08 05 32kJ | beautiful place | 2009 08 06 EOIk | working late | 2009 08 07 Say I have the id 32kJ. How would I get the new or previous row?

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• Slow MySQL Query Breaking my back!

  - by Chris n

  so, I have tried everything I can think of, and can't get this query to happen in less than 3 seconds on my local server. I know the problem has to do with the OR referencing both the owner_id and the person_id. if I run one or the other it happens instantly, but together with an or I can't seem to make it work - I looked into rewriting the code, but the way the app was designed it won't be easy. is there a way I can call an equivalent or that won't take so long? here is the sql: SELECT event_types.name as event_type_name,event_types.id as id, count(events.id) as count,sum(events.estimated_duration) as time_sum FROM events,event_types WHERE event_types.id = events.event_type_id AND events.event_type_id != '4' AND ( events.status!='cancelled') AND events.event_type_id != 64 AND ( events.owner_id = 161 OR events.person_id = 161 ) GROUP BY event_types.name ORDER BY event_types.name DESC; Here's the Explain soup, although I'm guessing it's unnecessary cause there is probably a better way to structure that or that is obvious: thanks so much! chris. +----+-------------+-------------+-------+---------------------------------------------------------------------------------------------------------+-------------------------------+---------+-------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------+-------+---------------------------------------------------------------------------------------------------------+-------------------------------+-- | 1 | SIMPLE | event_types | range | PRIMARY | PRIMARY | 4 | NULL | 78 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | events | ref | index_events_on_status,index_events_on_event_type_id,index_events_on_person_id,index_events_on_owner_id | index_events_on_event_type_id | 5 | thenumber_production.event_types.id | 907 | Using where | +----+-------------+-------------+-------+---------------------------------------------------------------------------------------------------------+-------------------------------+---------+-------------------------------------+------+----------------------------------------------+

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• Help with MySQL query - Product orders report without duplicate shipping charges

  - by Paul

  Hello, I have an issue creating a custom report for an e-commerce store running on osCommerce. The client wants the report to have the following columns: Date, Order ID, Product Class, Product Price, Product Tax, Shipping, Order Total The criteria for generating the report are Date Range and Product Class (Textbooks for example) The client wants the report to list each Textbook purchased on its own line. Orders with multiple textbooks would display a separate line for each Textbook in the order. I have it all working except for one part: the shipping amount is order-specific (based on the order total), not product-specific, and is displaying for each product. I need it to display only for the first product of each order, so it is not counted more than once. My current query is: SELECT op.date_funds_captured as 'Date', op.orders_id as 'Order ID', pc.class as 'Product Class', round(op.products_price,2) as 'Product Price', round(op.products_tax*op.products_price/100,2) as 'Product Tax', round(otship.value,2) as 'Shipping', round(ot.value,2) as 'Order Total' from orders_products op, orders_total ot, orders_total otship, productclasses pc, products p where ot.orders_id = op.orders_id and ot.class='ot_total' and op.orders_id = otship.orders_id and otship.class = 'ot_shipping' and p.products_class_id = pc.id and op.products_id = p.products_id and pc.id = 1 pc.id = 1 -- Product class = Textbook Here is an example of the current report output. You can see the problem with order 2256 showing the shipping value three times instead of once: Date Order Product Class Price Tax Shipping Total 2010-01-04 2253 Textbook 24.95 2.43 10.03 37.41 2010-01-04 2256 Textbook 34.95 0.00 18.09 240.37 2010-01-04 2256 Textbook 55.50 0.00 18.09 240.37 2010-01-04 2256 Textbook 36.95 0.00 18.09 240.37 2010-01-04 2258 Textbook 55.50 5.41 12.17 124.24 Please help!!! Thanks, Paul

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• Command-Query-Separation and multithreading safe interfaces

  - by Tobias Langner

  I like the command query separation pattern (from OOSC / Eiffel - basically you either return a value or you change the state of the class - but not both). This makes reasoning about the class easier and it is easier to write exception safe classes. Now, with multi threading, I run into a major problem: the separation of the query and the command basically invalidates the result from the query as anything can happen between those 2. So my question is: how do you handle command query separation in an multi-threaded environment? Clarification example: A stack with command query separation would have the following methods: push (command) pop (command - but does not return a value) top (query - returns the value) empty (query) The problem here is - I can get empty as status, but then I can not rely on top really retrieving an element since between the call of empty and the call of top, the stack might have been emptied. Same goes for pop & top. If I get an item using top, I can not be sure that the item that I pop is the same. This can be solved using external locks - but that's not exactly what I call threadsafe design.

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• How to query collections in NHibernate

  - by user305813

  Hi, I have a class: public class User { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IDictionary<string, string> Attributes { get; set; } } and a mapping file: <class name="User" table="Users"> <id name="Id"> <generator class="hilo"/> </id> <property name="Name"/> <map name="Attributes" table="UserAttributes"> <key column="UserId"/> <index column="AttributeName" type="System.String"/> <element column="Attributevalue" type="System.String"/> </map> </class> So now I can add many attributes and values to a User. How can I query those attributes so I can get ie. Get all the users where attributename is "Age" and attribute value is "20" ? I don't want to do this in foreach because I may have millions of users each having its unique attributes. Please help

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• conditional update records mysql query

  - by Shakti Singh

  Hi, Is there any single msql query which can update customer DOB? I want to update the DOB of those customers which have DOB greater than current date. example:- if a customer have dob 2034 update it to 1934 , if have 2068 updated with 1968. There was a bug in my system if you enter date less than 1970 it was storing it as 2070. The bug is solved now but what about the customers which have wrong DOB. So I have to update their DOB. All customers are stored in customer_entity table and the entity_id is the customer_id Details is as follows:- desc customer_entity -> ; +------------------+----------------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+----------------------+------+-----+---------------------+----------------+ | entity_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | entity_type_id | smallint(8) unsigned | NO | MUL | 0 | | | attribute_set_id | smallint(5) unsigned | NO | | 0 | | | website_id | smallint(5) unsigned | YES | MUL | NULL | | | email | varchar(255) | NO | MUL | | | | group_id | smallint(3) unsigned | NO | | 0 | | | increment_id | varchar(50) | NO | | | | | store_id | smallint(5) unsigned | YES | MUL | 0 | | | created_at | datetime | NO | | 0000-00-00 00:00:00 | | | updated_at | datetime | NO | | 0000-00-00 00:00:00 | | | is_active | tinyint(1) unsigned | NO | | 1 | | +------------------+----------------------+------+-----+---------------------+----------------+ 11 rows in set (0.00 sec) And the DOB is stored in the customer_entity_datetime table the column value contain the DOB. but in this table values of all other attribute are also stored such as fname,lname etc. So the attribute_id with value 11 is DOB attribute. mysql> desc customer_entity_datetime; +----------------+----------------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------------+----------------------+------+-----+---------------------+----------------+ | value_id | int(11) | NO | PRI | NULL | auto_increment | | entity_type_id | smallint(8) unsigned | NO | MUL | 0 | | | attribute_id | smallint(5) unsigned | NO | MUL | 0 | | | entity_id | int(10) unsigned | NO | MUL | 0 | | | value | datetime | NO | | 0000-00-00 00:00:00 | | +----------------+----------------------+------+-----+---------------------+----------------+ 5 rows in set (0.01 sec) Thanks.

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• Query Access and VB.NET

  - by yae

  Hi all: I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are vinculated with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5));

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• Can't return a List from a Compiled Query.

  - by Andrew

  I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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• Help Me With This Access Query

  - by yae

  I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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