Pivot Table Omitting Rows that Have Null values

问题

I am solving a problem very similar to this only in my case, I am not summing any values.
I have been able to write a select that works using solution from this page

SELECT 
  id, 
  GROUP_CONCAT(if(colID = 1, value, NULL)) AS 'First Name',
  GROUP_CONCAT(if(colID = 2, value, NULL)) AS 'Last Name',
  GROUP_CONCAT(if(colID = 3, value, NULL)) AS 'Job Title'
FROM tbl
GROUP BY id;

However, I want to omit rows that have the value to be null

回答1:

I assume you want to drop the result row if any of the source rows has value IS NULL.
You should be able to achieve that with bit_and() in the HAVING clause:

SELECT id
     , max(CASE WHEN colID = 1 THEN value END) AS fn
     , max(CASE WHEN colID = 2 THEN value END) AS ln
     , max(CASE WHEN colID = 3 THEN value END) AS jt
FROM   tbl 
GROUP  BY id
HAVING bit_and(value IS NOT NULL);

Alternative:

...
HAVING count(*) = count(value);

I didn't spell out ELSE NULL in the CASE statements because (per documentation):

If there was no matching result value, the result after ELSE is returned, or NULL if there is no ELSE part.

回答2:

Just add this constraint to the where statement of your query, like this:

SELECT 
  id, 
  GROUP_CONCAT(if(colID = 1, value, NULL)) AS 'First Name',
  GROUP_CONCAT(if(colID = 2, value, NULL)) AS 'Last Name',
  GROUP_CONCAT(if(colID = 3, value, NULL)) AS 'Job Title'
FROM tbl
WHERE value IS NOT NULL
GROUP BY id;

EDIT

After some tests I could make a solution to work, but it seems interesting why value is not null won't work.

Solution link: http://sqlfiddle.com/#!2/b7a445/3

SELECT 
  id, 
  max(case when colID = 1 then value else '' end) AS fn,
  max(case when colID = 2 then value else '' end) AS ln,
  max(case when colID = 3 then value else '' end) AS jt
FROM tbl 
where not exists (select * from tbl b where tbl.id=b.id and value is null)
group by id

来源：https://stackoverflow.com/questions/26516906/pivot-table-omitting-rows-that-have-null-values

标签

mysql

pivot-table

group-concat