How to Avoid Data Loss When Using PIVOT Queries on Distinct Records with Zero Values?

Avoiding Data Loss in PIVOT Queries for Distinct Records

Problem:
PIVOT queries are useful for restructuring data to display information in a more organized manner. However, when dealing with distinct records, the MAX aggregation function can cause zero values to be omitted, leading to incomplete data.

Solution:
To preserve all distinct records, even those with zero values, one can incorporate the ROW_NUMBER() function into the PIVOT query. This approach assigns a row number to each record, maintaining the association between activities and percentages.

;with cte as 
(
    select *, ROW_NUMBER() over (partition by name order by percentage desc) ROWNUM
    from A
),
cte2 as
(
    SELECT Id,Code,ROWNUM,James,James_,Sam,Sam_,Lisa,Lisa_
    FROM cte
    PIVOT(MAX(activity)
          FOR name IN (James,Sam,Lisa)) AS PVTTable PIVOT
          (
          MAX(percentage)
          FOR name1 IN (James_,Sam_,Lisa_)) AS PVTTable1
)
select Id, Code, MAX(James) James, MAX(James_) James_, MAX(Sam) Sam, MAX(Sam_) Sam_, MAX(Lisa) Lisa, MAX(Lisa_) Lisa_
from cte2
group by Id, Code, ROWNUM

Example:

Consider the following table:

Id	Code	percentage	name	name1	activity
1	Prashant	43.43	James	James_	Running
1	Prashant	70.43	Sam	Sam_	Cooking
1	Prashant	90.34	Lisa	Lisa_	Walking
1	Prashant	0.00	James	James_	Stealing
1	Prashant	0.00	James	James_	Lacking
1	Prashant	73	Sam	Sam_	Cooking 1

Previously, a standard PIVOT query would have produced the following result:

Id	Code	James	James_	Sam	Sam_	Lisa	Lisa_
1	Prashant	Running	43.43	Cooking 1	73	Walking	90.34
1	Prashant	Stealing	0.0	Cooking	3.43	NULL	NULL
1	Prashant	NULL	NULL	NULL	NULL	NULL	NULL

However, by incorporating the ROW_NUMBER() function, the modified query retains all distinct records:

Id	Code	James	James_	Sam	Sam_	Lisa	Lisa_
1	Prashant	Running	43.43	Cooking 1	73	Walking	90.34
1	Prashant	Stealing	0.00	Cooking	3.43	NULL	NULL
1	Prashant	Lacking	0.00	NULL	NULL	NULL	NULL

This approach ensures that all distinct activities are displayed, even those with zero percentage values, providing a more accurate representation of the data.

The above is the detailed content of How to Avoid Data Loss When Using PIVOT Queries on Distinct Records with Zero Values?. For more information, please follow other related articles on the PHP Chinese website!