I'm working on a database which has the following table:
id location
1 Singapore
2 Vancouver
3 Egypt
4 Tibet
5 Crete
6 Monaco
My question is, how can I produce a query from this which would result in column names like the following without writing them into the query:
Query result:
Singapore , Vancouver, Egypt, Tibet, ...
< values >
how can I produce a query which would result in column names like the
following without writing them into the query:
Even with crosstab() (from the tablefunc extension), you have to spell out the column names.
Except, if you create a dedicated C function for your query. The tablefunc extension provides a framework for this, output columns (the list of countries) have to be stable, though. I wrote up a "tutorial" for a similar case a few days ago:
PostgreSQL row to columns
The alternative is to use CASE statements like this:
SELECT sum(CASE WHEN t.id = 1 THEN o.ct END) AS "Singapore"
, sum(CASE WHEN t.id = 2 THEN o.ct END) AS "Vancouver"
, sum(CASE WHEN t.id = 3 THEN o.ct END) AS "Egypt"
-- more?
FROM tbl t
JOIN (
SELECT id, count(*) AS ct
FROM other_tbl
GROUP BY id
) o USING (id);
ELSE NULL is optional in a CASE expression. The manual:
If the ELSE clause is omitted and no condition is true, the result is null.
Basics for both techniques:
PostgreSQL Crosstab Query
You could do this with some really messing dynamic sql but I wouldn't recommend it.
However you could produce something like below, let me know if that stucture is acceptable and I will post some sql.
Location | Count
---------+------
Singapore| 1
Vancouver| 0
Egypt | 2
Tibet | 1
Crete | 3
Monaco | 0
Script for SelectTopNRows command from SSMS
drop table #yourtable;
create table #yourtable(id int, location varchar(25));
insert into #yourtable values
('1','Singapore'),
('2','Vancouver'),
('3','Egypt'),
('4','Tibet'),
('5','Crete'),
('6','Monaco');
drop table #temp;
create table #temp( col1 int );
Declare #Script as Varchar(8000);
Declare #Script_prepare as Varchar(8000);
Set #Script_prepare = 'Alter table #temp Add [?] varchar(100);'
Set #Script = ''
Select
#Script = #Script + Replace(#Script_prepare, '?', [location])
From
#yourtable
Where
[id] is not null
Exec (#Script);
ALTER TABLE #temp DROP COLUMN col1 ;
select * from #temp;
Related
I don't know how to union all tables with dynamic SQL.
The issue is that I'm inserting into db a number of tables - all having the same structure (only one varchar column
[Line]
). I don't know that would be the number of tables inserted - it depends on the project. But I want to automate the process in SQL.
I'm using this query to find those tables, additionally I'm adding some [RowNum] that may serve as an ID of each table:
SELECT
ROW_NUMBER() OVER (ORDER BY Name) AS [RowNum],
[Name] AS [Name]
INTO #all_tables_with_ids
FROM #all_tables
This query returns:
RowNum | Name
------------------------
1 | Table 1
2 | Table 2
3 | Table 3
4 | Table 4
I would like to merge all tables together. I was trying to write some insert into in while loop but it didn't work. I figured out that I need dynamic SQL.
Can you suggest something? I was trying to find some examples but all of them fail due to the fact that the list of tables is not known at the beginning, so it needs to be created dynamically as well.
Demo here:
create table #test
(
RowNum int,
Name varchar(100)
)
insert into #test
select 1,quotename('table1')
union all
select 2,quotename('table2')
declare #sql nvarchar(max)
set #sql='select somecol from tbl union all '
declare #sql1 nvarchar(max)
;with cte
as
(select #sql as ql,name,rplc
from
#test t1
cross apply
(select replace(#sql,'tbl',name) as rplc from #test t2 where t1.rownum=t2.rownum)b
)
select #sql1= stuff(
(select ''+rplc
from cte
for xml path('')
),1,0,'')
set #sql1=substring(#sql1,1,len(#sql1)-10)
print #sql1
--exec(#Sql1)
I'm doing a query which looks something like
SELECT id,name FROM table WHERE id IN (2,1,4,3)
I'd like to get
id name
2 B
1 A
4 D
3 C
but I'm getting
1 A
2 B
3 C
4 D
Is there any way to sort the query results in the same way as the list I'm including after IN?
Believe me, I have a practical reason that I would need it for ;)
SELECT id,name FROM table WHERE id IN (2,1,4,3)
ORDER BY CASE id
WHEN 2 THEN 1
WHEN 1 THEN 2
WHEN 4 THEN 3
WHEN 3 THEN 4
ELSE 5
END
This might solve your problem.
Solution 2, insert your list into a temp table and get them a running sequence
id, seq(+1 every new row added)
-----------------
2 1
1 2
4 3
3 4
then join 2 table together and order by this seq.
Okay, I did it myself. It's a bit mad but it works ;)
DECLARE #IDs varchar(max)
DECLARE #nr int
DECLARE #znak varchar(1)
DECLARE #index int
DECLARE #ID varchar(max)
SET #IDs='7002,7001,7004,7003'
SET #nr=1
SET #index=1
IF OBJECT_ID('tempdb..#temp') IS NOT NULL DROP TABLE #temp
CREATE TABLE #temp (nr int, id int)
--fill temp table with Ids
WHILE #index<=LEN(#Ids)
BEGIN
set #znak=''
set #ID=''
WHILE #znak<>',' AND #index<=LEN(#Ids)
BEGIN
SET #znak= SUBSTRING(#IDs,#index,1)
IF #znak<>',' SET #ID=#ID+#znak
SET #index=#index+1
END
INSERT INTO #temp(nr,id) VALUES (#nr,CAST(#ID as int))
SET #nr=#nr+1
END
-- select proper data in wanted order
SELECT MyTable.* FROM MyTable
INNER JOIN #temp ON MyTable.id=#temp.id
ORDER BY #temp.nr
Let's assume two tables:
TableA holds various data measurements from a variety of stations.
TableB holds metadata, about the columns used in TableA.
TableA has:
stationID int not null, pk
entryDate datetime not null, pk
waterTemp float null,
waterLevel float null ...etc
TableB has:
id int not null, pk, autoincrement
colname varchar(50),
unit varchar(50) ....etc
So for example, one line of data from tableA reads:
1 | 2013-01-01 00:00 | 2.4 | 3.5
two lines from tableB read:
1| waterTemp | celcius
2| waterLevel | meters
This is a simplified example. In truth, tableA might hold close to 20 different data columns, and table b has close to 10 metadata columns.
I am trying to design a view which will output the results like this:
StationID | entryDate | water temperature | water level |
1 | 2013-01-01 00:00 | 2.4 celcius | 3.5 meters |
So two questions:
Other than specifying subselects from TableB (..."where
colname='XXX'") for each column, which seems horribly insufficient
(not to mention...manual :P ), is there a way to get the result I
mentioned earlier with automatic match on colname?
I have a hunch
that this might be bad design on the database. Is it so? If yes,
what would be a more optimal design? (Bear in mind the complexity of
the data structure I mentioned earlier)
dynamic SQL with PIVOT is the answer. though it is dirty in terms of debugging or say for some new developer to understand the code but it will give you the result you expected.
check the below query.
in this we need to prepare two things dynamically. one is list columns in the result set and second is list of values will appear in PIVOT query. notice in the result i do not have NULL values for Column3, Column5 and Column6.
SET NOCOUNT ON
IF OBJECT_ID('TableA','u') IS NOT NULL
DROP TABLE TableA
GO
CREATE TABLE TableA
(
stationID int not null IDENTITY (1,1)
,entryDate datetime not null
,waterTemp float null
,waterLevel float NULL
,Column3 INT NULL
,Column4 BIGINT NULL
,Column5 FLOAT NULL
,Column6 FLOAT NULL
)
GO
IF OBJECT_ID('TableB','u') IS NOT NULL
DROP TABLE TableB
GO
CREATE TABLE TableB
(
id int not null IDENTITY(1,1)
,colname varchar(50) NOT NULL
,unit varchar(50) NOT NULL
)
INSERT INTO TableA( entryDate ,waterTemp ,waterLevel,Column4)
SELECT '2013-01-01',2.4,3.5,101
INSERT INTO TableB( colname, unit )
SELECT 'WaterTemp','celcius'
UNION ALL SELECT 'waterLevel','meters'
UNION ALL SELECT 'Column3','unit3'
UNION ALL SELECT 'Column4','unit4'
UNION ALL SELECT 'Column5','unit5'
UNION ALL SELECT 'Column6','unit6'
DECLARE #pvtInColumnList NVARCHAR(4000)=''
,#SelectColumnist NVARCHAR(4000)=''
, #SQL nvarchar(MAX)=''
----getting the list of Columnnames will be used in PIVOT query list
SELECT #pvtInColumnList = CASE WHEN #pvtInColumnList=N'' THEN N'' ELSE #pvtInColumnList + N',' END
+ N'['+ colname + N']'
FROM TableB
--PRINT #pvtInColumnList
----lt and rt are table aliases used in subsequent join.
SELECT #SelectColumnist= CASE WHEN #SelectColumnist = N'' THEN N'' ELSE #SelectColumnist + N',' END
+ N'CAST(lt.'+sc.name + N' AS Nvarchar(MAX)) + SPACE(2) + rt.' + sc.name + N' AS ' + sc.name
FROM sys.objects so
JOIN sys.columns sc
ON so.object_id=sc.object_id AND so.name='TableA' AND so.type='u'
JOIN TableB tbl
ON tbl.colname=sc.name
JOIN sys.types st
ON st.system_type_id=sc.system_type_id
ORDER BY sc.name
IF #SelectColumnist <> '' SET #SelectColumnist = N','+#SelectColumnist
--PRINT #SelectColumnist
----preparing the final SQL to be executed
SELECT #SQL = N'
SELECT
--this is a fixed column list
lt.stationID
,lt.entryDate
'
--dynamic column list
+ #SelectColumnist +N'
FROM TableA lt,
(
SELECT * FROM
(
SELECT colname,unit
FROM TableB
)p
PIVOT
( MAX(p.unit) FOR p.colname IN ( '+ #pvtInColumnList +N' ) )q
)rt
'
PRINT #SQL
EXECUTE sp_executesql #SQL
here is the result
ANSWER to your Second Question.
the design above is not even giving performance nor flexibility. if user wants to add new Metadata (Column and Unit) that can not be done w/o changing table definition of TableA.
if we are OK with writing Dynamic SQL to give user Flexibility we can redesign the TableA as below. there is nothing to change in TableB. I would convert it in to Key-value pair table. notice that StationID is not any more IDENTITY. instead for given StationID there will be N number of row where N is the number of column supplying the Values for that StationID. with this design, tomorrow if user adds new Column and Unit in TableB it will add just new Row in TableA. no table definition change required.
SET NOCOUNT ON
IF OBJECT_ID('TableA_New','u') IS NOT NULL
DROP TABLE TableA_New
GO
CREATE TABLE TableA_New
(
rowID INT NOT NULL IDENTITY (1,1)
,stationID int not null
,entryDate datetime not null
,ColumnID INT
,Columnvalue NVARCHAR(MAX)
)
GO
IF OBJECT_ID('TableB_New','u') IS NOT NULL
DROP TABLE TableB_New
GO
CREATE TABLE TableB_New
(
id int not null IDENTITY(1,1)
,colname varchar(50) NOT NULL
,unit varchar(50) NOT NULL
)
GO
INSERT INTO TableB_New(colname,unit)
SELECT 'WaterTemp','celcius'
UNION ALL SELECT 'waterLevel','meters'
UNION ALL SELECT 'Column3','unit3'
UNION ALL SELECT 'Column4','unit4'
UNION ALL SELECT 'Column5','unit5'
UNION ALL SELECT 'Column6','unit6'
INSERT INTO TableA_New (stationID,entrydate,ColumnID,Columnvalue)
SELECT 1,'2013-01-01',1,2.4
UNION ALL SELECT 1,'2013-01-01',2,3.5
UNION ALL SELECT 1,'2013-01-01',4,101
UNION ALL SELECT 2,'2012-01-01',1,3.6
UNION ALL SELECT 2,'2012-01-01',2,9.9
UNION ALL SELECT 2,'2012-01-01',4,104
SELECT * FROM TableA_New
SELECT * FROM TableB_New
SELECT *
FROM
(
SELECT lt.stationID,lt.entryDate,rt.Colname,lt.Columnvalue + SPACE(3) + rt.Unit AS ColValue
FROM TableA_New lt
JOIN TableB_new rt
ON lt.ColumnID=rt.ID
)t1
PIVOT
(MAX(ColValue) FOR Colname IN ([WaterTemp],[waterLevel],[Column1],[Column2],[Column4],[Column5],[Column6]))pvt
see the result below.
I would design this database like the following:
A table MEASUREMENT_DATAPOINT that contains the measured data points. It would have the columns ID, measurement_id, value, unit, name.
One entry would be 1, 1, 2.4, 'celcius', 'water temperature'.
A table MEASUREMENTS that contains the data of the measurement itself. Columns: ID, station_ID, entry_date.
You might want to look into the MS-SQL function called PIVOT/UNPIVOT
http://technet.microsoft.com/en-us/library/ms177410(v=sql.105).aspx
you can take column names and have them in rows or vice versa using this command.
Once you have the column name in the column itself you can join that column from tableA to tableB. Then unpivot to get your data back the way you want it. (caveat I may be swapping the use of pivot and unpivot :))
Word to the wise though, if you are working with large tables, pivot is not the fastest of operations.
I think you would have to flip it to a row per metric. Looking at your design above:
1 | 2013-01-01 00:00 | 2.4 | 3.5
How do I know what row in table b that applies to?
I would try something like this:
Table B:
Metric_Key | Metric
1 | WaterLevel in Meters
2 | Temp in Celcius
...
Table A:
StationID | entrydate | Metric_Key | Value
1 2013-01-01 00:00 1 2.4
every updated record must have different value by using a procedure
the procedure returns single integer value
declare #value int;
exec #value = get_proc param;
update table1 set field1 = #value;
this will work for one record but i want the procedure to get new value for each record
Just a quick example of how to use a TVF to perform this type of update:
USE tempdb;
GO
CREATE TABLE dbo.Table1(ID INT, Column1 INT);
INSERT dbo.Table1(ID)
SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3;
GO
CREATE FUNCTION dbo.CalculateNewValue
(#ID INT)
RETURNS TABLE
AS
-- no idea what this logic would be,
-- just showing an example
RETURN(SELECT NewValue = #ID + 1);
GO
SELECT t1.ID, n.NewValue
FROM dbo.Table1 AS t1
CROSS APPLY dbo.CalculateNewValue(t1.ID) AS n;
Results:
ID NewValue
-- --------
1 2
2 3
3 4
Now an update that uses the same information:
UPDATE t1 SET Column1 = n.NewValue
FROM dbo.Table1 AS t1
CROSS APPLY dbo.CalculateNewValue(t1.ID) AS n;
SELECT ID, Column1 FROM dbo.Table1;
Results:
ID Column1
-- -------
1 2
2 3
3 4
Does it really need to be a procedure ? If you can implement get_proc as function, then you can apply it on every record that you want ;)
Also, what are you using value1 for ? In the example that you've provided, it's not needed.
Is there any way to group by all the columns of a table without specifying the column names? Like:
select * from table group by *
The DISTINCT Keyword
I believe what you are trying to do is:
SELECT DISTINCT * FROM MyFooTable;
If you group by all columns, you are just requesting that duplicate data be removed.
For example a table with the following data:
id | value
----+----------------
1 | foo
2 | bar
1 | foo
3 | something else
If you perform the following query which is essentially the same as SELECT * FROM MyFooTable GROUP BY * if you are assuming * means all columns:
SELECT * FROM MyFooTable GROUP BY id, value;
id | value
----+----------------
1 | foo
3 | something else
2 | bar
It removes all duplicate values, which essentially makes it semantically identical to using the DISTINCT keyword with the exception of the ordering of results. For example:
SELECT DISTINCT * FROM MyFooTable;
id | value
----+----------------
1 | foo
2 | bar
3 | something else
If you are using SqlServer the distinct keyword should work for you. (Not sure about other databases)
declare #t table (a int , b int)
insert into #t (a,b) select 1, 1
insert into #t (a,b) select 1, 2
insert into #t (a,b) select 1, 1
select distinct * from #t
results in
a b
1 1
1 2
I wanted to do counts and sums over full resultset. I achieved grouping by all with GROUP BY 1=1.
Short answer: no. GROUP BY clauses intrinsically require order to the way they arrange your results. A different order of field groupings would lead to different results.
Specifying a wildcard would leave the statement open to interpretation and unpredictable behaviour.
nope. are you trying to do some aggregation? if so, you could do something like this to get what you need
;with a as
(
select sum(IntField) as Total
from Table
group by CharField
)
select *, a.Total
from Table t
inner join a
on t.Field=a.Field
No because this fundamentally means that you will not be grouping anything. If you group by all columns (and have a properly defined table w/ a unique index) then SELECT * FROM table is essentially the same thing as SELECT * FROM table GROUP BY *.
Here is my suggestion:
DECLARE #FIELDS VARCHAR(MAX), #NUM INT
--DROP TABLE #FIELD_LIST
SET #NUM = 1
SET #FIELDS = ''
SELECT
'SEQ' = IDENTITY(int,1,1) ,
COLUMN_NAME
INTO #FIELD_LIST
FROM Req.INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = N'new340B'
WHILE #NUM <= (SELECT COUNT(*) FROM #FIELD_LIST)
BEGIN
SET #FIELDS = #FIELDS + ',' + (SELECT COLUMN_NAME FROM #FIELD_LIST WHERE SEQ = #NUM)
SET #NUM = #NUM + 1
END
SET #FIELDS = RIGHT(#FIELDS,LEN(#FIELDS)-1)
EXEC('SELECT ' + #FIELDS + ', COUNT(*) AS QTY FROM [Req].[dbo].[new340B] GROUP BY ' + #FIELDS + ' HAVING COUNT(*) > 1 ')
You can use Group by All but be careful as Group by All will be removed from future versions of SQL server.