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I dont know I titled this correct, but let me explain what i am looking for.
I have two tables.
clID (primary key) ClName (varchar)
ID (Primay key) clID (F Key) PlayDate (Date/Time) Score (double)
Client table data looks like this
clID clName 1 Chris 2 Gale 3 Donna
Scores table data looks like this
ID clID PlayDate Score 1 2 23/01/2012 -0.0125 2 2 24/01/2012 0.1011 3 3 24/01/2012 0.0002 4 3 26/01/2012 -0.0056 5 3 27/01/2012 0.0001 6 1 12/01/2012 0.0122 7 1 13/01/2012 0.0053
Is it possible to create a view that will look like this
Date Chris Gale Donna 12/01/2012 0.0122 - - 13/01/2012 0.0053 - - 23/01/2012 - -0.0125 - 24/01/2012 - 0.1011 0.0002 26/01/2012 - - -0.0056 27/01/2012 - - 0.0001
If later there is a another new client then i should be able to check the data for that new client in the new column that will be now created in this view.
Thanks in advance.
This type of data transformation is called a PIVOT. MySQL does not have a pivot function but you can use an aggregate function with a
CASE expression to get the result.
If the names of the
clients is known ahead of time, then you can hard-code the query:
select s.playdate, sum(case when clname = 'Chris' then score end) Chris, sum(case when clname = 'Gale' then score end) Gale, sum(case when clname = 'Donna' then score end) Donna from clients c inner join scores s on c.clid = s.clid group by s.playdate;
See SQL Fiddle with Demo.
If you have an unknown number of clients or you will be adding new clients that you will want included without having to change the code, then you can use a prepared statement to generate dynamic SQL:
SET @sql = NULL; SELECT GROUP_CONCAT(DISTINCT CONCAT( 'sum(CASE WHEN clName = ''', clName, ''' THEN score else ''-'' END) AS `', clName, '`' ) ) INTO @sql FROM clients; SET @sql = CONCAT('SELECT s.playdate, ', @sql, ' from clients c inner join scores s on c.clid = s.clid group by s.playdate'); PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;
See SQL Fiddle with Demo. Both queries will give the same result.
Crosstab View in mySQL?, This type of data transformation is called a PIVOT. MySQL does not have a pivot function but you can use an aggregate function with a CASE� Intelligence that Learns App Patterns & Adapts to Maximize Data Protection.
For a quick 'crosstab' overview of the logins per hour, I use:
SELECT _d , GROUP_CONCAT(LPAD(_cnt,4," ") ORDER BY _h SEPARATOR " ") AS `. 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23` FROM ( SELECT FROM_UNIXTIME(last_access_epoch,"%Y-%m-%d") AS _d , FROM_UNIXTIME(last_access_epoch,"%H") AS _h , COUNT(*) AS _cnt FROM login_log WHERE last_access_epoch < 3600*(@@timestamp DIV 3600) /* before current hour */ GROUP BY _d, _h ) AS t GROUP BY _d HAVING MIN(_h)="00" /* only full days */ ;
MySQL Crosstab in a view, Part of your problem is your table structure. Unfortunately MySQL does not have a PIVOT/UNPIVOT function so you will need to do this with a UNION ALL and� Like the SELECT query, a crosstab query retrieves information from our database tables and presents it. However, the results of the crosstab query are displayed more like a spreadsheet, with row headers and column headers. Let’s see how we can use a crosstab query to get data in the crosstab results. Example
If you have a large amount of data for the GROUP_CONCAT example above, you may need to change your group_concat_max_len to avoid a syntax error due to truncation.
SET SESSION group_concat_max_len=4096;
See: Trouble with GROUP_CONCAT and Longtext in MySQL
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All About the Crosstab Query, A cross tabulation query, or cross tab for short, is used to display the Although I will be working in MySQL, the techniques discussed here� Crosstab View in mySQL? Ask Question Asked 7 years, 3 months ago. Active 6 months ago. Viewed 13k times 2. I dont know I titled this correct, but let me explain what
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- Try to check this links: stackoverflow.com/questions/2852708/… OR stackoverflow.com/questions/4336985/…. The first one is good if the row-to-column values are known and the second one is you use GROUP_CONCAT but it will not make your rows into column actually.
- I was thinking more in terms of a view. May be there could be a procedure that deletes a view and recreates it view when a new client is added.
- Awesome trick but with big table with a lot of data, it's too heavy :/
- @Thermech I agree, with a large amount of data there are different ways that this could be done.