Say we have a table:
CREATE TABLE new_table
(
regionname character varying(10),
year integer,
month integer,
value integer
)
How to select for example the 3rd column "month" without using
SELECT month FROM new_table
but something like
SELECT "the 3rd column" FROM new_table
I want to first say that a table schema could change, so the column order could change, thus breaking any existing queries, stored procedures, or code outside your database. What exactly are you trying to accomplish? Do you just want to use numbers instead of names?
This answer:
Declare #WhichOne int;
Declare #Sql varchar(200);
Set #WhichOne = 2;
With cte As
(Select name, Row_Number() Over (Order By column_id) As rn
From sys.columns
Where Object_Name(object_id) = 'MyTable')
Select #Sql = 'Select ' + QuoteName(name) + ' From MyTable'
From cte
Where rn = #WhichOne;
Exec(#Sql);
Can be found here: http://www.codeproject.com/Questions/148495/Solved-SELECT-columns-by-column-index-NOT-by-colu
Related
I currently have a query which I am using to unpivot an existing table.
Some background information on the table - each year a new column is added to the table to indicate the $ values for a project ID for that year. With every column added one will be dropped. All these columns are prefixed with 'YR_' followed by the new year. There are constantly 20 'YR_' columns.
I am required to unpivot the 'YR_' columns so that they appear as per below, allowing me to utilize the information easier for several reports -
Before unpivot -
ProjectID YR_16 YR_17 YR_18 YR_19 YR_20
10 0 100 20 25 100
After unpivot -
ProjectID YR Value
10 YR_16 0
10 YR_17 100
10 YR_18 20
10 YR_19 25
10 YR_20 100
Below is the query I am using to create the unpivot table, which will dynamically pick up columns as they are added/dropped
declare #query as NVARCHAR(max);
Declare #cols as NVARCHAR(250) = STUFF((
Select distinct ',' + QUOTENAME(Column_Name)
From INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'F1BWK_PLM_CAPEX'
And COLUMN_NAME like 'YR_%'
For XML Path(''), type)
.value('.','NVARCHAR(MAX)')
,1,1,'');
Select #query = 'With Unpivoted as
(
Select * from F1BWK_PLM_CAPEX U
Unpivot (
Val
For Yr in (' + #cols + ')
)
As UnpivotTable
)
Select U.*
From Unpivoted U
inner join [dbo].[F1_SYPAR_CTL] CTL
on CTL.value = U.WS_VERS
and CTL.PARAM_NAME like ''MBRC_CURR_PLM_BUDVER''
inner join [dbo].[F1_SYPAR_CTL] CTL2
on CTL2.value = U.WS_NAME
and CTL2.PARAM_NAME like ''MBRC_CURR_PLM_BUDWSH''';
Exec(#query);
I am having issues in turning this query into a function so that I can call upon it and save it in SQL Server so that other members of my team can use it when they require it.
This is my first time using unpivot tables and creating functions. Open to suggestions on changing my dynamic unpivot query to best suits my needs.
Thanks in advance
In SQL Server you are not allowed to have dynamic SQL in functions.
You can create an SP that will return a record set generated using your code above.
UPDATE:
For the sake of completeness:
You can also call the above SP using (OPENQUERY) which would allow you to join to other tables without having to save to a temp table first but IMO it is an ugly way do this.
END UPDATE:
Another way is to create a VIEW that would un-pivot this table and create an SP that would regenerate this view after the process that adds a new column is completed e.g.
CREATE TABLE F1BWK_PLM_CAPEX( Val INT, Yr_17 INT, Yr_18 INT )
INSERT INTO F1BWK_PLM_CAPEX
SELECT 1, 10, 12
CREATE VIEW F1BWK_PLM_CAPEX_UNPIVOTED
AS
SELECT *
FROM F1BWK_PLM_CAPEX AS U
UNPIVOT (
Val2 FOR Yr IN (Yr_17, Yr_18)
)
AS UnpivotTable;
CREATE PROCEDURE dbo.Create_F1BWK_PLM_CAPEX_UNPIVOTED
AS
SET NOCOUNT ON
DECLARE #query as NVARCHAR(max);
DECLARE #cols as NVARCHAR(250) =
STUFF((
SELECT distinct ',' + QUOTENAME( Column_Name )
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'F1BWK_PLM_CAPEX'
AND COLUMN_NAME like 'YR_%'
For XML Path(''), type)
.value('.','NVARCHAR(MAX)' )
,1,1,'');
SELECT #query = '
ALTER VIEW F1BWK_PLM_CAPEX_UNPIVOTED
AS
SELECT *
FROM F1BWK_PLM_CAPEX AS U
UNPIVOT (
Val2 FOR Yr IN ( ' + #cols + ' )
)
AS UnpivotTable
';
EXEC(#query);
RETURN;
Now your query would become this:
SELECT *
FROM F1BWK_PLM_CAPEX_UNPIVOTED AS U
INNER JOIN [dbo].[F1_SYPAR_CTL] AS CTL
ON CTL.value = U.WS_VERS and CTL.PARAM_NAME = 'MBRC_CURR_PLM_BUDVER'
INNER JOIN [dbo].[F1_SYPAR_CTL] AS CTL2
ON CTL2.value = U.WS_NAME AND CTL2.PARAM_NAME = 'MBRC_CURR_PLM_BUDWSH'
At the end of the year a process runs that adds a new column:
ALTER TABLE F1BWK_PLM_CAPEX
ADD Yr_19 INT NOT NULL DEFAULT( 10 )
This process needs to run this SP to regenerate the view:
EXEC Create_F1BWK_PLM_CAPEX_UNPIVOTED
Notes:
I have replaced LIKE with = as your query matches on a full value. Only use LIKE when you need to specify wild cards.
I have also fixed a syntax error by changing Val to Val2 in the UNPIVOT query
Is there a way to access columns by their index within a stored procedure in SQL Server?
The purpose is to compute lots of columns. I was reading about cursors, but I do not know how to apply them.
Let me explain my problem:
I have a row like:
field_1 field_2 field_3 field_4 ...field_d Sfield_1 Sfield_2 Sfield_3...Sfield_n
1 2 3 4 d 10 20 30 n
I need to compute something like (field_1*field1) - (Sfield_1* Sfiled_1) / more...
So the result is stored in a table column d times.
So the result is a d column * d row table.
As the number of columns is variable, I was considering making dynamic SQL, getting the names of columns in a string and splitting the ones I need, but this approach makes the problem harder. I thought getting the column number by index could make life easier.
No, you can not use the ordinal (numeric) position in the SELECT clause.
Only in the ORDER BY clause can you use the ordinal position, because it's based on the column(s) specified in the SELECT clause.
First, as OMG Ponies stated, you cannot reference columns by their ordinal position. This is not an accident. The SQL specification is not built for dynamic schema either in DDL or DML.
Given that, I have to wonder why you have your data structured as you do. A sign of a mismatch between schema and the problem domain rears itself when you try to extract information. When queries are incredibly cumbersome to write, it is an indication that the schema does not properly model the domain for which it was designed.
However, be that as it may, given what you have told us, an alternate solution would be something like the following: (I'm assuming that field_1*field1 was meant to be field_1 * field_1 or field_1 squared or Power( field_1, 2 ) )
Select 1 As Sequence, field_1 As [Field], Sfield_1 As [SField], Sfiled_1 As [SFiled]
Union All Select 2, field_2, Sfield_2, Sfiled_2
...
Union All Select n, field_n, Sfield_n, Sfiled_n
Now your query looks like:
With Inputs As
(
Select 1 As Sequence, field_1 As [Field], Sfield_1 As [SField], Sfiled_1 As [SFiled]
Union All Select 2, field_2, Sfield_2, Sfiled_2
....
)
, Results As
(
Select Case
When Sequence = 1 Then Power( [Field], 2 ) - ( [SField] * [SFiled] )
Else 1 / Power( [Field], 2 ) - ( [SField] * [SFiled] )
End
As Result
From Inputs
)
Select Exp( Sum( Log( Result ) ) )
From Results
This might not be the most elegant or efficient but it works. I am using it to create a new table for faster mappings between data that I need to parse through all the columns / rows.
DECLARE #sqlCommand varchar(1000)
DECLARE #columnNames TABLE (colName varchar(64), colIndex int)
DECLARE #TableName varchar(64) = 'YOURTABLE' --Table Name
DECLARE #rowNumber int = 2 -- y axis
DECLARE #colNumber int = 24 -- x axis
DECLARE #myColumnToOrderBy varchar(64) = 'ID' --use primary key
--Store column names in a temp table
INSERT INTO #columnNames (colName, colIndex)
SELECT COL.name AS ColumnName, ROW_NUMBER() OVER (ORDER BY (SELECT 1))
FROM sys.tables AS TAB
INNER JOIN sys.columns AS COL ON COL.object_id = TAB.object_id
WHERE TAB.name = #TableName
ORDER BY COL.column_id;
DECLARE #colName varchar(64)
SELECT #colName = colName FROM #columnNames WHERE colIndex = #colNumber
--Create Dynamic Query to retrieve the x,y coordinates from table
SET #sqlCommand = 'SELECT ' + #colName + ' FROM (SELECT ' + #colName + ', ROW_NUMBER() OVER (ORDER BY ' + #myColumnToOrderBy+ ') AS RowNum FROM ' + #tableName + ') t2 WHERE RowNum = ' + CAST(#rowNumber AS varchar(5))
EXEC(#sqlCommand)
I am trying to create a dynamic SQL statement that includes an alias that has to increment. My query is like
DECLARE #q varchar(255)
SET #q = '0'
SELECT 'SELECT (SELECT DISTINCT NameColumn
FROM NAMETABLE) #q'
FROM NameTable
Where for each record in nametable #q changes. So it would go #q = 0 for record 1, #q = 1 for record 2, #q = 2 for record 3, etc. I found ROW_NUMBER but that appears to only do incrementing a column and as an Int whereas I need a varchar to increment. If someone had an idea as to how to do this or could point me in the right direction that would be wonderful
Is this what you want?
SELECT 'SELECT (SELECT DISTINCT NameColumn
FROM NAMETABLE
) ' + cast(row_number() over (order by (select NULL)) as varchar(255))
FROM NameTable;
I am, however, unclear on why you would want an alias to be a number.
EDIT:
To get what you want, just pre-pend the number with a letter.
SELECT 'SELECT (SELECT DISTINCT NameColumn
FROM NAMETABLE
) t' + cast(row_number() over (order by (select NULL)) as varchar(255))
FROM NameTable;
I'm looking for a schema-independent query. That is, if I have a users table or a purchases table, the query should be equally capable of catching duplicate rows in either table without any modification (other than the from clause, of course).
I'm using T-SQL, but I'm guessing there should be a general solution.
I believe that this should work for you. Keep in mind that CHECKSUM() isn't 100% perfect - it's theoretically possible to get a false positive here (I think), but otherwise you can just change the table name and this should work:
;WITH cte AS (
SELECT
*,
CHECKSUM(*) AS chksum,
ROW_NUMBER() OVER(ORDER BY GETDATE()) AS row_num
FROM
My_Table
)
SELECT
*
FROM
CTE T1
INNER JOIN CTE T2 ON
T2.chksum = T1.chksum AND
T2.row_num <> T1.row_num
The ROW_NUMBER() is needed so that you have some way of distinguishing rows. It requires an ORDER BY and that can't be a constant, so GETDATE() was my workaround for that.
Simply change the table name in the CTE and it should work without spelling out the columns.
I'm still confused about what "detecting them might be" but I'll give it a shot.
Excluding them is easy
e.g.
SELECT DISTINCT * FROM USERS
However if you wanted to only include them and a duplicate is all the fields than you have to do
SELECT
[Each and every field]
FROM
USERS
GROUP BY
[Each and every field]
HAVING COUNT(*) > 1
You can't get away with just using (*) because you can't GROUP BY *
so this requirement from your comments is difficult
a schema-independent means I don't want to specify all of the columns
in the query
Unless that is you want to use dynamic SQL and read the columns from sys.columns or information_schema.columns
For example
DECLARE #colunns nvarchar(max)
SET #colunns = ''
SELECT #colunns = #colunns + '[' + COLUMN_NAME +'], '
FROM INFORMATION_SCHEMA.columns
WHERE table_name = 'USERS'
SET #colunns = left(#colunns,len(#colunns ) - 1)
DECLARE #SQL nvarchar(max)
SET #SQL = 'SELECT ' + #colunns
+ 'FROM USERS' + 'GROUP BY '
+ #colunns
+ ' Having Count(*) > 1'
exec sp_executesql #SQL
Please note you should read this The Curse and Blessings of Dynamic SQL if you haven't already
I have done this using CTEs in SQL Server.
Here is a sample on how to delete dupes but you should be able to adapt it easily to find dupes:
WITH CTE (COl1, Col2, DuplicateCount)
AS
(
SELECT COl1,Col2,
ROW_NUMBER() OVER(PARTITION BY COl1,Col2 ORDER BY Col1) AS DuplicateCount
FROM DuplicateRcordTable
)
DELETE
FROM CTE
WHERE DuplicateCount > 1
GO
Here is a link to an article where I got the SQL:
http://blog.sqlauthority.com/2009/06/23/sql-server-2005-2008-delete-duplicate-rows/
I recently was looking into the same issue and noticed this question.
I managed to solve it using a stored procedure with some dynamic SQL. This way you only need to specify the table name. And it will get all the other relevant data from sys tables.
/*
This SP returns all duplicate rows (1 line for each duplicate) for any given table.
to use the SP:
exec [database].[dbo].[sp_duplicates]
#table = '[database].[schema].[table]'
*/
create proc dbo.sp_duplicates #table nvarchar(50) as
declare #query nvarchar(max)
declare #groupby nvarchar(max)
set #groupby = stuff((select ',' + [name]
FROM sys.columns
WHERE object_id = OBJECT_ID(#table)
FOR xml path('')), 1, 1, '')
set #query = 'select *, count(*)
from '+#table+'
group by '+#groupby+'
having count(*) > 1'
exec (#query)
Is there a way to access columns by their index within a stored procedure in SQL Server?
The purpose is to compute lots of columns. I was reading about cursors, but I do not know how to apply them.
Let me explain my problem:
I have a row like:
field_1 field_2 field_3 field_4 ...field_d Sfield_1 Sfield_2 Sfield_3...Sfield_n
1 2 3 4 d 10 20 30 n
I need to compute something like (field_1*field1) - (Sfield_1* Sfiled_1) / more...
So the result is stored in a table column d times.
So the result is a d column * d row table.
As the number of columns is variable, I was considering making dynamic SQL, getting the names of columns in a string and splitting the ones I need, but this approach makes the problem harder. I thought getting the column number by index could make life easier.
No, you can not use the ordinal (numeric) position in the SELECT clause.
Only in the ORDER BY clause can you use the ordinal position, because it's based on the column(s) specified in the SELECT clause.
First, as OMG Ponies stated, you cannot reference columns by their ordinal position. This is not an accident. The SQL specification is not built for dynamic schema either in DDL or DML.
Given that, I have to wonder why you have your data structured as you do. A sign of a mismatch between schema and the problem domain rears itself when you try to extract information. When queries are incredibly cumbersome to write, it is an indication that the schema does not properly model the domain for which it was designed.
However, be that as it may, given what you have told us, an alternate solution would be something like the following: (I'm assuming that field_1*field1 was meant to be field_1 * field_1 or field_1 squared or Power( field_1, 2 ) )
Select 1 As Sequence, field_1 As [Field], Sfield_1 As [SField], Sfiled_1 As [SFiled]
Union All Select 2, field_2, Sfield_2, Sfiled_2
...
Union All Select n, field_n, Sfield_n, Sfiled_n
Now your query looks like:
With Inputs As
(
Select 1 As Sequence, field_1 As [Field], Sfield_1 As [SField], Sfiled_1 As [SFiled]
Union All Select 2, field_2, Sfield_2, Sfiled_2
....
)
, Results As
(
Select Case
When Sequence = 1 Then Power( [Field], 2 ) - ( [SField] * [SFiled] )
Else 1 / Power( [Field], 2 ) - ( [SField] * [SFiled] )
End
As Result
From Inputs
)
Select Exp( Sum( Log( Result ) ) )
From Results
This might not be the most elegant or efficient but it works. I am using it to create a new table for faster mappings between data that I need to parse through all the columns / rows.
DECLARE #sqlCommand varchar(1000)
DECLARE #columnNames TABLE (colName varchar(64), colIndex int)
DECLARE #TableName varchar(64) = 'YOURTABLE' --Table Name
DECLARE #rowNumber int = 2 -- y axis
DECLARE #colNumber int = 24 -- x axis
DECLARE #myColumnToOrderBy varchar(64) = 'ID' --use primary key
--Store column names in a temp table
INSERT INTO #columnNames (colName, colIndex)
SELECT COL.name AS ColumnName, ROW_NUMBER() OVER (ORDER BY (SELECT 1))
FROM sys.tables AS TAB
INNER JOIN sys.columns AS COL ON COL.object_id = TAB.object_id
WHERE TAB.name = #TableName
ORDER BY COL.column_id;
DECLARE #colName varchar(64)
SELECT #colName = colName FROM #columnNames WHERE colIndex = #colNumber
--Create Dynamic Query to retrieve the x,y coordinates from table
SET #sqlCommand = 'SELECT ' + #colName + ' FROM (SELECT ' + #colName + ', ROW_NUMBER() OVER (ORDER BY ' + #myColumnToOrderBy+ ') AS RowNum FROM ' + #tableName + ') t2 WHERE RowNum = ' + CAST(#rowNumber AS varchar(5))
EXEC(#sqlCommand)