inner-join

问题 I have a scenario which I'm a bit stuck on. Let's say I have a survey about colors, and I have one table for the color data, and another for people's answers. tbColors color_code , color_name 1 , 'blue' 2 , 'green' 3 , 'yellow' 4 , 'red' tbAnswers answer_id , favorite_color , least_favorite_color , color_im_allergic_to 1 , 1 , 2 3 2 , 3 , 1 4 3 , 1 , 1 2 4 , 2 , 3 4 For display I want to write a SELECT that presents the answers table but using the color_name column from tbColors. I understand

问题 I have this database query SELECT * FROM (`metadata` im) INNER JOIN `content` ic ON `im`.`rev_id` = `ic`.`rev_id` WHERE `im`.`id` = '00039' AND `current_revision` = 1 ORDER BY `timestamp` DESC LIMIT 5, 5 The query limits the total rows in the result to 5. I want to limit the left table metadata to 5 without limiting the entire result-set. How should I write the query? 回答1: If you think about what you are trying to do, you're not really doing a select against metadata . You need to sub query

问题 I have 2 tables like below location_distance ---------------------------------------------- id | fromLocid | toLocid | distance ---------------------------------------------- 1 | 3 | 5 | 70 2 | 6 | 8 | 15 3 | 2 | 4 | 63 ... other_table -------------------------------------------- Id | fromLocid | toLocid | otherdata -------------------------------------------- 12 | 5 | 3 | xxxx 22 | 2 | 4 | xxxx 56 | 8 | 6 | xxxx 78 | 3 | 5 | xxxx I would like to retrieve the distance b/w the locations in

问题 I have this question, from I am trying to get through. I have been trying to do this for hours, it would be really great if someone could point us in the right direction. This is in german so I am going to translate it in English: We only have problem with part (d) (d) Write an SQL statement that gives names of the restaurant and Ort(Place) of the restaurant that do not order any Salat. The expected result would be: Da Mafia : Göttingen Venezia : Kassel 回答1: You can try like this: SELECT name

问题 I Had a problem with order by when joins multiple tables which have millions of data. But I got solution as instead of join with distinct use of EXISTS will improve performance from the following question How to improve order by performance with joins in mysql SELECT `tracked_twitter` . *, COUNT( * ) AS twitterContentCount, retweet_count + favourite_count + reply_count AS engagement FROM `tracked_twitter` INNER JOIN `twitter_content` ON `tracked_twitter`.`id` = `twitter_content`.`tracked

问题 Let's imagine I have an table called Foo with a primary key FooID and an integer non-unique column Bar. For some reason in a SQL query I have to join table Foo with itself multiple times, like this: SELECT * FROM Foo f1 INNER JOIN Foo f2 ON f2.Bar = f1.Bar INNER JOIN Foo f3 ON f3.Bar = f1.Bar... I have to achieve this via LINQ to Entities. Doing ObjectContext.Foos.Join(ObjectContext.Foos, a => a.Bar, b => b.Bar, (a, b) => new {a, b}) gives me LEFT OUTER JOIN in the resulting query and I need

问题 I have two tables named login and userDetail Login login_id uname pswd userdetail_id and userdetails userdetail_id name address email the login table contain userdetails_id in the userDetail table. i want to get all data from Login table and userDetail table and save it to a variable if anyone knows, please answer me...... 回答1: First of all your table structure must be as below. logins Table. Id auto_increment username password userDetails Table. Id auto_increment user_id name address etc...

问题 Some quick nhibernate problem: I have sql tables: Item { Id, Name } ItemRange { Id, Name } ItemHasItemRange { Id, ItemId, ItemRangeId } Mappings are simple, so I will not paste them, the ItemId and ItemRangeId are foreign keys, Item class has ItemHasItemRanges collection mapped as lazy bag. I want all items which are in particular ItemRange, but I do not want to retrieve associated ItemRangeObjects, I just want to do inner join to narrow results. When I do it like that: c.CreateCriteria("Item

问题 Have some data that looks like this: widget: { categories: ['hair', 'nails', 'dress'] colors: ['red', 'white'] } The data needs to be queried like this: SELECT * FROM widget_table WHERE categories == 'hair' AND colors == 'red' Would like to put this data into a MongoDB sharded cluster. However, it seems like an ideal shard key would not be a list field. In this case, that is not possible because all of the fields are list fields. Is it possible to use a list field, such as the field

问题 I am doing a query to return all users shopping carts, stored in the sb_carts table. The product information stored in sb_carts is referenced over two keys product_sku and school_id. It needs to reference both to return a unique product with unique stock levels etc. When I execute the following query it returns one row, I am expecting 3 rows. I have tried breaking the inner join into two separate joins but this still returns only 1 result. joining only on one key has the desired result, but