Understanding PIVOT function in T-SQL

pivot, sql-server, sql-server-2008, t-sql

Solution

A `PIVOT` used to rotate the data from one column into multiple columns.

For your example here is a STATIC Pivot meaning you hard code the columns that you want to rotate:

create table temp
(
  id int,
  teamid int,
  userid int,
  elementid int,
  phaseid int,
  effort decimal(10, 5)
)

insert into temp values (1,1,1,3,5,6.74)
insert into temp values (2,1,1,3,6,8.25)
insert into temp values (3,1,1,4,1,2.23)
insert into temp values (4,1,1,4,5,6.8)
insert into temp values (5,1,1,4,6,1.5)

select elementid
  , [1] as phaseid1
  , [5] as phaseid5
  , [6] as phaseid6
from
(
  select elementid, phaseid, effort
  from temp
) x
pivot
(
  max(effort)
  for phaseid in([1], [5], [6])
)p

Here is a SQL Demo with a working version.

This can also be done through a dynamic PIVOT where you create the list of columns dynamically and perform the PIVOT.

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX);

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.phaseid) 
            FROM temp c
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT elementid, ' + @cols + ' from 
            (
                select elementid, phaseid, effort
                from temp
           ) x
            pivot 
            (
                 max(effort)
                for phaseid in (' + @cols + ')
            ) p '


execute(@query)

The results for both:

ELEMENTID   PHASEID1    PHASEID5    PHASEID6
3           Null        6.74        8.25
4           2.23        6.8         1.5

Problem

I am very new to SQL. I have a table like this: ID TeamID UserID ElementID PhaseID Effort 1 1 1 3 5 6.74 2 1 1 3 6 8.25 3 1 1 4 1 2.23 4 1 1 4 5 6.8 5 1 1 4 6 1.5 And I was told to get data like this ElementID PhaseID1 PhaseID5 PhaseID6 3 NULL 6.74 8.25 4 2.23 6.8 1.5 I understand I need to use PIVOT function. But can't understand it clearly. It would be great help if somebody can explain it in above case.(or any alternatives if any)

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