greatest-n-per-group

问题 I am trying to select of the duplicate rows in mysql table it's working fine for me but the problem is that it is not letting me select all the fields in that query , just letting me select the field name i used as distinct , lemme write the query for better understading mysql_query("SELECT DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id") mysql_query("SELECT * , DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id") 1st one is working fine now when i am trying to select all fields

问题 I have two SQLite tables like this: AuthorId | AuthorName ---------------------- 1 | Alice 2 | Bob 3 | Carol ... | .... BookId | AuthorId | Title ---------------------------------- 1 | 1 | aaa1 2 | 1 | aaa2 3 | 1 | aaa3 4 | 2 | ddd1 5 | 2 | ddd2 ... | ... | ... 19 | 3 | fff1 20 | 3 | fff2 21 | 3 | fff3 22 | 3 | fff4 I want to make a SELECT query that will return the first N (e.g. two) rows for each AuthorId, ordering by Title ("Select the first two books of each author"). Sample output:

问题 I am storing the response to various rpc calls in a mysql table with the following fields: Table: rpc_responses timestamp (date) method (varchar) id (varchar) response (mediumtext) PRIMARY KEY(timestamp,method,id) What is the best method of selecting the most recent responses for all existing combinations of method and id ? For each date there can only be one response for a given method/id. Not all call combinations are necessarily present for a given date. There are dozens of methods,

问题 I am storing the response to various rpc calls in a mysql table with the following fields: Table: rpc_responses timestamp (date) method (varchar) id (varchar) response (mediumtext) PRIMARY KEY(timestamp,method,id) What is the best method of selecting the most recent responses for all existing combinations of method and id ? For each date there can only be one response for a given method/id. Not all call combinations are necessarily present for a given date. There are dozens of methods,

问题 I am storing the response to various rpc calls in a mysql table with the following fields: Table: rpc_responses timestamp (date) method (varchar) id (varchar) response (mediumtext) PRIMARY KEY(timestamp,method,id) What is the best method of selecting the most recent responses for all existing combinations of method and id ? For each date there can only be one response for a given method/id. Not all call combinations are necessarily present for a given date. There are dozens of methods,

问题 I have a table that has the following columns Id ForeignKeyId AttributeName AttributeValue Created Some of the data may look like this: 1, 1, 'EmailPreference', 'Text', 1/1/2010 2, 1, 'EmailPreference', 'Html', 1/3/2010 3, 1, 'EmailPreference', 'Text', 1/10/2010 4, 2, 'EmailPreference', 'Text', 1/2/2010 5, 2, 'EmailPreference', 'Html', 1/8/2010 I'd like to run a query that pulls the most recent value of the AttributeValue column for each distinct ForeignKeyId andAttributeName, using the

问题 I have a table that has the following columns Id ForeignKeyId AttributeName AttributeValue Created Some of the data may look like this: 1, 1, 'EmailPreference', 'Text', 1/1/2010 2, 1, 'EmailPreference', 'Html', 1/3/2010 3, 1, 'EmailPreference', 'Text', 1/10/2010 4, 2, 'EmailPreference', 'Text', 1/2/2010 5, 2, 'EmailPreference', 'Html', 1/8/2010 I'd like to run a query that pulls the most recent value of the AttributeValue column for each distinct ForeignKeyId andAttributeName, using the

问题 SITUATION I am working on a travel engine site and am writing a complex query to match visitors' search queries with their bookings based on IP Address , Destination and Date so I can work out the conversion ratio later. PROBLEM There needs to be multiple conversion ratios based on a parameter (In this case, the utm_source which I extract from a RequestUrl stored in the searches table). The problem is some users make multiple searches from different locations.. sometimes we get the utm_source

问题 I have some problem with my SQL query I have table message and table recipient message is ID author date -------------------- 0 1 2013-07-08 05:38:47 1 1 2013-07-13 05:38:47 2 1 2013-07-15 05:38:47 3 1 2013-07-15 05:38:47 4 2 2013-07-17 05:38:47 5 1 2013-07-28 05:38:47 recipient is ID m_id recipient -------------------- 0 0 2 1 1 2 2 2 3 3 3 2 4 4 1 5 5 2 I need return rows from table message with group by recipient column from table recipient with last date in message table I'll try this

问题 I have these two tables: popular_song song_name | rate | country_id ------------------------------ Tic Tac | 10 | 1 Titanic | 2 | 1 Love Boat | 8 | 2 Battery | 9 | 2 country conutry_id | country -------------------------- 1 | United States 2 | Germany What I'd like to achieve is to get the most poular song in each country, e.g.: song_name | rate | country -------------------------- Tic Tac | 10 | United States Battery | 9 | Germany I've tried this query: SELECT MAX(rate), song_name, country