Dynamically create columns in SQL select query and join tables - sql

Question

I have 2 tables. They are as follows
Table : Grade
GradeID | Grade
-----------------
1 | Chopsaw
2 | Classic
3 | Chieve
Table : Moulded Quantity
Batch ID | Grade | Moulded | Date
-------------------------------------
1 | 1 | 150 | 21st May
2 | 1 | 150 | 22nd May
3 | 2 | 150 | 21st May
4 | 2 | 150 | 21st May
5 | 2 | 150 | 22nd May
I should get the Output like the following
Date | Moulded | Chopsaw | Classic | Cieve
--------------------------------------------------
21st May | 450 | 150 | 300 | 0
22nd May | 300 | 150 | 150 | 0
I am using MSSQL 2008 and i use Crystal report to display the same.

Answer 1

If the number of grades is known beforehand then you can do it with a static query.
SELECT date,
SUM(moulded) moulded,
SUM(CASE WHEN grade = 1 THEN moulded ELSE 0 END) Chopsaw,
SUM(CASE WHEN grade = 2 THEN moulded ELSE 0 END) Classic,
SUM(CASE WHEN grade = 3 THEN moulded ELSE 0 END) Chieve
FROM moulded_quantity
GROUP BY date
This query is not vendor specific so it should work on any major RDBMS.
Now, if the number of grades is unknown or you want it to work even if you make changes to grade table (without changing the query itself) you can resort to dynamic query. But dynamic SQL is vendor specific. Here is an example of how you can do that in MySql
SELECT CONCAT (
'SELECT date, SUM(moulded) moulded,',
GROUP_CONCAT(DISTINCT
CONCAT('SUM(CASE WHEN grade = ',gradeid,
' THEN moulded ELSE 0 END) ', grade)),
' FROM moulded_quantity GROUP BY date') INTO #sql
FROM grade;
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
Output (in both cases):
| DATE | MOULDED | CHOPSAW | CLASSIC | CHIEVE |
---------------------------------------------------
| 21st May | 450 | 150 | 300 | 0 |
| 22nd May | 300 | 150 | 150 | 0 |
Here is SQLFiddle demo (for both approaches).
UPDATE In Sql Server you can use STUFF and PIVOT to produce expected result with dynamic sql
DECLARE #colx NVARCHAR(MAX), #colp NVARCHAR(MAX), #sql NVARCHAR(MAX)
SET #colx = STUFF((SELECT ', ISNULL(' + QUOTENAME(Grade) + ',0) ' + QUOTENAME(Grade)
FROM grade
ORDER BY GradeID
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)'),1,1,'')
SET #colp = STUFF((SELECT DISTINCT ',' + QUOTENAME(Grade)
FROM grade
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)'),1,1,'')
SET #sql = 'SELECT date, total moulded, ' + #colx +
' FROM
(
SELECT date, g.grade gradename, moulded,
SUM(moulded) OVER (PARTITION BY date) total
FROM moulded_quantity q JOIN grade g
ON q.grade = g.gradeid
) x
PIVOT
(
SUM(moulded) FOR gradename IN (' + #colp + ')
) p
ORDER BY date'
EXECUTE(#sql)
Output is the same as in MySql case.
Here is SQLFiddle demo.

Answer 2

I would suggest you before asking any question research first as it is very common question.
Updated
DECLARE #COLUMNS varchar(max)
SELECT #COLUMNS = COALESCE(#COLUMNS+'],[' ,'') + CAST(Grade as varchar)
FROM Grade
GROUP BY Grade
SET #COLUMNS = '[' + #COLUMNS + ']'
DECLARE #COLUMNS_WITH_NULL varchar(max)
SELECT #COLUMNS_WITH_NULL = COALESCE(#COLUMNS_WITH_NULL+',ISNULL([' ,'ISNULL([') + CAST(Grade as varchar) + '], 0) AS ' + CAST(Grade as varchar)
FROM Grade
GROUP BY Grade
DECLARE #COLUMNS_SUMS varchar(max)
SELECT #COLUMNS_SUMS = COALESCE(#COLUMNS_SUMS+' + ISNULL([' ,'ISNULL([') + CAST(Grade as varchar) + '], 0) '
FROM Grade
GROUP BY Grade
SET #COLUMNS_SUMS = '(' + #COLUMNS_SUMS + ') as Moulded'
PRINT #COLUMNS_SUMS
EXECUTE (
'
SELECT
Date, ' + #COLUMNS_SUMS + ', ' + #COLUMNS_WITH_NULL + '
FROM (
SELECT
m.Moulded,
m.date AS Date,
g.Grade
FROM Grade g
INNER JOIN [Moulded Quantity] m
ON m.GRADE = g.GradeID
) up
PIVOT (SUM(Moulded) FOR Grade IN ('+ #COLUMNS +')) AS pvt')