How do I cross join the date to a selection?

问题

I need a query that will have the date, a user's name, and one of twelve operation_id's for that date. eg

operations
"id";"name";
"1";"LASER CUTTING"
"2";"DEBURR"
"3";"MACHINING"
"4";"BENDING"
"5";"PEM"
"6";"WELDING"
"7";"PAINT PREPARATION"
"8";"PAINTING"
"9";"SILKSCREEN PREPARATION"
"10";"SILKSCREEN"
"11";"ASSEMBLY - PACKAGING"
"12";"LASER PREP";

and a users table

bob
jimmeh
jimbo

I have a cross join between those tables to get something like this:

bob 1
bob 2
bob 3
bob 4
bob 5
bob 6
bob 7
bob 8
bob 9
bob 10
bob 11
bob 12
jimmeh 1
jimmeh 2
jimmeh 3
jimmeh 4
jimmeh 5
jimmeh 6
jimmeh 7
jimmeh 8
jimmeh 9
jimmeh 10
jimmeh 11
jimmeh 12
jimbo 1
jimbo 2
jimbo 3
jimbo 4
jimbo 5
jimbo 6
jimbo 7
jimbo 8
jimbo 9
jimbo 10
jimbo 11
jimbo 12

But I would also like to cross join every day between January 1st of 2011 and now so that I can use this query to give me a record for every person for every operation for every day so that I can put it in a pivot table and then use that to drive a report for each week for each user for each operation.

As of now I have a simple select userid from db.users join operations where departmentid = 8

I tried this:

select 
  userid, 
    first_name, 
    last_name,
    operations.id,
    operations.name
from 
  protocase.tblusers 
join
  operations
join
  select (BETWEEN "2011-01-01" and NOW())
where 
  departmentid = 8 and 
    protocase.tblusers.active = 1

Similar to how one would select (1,2,3) or something else that's not from a table, but I can't seem to figure out how I would select all the dates between January 1st and now. Is this even possible?

回答1:

You could create a date table like this http://www.techrepublic.com/blog/datacenter/simplify-sql-server-2005-queries-with-a-dates-table/326

Edit: Added stored procedure to generate dates:

DROP PROCEDURE IF EXISTS datePopulate;
DELIMITER $$
CREATE PROCEDURE datePopulate( startDate datetime, numDays int)
BEGIN

declare currDate datetime default startDate;
declare i int default 1;

WHILE (i<=numDays) DO       

    INSERT INTO DateLookup(DateFull, fullYear, weekdayname) 
    VALUES(currDate, date_format(currDate, '%Y'), date_format(currDate, '%a'));
    SET i = i+1;
    SET currDate = DATE_ADD(currDate , INTERVAL 1 DAY);

END WHILE;

END $$
DELIMITER ;

Once procedure is created, it can be called like this:

CALL datePopulate('2011-01-01', 30);

This will populate the table with 30 days starting at 2011-01-01.

I didn't add all the columns in the insert statement. Should be pretty straight forward to add though using information from here.

回答2:

The simplest way is to have a pre-defined table with all the dates in the year, that will be 365 rows max. You can then simply use that table in your query selecting only rows between 2011-01-01 and NOW(). This will also mean that your query will have to do a lesser job by not creating a date table on every run.

Just another thought, though I'm not sure if you'll need this. If the intent is to have a date table for every year, for example in 2012 you would like a similar date table but with all dates from 2012, then you might consider storing only the date and month without the year.

Hope this makes sense.

来源：https://stackoverflow.com/questions/6613189/how-do-i-cross-join-the-date-to-a-selection

标签

mysql

sql

excel

cross-join