Hello Am trying my query as belo.
Please see the two different versions of query and its error message.
SELECT first_value(col1) AS 'inv',col2
FROM dbo.table
--first_value' is not a recognized built-in function name.
SELECT dbo.first_value(col1) AS 'inv',col2
FROM dbo.table
--Cannot find either column "dbo" or the user-defined function or aggregate "dbo.first", or the name is ambiguous.
SELECT first_value(col1) AS 'inv',col2
FROM dbo.table
GROUP BY col2
--'first' is not a recognized built-in function name.
SELECT dbo.first_value(col1) AS 'inv',col2
FROM dbo.table
GROUP BY col2
--Cannot find either column "dbo" or the user-defined function or aggregate "dbo.first", or the name is ambiguous.
Please any help!
If you are trying to pull the top / first record from a table, you need to specify the criteria by which a row is defined as the first / top row
SELECT top 1 col1 AS inv,col2
FROM dbo.table
ORDER BY col1 --or whatever criteria you need here
first_value as far as I can tell seems to be a MS SQL Server 2012 function, which also requires an ordering clause - http://msdn.microsoft.com/en-us/library/hh213018.aspx
Related
I have this SQL query:
select top(1)
salary
from
(select top(2) salary
from employee
order by salary desc) as b
order by
salary asc
If I don't utilize as b it will give me an error:
Incorrect syntax near ...
Why is mandatory to use as in this query?
You don't need the as keyword. In fact, I advise using as for column aliases but not for table aliases. So, I would write this as:
select top(1) salary
from (select top(2) salary
from employee
order by salary desc
) b
order by salary asc;
You do need the table alias for the subquery, because SQL Server requires that all subqueries in the from clause be named.
This is TSql syntax. Subquery in FROM must have an alias even it's never used. Oracle for example considers this alias optional.
This is because you have a sub-query that, according to the Transact-SQL documentation on FROM, makes the use of an alias mandatory:
When a derived table, rowset or table-valued function, or operator clause (such as PIVOT or UNPIVOT) is used, the required table_alias at the end of the clause is the associated table name for all columns, including grouping columns, returned.
Note that with derived table the kind of sub-query is intended that you use in your SQL statement:
derived_table
Is a subquery that retrieves rows from the database. derived_table is used as input to the outer query.
Because you are using 'salary' twice. Without an alias the interpreter won't know what 'salary' to order the results by. By using an alias it can discern between employee.salary and b.salary.
A different approach to get the 2nd highest salary... as if you need the 3rd or 4th you're approach would get much more challenging...
SELECT *
FROM (SELECT salary, row_number() over (order by salary desc) rn
FROM employee) E
WHERE rn = 2
You are creating two queries. The first one selects the top 2 salaries from employee. You are calling this list "b". Then you are selecting the top salary from "b".
Can someone explain to me why this is possible with SQL Server :
select column1 c,column2 d
from table1
order by c,column3
I can sort by column1 using the alias because order by clause is applied after the select clause, but how is it possible to sort by a column that i'm not retreiving ?
Thanks in advance.
All column names from the objects in the FROM clause are available to ORDER BY, except in the case of GROUPing or DISTINCT. As you've indicated the alias is also available, because the SELECT statement is processed before the ORDER BY.
This is one of those cases where you trust the optimizer.
According to Books Online (http://technet.microsoft.com/en-us/library/ms188385(v=sql.90).aspx)
The ORDER BY clause can include items that do not appear in the
select list. However, if SELECT DISTINCT is specified, or if the
statement contains a GROUP BY clause, or if the SELECT statement
contains a UNION operator, the sort columns must appear in the select
list.
Additionally, when the SELECT statement includes a UNION operator, the
column names or column aliases must be those specified in the first
select list.
You can sort by alias' which you define in the select select column1 c and then you tell it to sort by a column that you are not including in the select, but one that still exists in the table. This allows us to sort by expressions of data, without having to have it in the select.
Select cost, tax From table ORDER BY (cost*tax)
I have searched for paging in SQL Server. I found most of the solution look like that
What is the best way to paginate results in SQL Server
But it don't meet my expectation.
Here is my situation:
I work on JasperReport, for that: to export the report I just need pass the any Select query into the template, it will auto generated out the report
EX : I have a select query like this:
Select * from table A
I don't know any column names in table A. So I can't use
Select ROW_NUMBER() Over (Order By columsName)
And I also don't want it order by any columns.
Anyone can help me do it?
PS: In Oracle , it have rownum very helpful in this case.
Select * from tableA where rownum > 100 and rownum <200
Paging with Oracle
You should use ROW_NUMBER with an ORDER BY - because without an ORDER BY there is no determinism in how rows are returned. You can run the same query three times and get the results back in three different orders. Especially if merry-go-round scans come into play.
So unless you want your report to have the possibility of showing the same rows to users on multiple pages, or some rows never on any page, you need to find a way to order the result set to make it deterministic.
From my opinion, you can use sql query to find out how many columns in a table, and then find out a proper one for ' order by ' to depend on.
The script of how to get out columns of an table refer to : How can I get column names from a table in SQL Server?
Check out this link
http://msdn.microsoft.com/en-us/library/ms186734.aspx
SQL Server has similar function ROW_NUMBER. Though it behaves a bit differently.
SQL Server provides no guarantee of row order unless you have have specified a column in order by clause. I would recommend that you give an order by clause that has unique values.
Thank for all your help. Because of order by are required when paging in MS SQL Server, so I used ResultSetMetaData to get the Columns name and do paging as well.
You can use the below query aswell.
declare #test table(
id int,
value1 varchar(100),
value2 int)
insert into #test values(1,'10/50',50)
insert into #test values(2,'10/60',60)
insert into #test values(3,'10/60',61)
insert into #test values(4,'10/60',10)
insert into #test values(5,'10/60',11)
insert into #test values(6,'10/60',09)
select *
from ( select row_number() over (order by (select 0)) as rownumber,* from #test )test
where test.rownumber<=5
Using SQL Server Management Studio, I am getting some undesired results (looks like a bug to me..?)
If I use (FIELD rather than field for the other_table):
SELECT * FROM main_table WHERE field IN (SELECT FIELD FROM other_table)
I get all results from main_table.
Using the correct case:
SELECT * FROM main_table WHERE field IN (SELECT field FROM other_table)
I get the expected results where field appears in other.
Running the subquery on it's own:
SELECT FIELD FROM other_table
I get an invalid column name error.
Surely I should get this error in the first case?
Is this related to collation?
The DB is binary collation.
The server is case insensitive however.
It seems to me like the server component is saying "this code is OK" and not allowing the DB to say the field is the wrong name..?
What are my options for a solution?
Let's illustrate what is happening using something that doesn't depend on case sensitivity:
USE tempdb;
GO
CREATE TABLE dbo.main_table(column1 INT);
CREATE TABLE dbo.other_table(column2 INT);
INSERT dbo.main_table SELECT 1 UNION ALL SELECT 2;
INSERT dbo.other_table SELECT 1 UNION ALL SELECT 3;
SELECT column1 FROM dbo.main_table
WHERE column1 IN (SELECT column1 FROM dbo.other_table);
Results:
column1
-------
1
2
Why doesn't that raise an error? SQL Server is looking at your queries and seeing that the column1 inside can't possibly be in other_table, so it is extrapolating and "using" the column1 that exists in the outer referenced table (just like you could reference a column that only exists in the outer table without a table reference). Think about this variation:
SELECT [column1] FROM dbo.main_table
WHERE EXISTS (SELECT [column1] FROM dbo.other_table WHERE [column2] = [column1]);
Results:
column1
-------
1
Again SQL Server knows that column1 in the where clause also doesn't exist in the locally referenced table, but it tries to find it in the outer scope. So in an imaginary world you might consider the query to actually be saying:
SELECT m.[column1] FROM dbo.main_table AS m
WHERE EXISTS (SELECT m.[column1] FROM dbo.other_table AS o WHERE o.[column2] = m.[column1]);
(Which is not how I typed it, but if I do type it that way, it still works.)
It doesn't make logical sense in some of the cases but this is the way the query engine does it and the rule has to be applied consistently. In your case (no pun intended), you have an extra complication: case sensitivity. SQL Server didn't find FIELD in your subquery, but it did find it in the outer query. So a couple of lessons:
Always prefix your column references with the table name or alias (and always prefix your table references with the schema).
Always create and reference your tables, columns and other entities using consistent case. Especially when using a binary or case-sensitive collation.
Very interesting find. The unspoken mandate is that you always should alias tables in your subqueries and use those aliases to be explicit about which table your column comes from. Subqueries allow you to make reference to a field from your outer query which is the cause of your issue, but in your scenario I would agree that either the default should be the internal query's field list, or to give you a column ambiguity error. Regardless, this method below is always preferable:
select * from main_table a where a.field in
(select x.field from other_table x)
Can I use my table valued function in order by clause of my select query????
Like this :
declare #ID int
set #ID=9011
Exec ('select top 10 * from cs_posts order by ' + (select * from dbo.gettopposter(#ID)) desc)
GetTopPoster(ID) is my table valued function.
Please help me on this.
You can use a table-valued function with a join. That also allows you to choose any combination of columns to sort by:
select top 10 *
from cs_posts p
join dbo.gettopposter(#ID) as gtp
on p.poster_id = gtp.poster_id
order by
gtp.col1
, gtp.col2
Yes. You can use a Table Valued Function just as a normal table.
Your query is not valid SQL though, despite the TVF.
For further reference:
http://msdn.microsoft.com/en-us/library/ms191165.aspx
You can't do it like that - how does it know what to order by? It doesn't know how the TVF relates to the original query. You can join the two however (as I assume cs_posts has an id column which relates to the TVF) and then order by the the TVF id column.