Creating new columns in Sql Server based on other columns - sql

Question

I have a table T :
CREATE TABLE T
(
id INT,
type VARCHAR(200),
type_value VARCHAR(10),
value VARCHAR(200)
);
INSERT INTO T VALUES (1, 'HomePhone', 'p1', '1234 ');
INSERT INTO T VALUES (1, 'HomePhone', 'p2', '5678 ');
INSERT INTO T VALUES (1, 'HomePhone', 'p3', '4567');
INSERT INTO T VALUES (1, 'WorkPhone', 'w1', '9007 ');
INSERT INTO T VALUES (2, 'Email', 'e1', 'abc#xyz.com ');
INSERT INTO T VALUES (2, 'Email', 'e1', 'efg#xyz.com');
INSERT INTO T VALUES (2, 'Email', 'e2', 'mno#xyz.com');
INSERT INTO T VALUES (3, 'WorkPhone', 'w1', '0100');
INSERT INTO T VALUES (3, 'WorkPhone', 'w2', '0110');
INSERT INTO T VALUES (4, 'OtherPhone', 'o1', '1010 ');
INSERT INTO T VALUES (4, 'OtherPhone', 'o1', '1110 ');
INSERT INTO T VALUES (4, 'OtherPhone', 'o1', '1011');
INSERT INTO T VALUES (4, 'HomePhone', 'p1', '2567 ');
I need to transform it into :
id primaryhomephone secondaryhomephone primaryemail secondaryemail Primaryworkphone secondaryworkphone primaryotherphone secondaryotherphone
----------------------------------------------------------------------------------------------------------------------------------------------------------------
1 1234 5678 null null 9007 null null null
2 null null abc#xyz.com efg#xyz.com null null null null
3 null null null null 0100 0110 null null
4 2567 null null null null null 1010 1011
Basically the field will be divided based on type_value. If there is two type_value for same id and type then first type will be primary and second type will be secondary.
For more than two type values for same id and type, discard the third one.
For more than two type values of same type(for example o1,o1) for id 4 first o1 will be primaryotherphone and second one will be secondaryprimaryphone.
Sorry if this question has been repeated before but somehow I can't solve it. Can anyone please help. Thanks a lot

Answer 1

You can use MAX/GROUP BY technique. PIVOT is quite complex for beginners, but I agree that the purpose of the PIVOT is the exactly what you need:
SELECT id
, MAX(CASE WHEN type_value = 'p1' THEN value END ) AS primaryhomephone
, MAX(CASE WHEN type_value = 'p2' THEN value END ) AS secondaryhomephone
, MAX(CASE WHEN type_value = 'p3' THEN value END ) AS thirdphone
, MAX(CASE WHEN type_value = 'w1' THEN value END ) AS workphone
, MAX(CASE WHEN type_value = 'w2' THEN value END ) AS secondaryworkphone
, MAX(CASE WHEN type_value = 'o2' THEN value END ) AS otherworkphone
, MAX(CASE WHEN type_value = 'e1' THEN value END ) AS primaryemail
, MAX(CASE WHEN type_value = 'e2' THEN value END ) AS secondaryemail
FROM T
GROUP BY id
;

Answer 2

You need to look after computed columns in SQL Server.
CREATE TABLE [dbo].T
(
...
[primaryhomephone] AS (CASE WHEN type_value = 'p1' THEN value ELSE NULL END)
)
Alternatively you can use Views:
CREATE VIEW dbo.vwT
AS
SELECT
id
,(CASE WHEN type_value = 'p1' THEN value ELSE NULL END as [primaryhomephone]
, (CASE WHEN type_value = 'p2' THEN value ELSE NULL END as [secondaryhomephone]
FROM dbo.T

Answer 3

You need to look into PIVOT Column presentation. You can use it in to ways, you can create new Table with your column and then use PIVOT Query to insert them there, or you can simply fetch at runtime. If there is lot of data and all other Programming interface are ready to upgrade then make new table, else just use query.
Here is the link for your reference: https://technet.microsoft.com/en-us/library/ms177410(v=sql.105).aspx