Query using dynamic column names

Hi All,
I have a table DATA with following 20 columns.
COL1, COL2, COL3, COL4,..... COL20
Another table TEMPLATE has one column COLNAME. The table contains 5 rows with the data COL2, COL5, COL6, COL9, COL12 in the column COLNAME.
Can someone help me to build sql statement to select data from DATA table for only columns listed in the TEMPLATE table. I want to do this using only one select statement. (I know how to do this with stored procedure but thats not what I want)
Also it is possible that row in TEMPLATE table may change.
Hope to get some positive replies.
Reagrds,
HK
If all the columns are of compatible types then you can do it like this:
CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGER
NOT NULL UNIQUE)
INSERT INTO Template VALUES ('COL1',1)
INSERT INTO Template VALUES ('COL2',2)
INSERT INTO Template VALUES ('COL3',3)
SELECT MIN(CASE
WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
/* .. etc */
END),
MIN(CASE
WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
END),
MIN(CASE
WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
END),
...
FROM Data AS D
CROSS JOIN Template AS T
GROUP BY D.col1, D.col2, D.col3, ... other cols
Otherwise use IF statements or dynamic SQL. You could also consider building
the SELECT statement client-side or retrieve all the columns but display
only the required ones to the user.
David Portas
SQL Server MVP
|||Thanks for your help David. But this will not work for me. The example I gave was to explain my problem. But in reality, I will not know all column names in the DATA table, only TEMPLATE table is the guide which has list of fields to select from DATA tabl
e.
Regards,
HK
"David Portas" wrote:

> If all the columns are of compatible types then you can do it like this:
> CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGER
> NOT NULL UNIQUE)
> INSERT INTO Template VALUES ('COL1',1)
> INSERT INTO Template VALUES ('COL2',2)
> INSERT INTO Template VALUES ('COL3',3)
> SELECT MIN(CASE
> WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
> /* .. etc */
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
> END),
> ...
> FROM Data AS D
> CROSS JOIN Template AS T
> GROUP BY D.col1, D.col2, D.col3, ... other cols
> Otherwise use IF statements or dynamic SQL. You could also consider building
> the SELECT statement client-side or retrieve all the columns but display
> only the required ones to the user.
> --
> David Portas
> SQL Server MVP
> --
>
>

Query using dynamic column names

Hi All,
I have a table DATA with following 20 columns.
COL1, COL2, COL3, COL4,..... COL20
Another table TEMPLATE has one column COLNAME. The table contains 5 rows wi
th the data COL2, COL5, COL6, COL9, COL12 in the column COLNAME.
Can someone help me to build sql statement to select data from DATA table fo
r only columns listed in the TEMPLATE table. I want to do this using only on
e select statement. (I know how to do this with stored procedure but thats n
ot what I want)
Also it is possible that row in TEMPLATE table may change.
Hope to get some positive replies.
Reagrds,
HKIf all the columns are of compatible types then you can do it like this:
CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGER
NOT NULL UNIQUE)
INSERT INTO Template VALUES ('COL1',1)
INSERT INTO Template VALUES ('COL2',2)
INSERT INTO Template VALUES ('COL3',3)
SELECT MIN(CASE
WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
/* .. etc */
END),
MIN(CASE
WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
END),
MIN(CASE
WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
END),
..
FROM Data AS D
CROSS JOIN Template AS T
GROUP BY D.col1, D.col2, D.col3, ... other cols
Otherwise use IF statements or dynamic SQL. You could also consider building
the SELECT statement client-side or retrieve all the columns but display
only the required ones to the user.
David Portas
SQL Server MVP
--|||Thanks for your help David. But this will not work for me. The example I gav
e was to explain my problem. But in reality, I will not know all column name
s in the DATA table, only TEMPLATE table is the guide which has list of fiel
ds to select from DATA tabl
e.
Regards,
HK
"David Portas" wrote:

> If all the columns are of compatible types then you can do it like this:
> CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGE
R
> NOT NULL UNIQUE)
> INSERT INTO Template VALUES ('COL1',1)
> INSERT INTO Template VALUES ('COL2',2)
> INSERT INTO Template VALUES ('COL3',3)
> SELECT MIN(CASE
> WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
> /* .. etc */
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
> END),
> ...
> FROM Data AS D
> CROSS JOIN Template AS T
> GROUP BY D.col1, D.col2, D.col3, ... other cols
> Otherwise use IF statements or dynamic SQL. You could also consider buildi
ng
> the SELECT statement client-side or retrieve all the columns but display
> only the required ones to the user.
> --
> David Portas
> SQL Server MVP
> --
>
>

Query using dynamic column names

Hi All,
I have a table DATA with following 20 columns.
COL1, COL2, COL3, COL4,..... COL20
Another table TEMPLATE has one column COLNAME. The table contains 5 rows with the data COL2, COL5, COL6, COL9, COL12 in the column COLNAME.
Can someone help me to build sql statement to select data from DATA table for only columns listed in the TEMPLATE table. I want to do this using only one select statement. (I know how to do this with stored procedure but thats not what I want)
Also it is possible that row in TEMPLATE table may change.
Hope to get some positive replies.
Reagrds,
HKIf all the columns are of compatible types then you can do it like this:
CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGER
NOT NULL UNIQUE)
INSERT INTO Template VALUES ('COL1',1)
INSERT INTO Template VALUES ('COL2',2)
INSERT INTO Template VALUES ('COL3',3)
SELECT MIN(CASE
WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
/* .. etc */
END),
MIN(CASE
WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
END),
MIN(CASE
WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
END),
...
FROM Data AS D
CROSS JOIN Template AS T
GROUP BY D.col1, D.col2, D.col3, ... other cols
Otherwise use IF statements or dynamic SQL. You could also consider building
the SELECT statement client-side or retrieve all the columns but display
only the required ones to the user.
--
David Portas
SQL Server MVP
--|||Thanks for your help David. But this will not work for me. The example I gave was to explain my problem. But in reality, I will not know all column names in the DATA table, only TEMPLATE table is the guide which has list of fields to select from DATA table.
Regards,
HK
"David Portas" wrote:
> If all the columns are of compatible types then you can do it like this:
> CREATE TABLE Template (colname VARCHAR(10) PRIMARY KEY, ordinal_pos INTEGER
> NOT NULL UNIQUE)
> INSERT INTO Template VALUES ('COL1',1)
> INSERT INTO Template VALUES ('COL2',2)
> INSERT INTO Template VALUES ('COL3',3)
> SELECT MIN(CASE
> WHEN T.ordinal_pos = 1 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 1 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 1 AND T.colname='col3' THEN col3
> /* .. etc */
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 2 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 2 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 2 AND T.colname='col3' THEN col3
> END),
> MIN(CASE
> WHEN T.ordinal_pos = 3 AND T.colname='col1' THEN col1
> WHEN T.ordinal_pos = 3 AND T.colname='col2' THEN col2
> WHEN T.ordinal_pos = 3 AND T.colname='col3' THEN col3
> END),
> ...
> FROM Data AS D
> CROSS JOIN Template AS T
> GROUP BY D.col1, D.col2, D.col3, ... other cols
> Otherwise use IF statements or dynamic SQL. You could also consider building
> the SELECT statement client-side or retrieve all the columns but display
> only the required ones to the user.
> --
> David Portas
> SQL Server MVP
> --
>
>

Query to get all user tables with columns

Hi,

I tried to create a simple view as follows

CREATE VIEW V_ALL_USERTABLE_COLUMNS
AS
(
SELECT
OBJ.NAME as TableName,
COL.NAME as ColName,
TYP.NAME AS TYPE

FROM
SYSOBJECTS OBJ,
SYSCOLUMNS COL,
SYSTYPES TYP

WHERE
OBJ.TYPE = 'U'
AND OBJ.ID = COL.ID
AND COL.TYPE = TYP.TYPE
)

Combined with consistent naming conventions I will use this view to
easily find foreign keys; a la

SELECT *
FROM V_ALL_USERTABLE_COLUMNS
WHERE ColName LIKE ('%user_id')

There is something wrong with my view definition that I don't get
though; it doesn't return all the columns. I have a table with the
following definition

CREATE TABLE [dbo].[c_messages]
(
[cid] [int] IDENTITY (1, 1) NOT NULL ,
[touser_id] [int] NULL ,
[tosession_id] [char] (32) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
,
[fromuser_id] [int] NOT NULL ,
[message] [varchar] (255) COLLATE SQL_Latin1_General_CP1_CI_AS NOT
NULL ,
[message_read] [bit] NOT NULL ,
[logout] [bit] NULL
) ON [PRIMARY]
GO

The problem is that the select I used to define the view doesn't
return the touser_id column. I have sort of a sneaking suspicion that
the problem has to do with joining syscolumns.type to systypes.type,
but I don't know what to do instead (I'd really like to include the
type; it's useful if I ever changed the type of a primary key and want
to check that I also changed all the foreign keys).

Any help would be appreciated!Use the information schema rather than the system tables:

SELECT * FROM information_schema.columns

This format is much easier to use.

Your original query should work if you join on XTYPE rather than TYPE
but this is not recommended. In general you should avoid referencing
system tables directly.

--
David Portas
SQL Server MVP
--