If I try to execute the following code, I get the errors
Msg 207, Level 16, State 1, Line 3 Invalid column name 'Another'. Msg
207, Level 16, State 1, Line 4 Invalid column name 'Another'.
even though the predicate for both IF statements always evaluates to false.
CREATE TABLE #Foo (Bar INT)
GO
IF (1=0)
BEGIN
SELECT Another FROM #Foo
END
GO
IF (1=0)
BEGIN
ALTER TABLE #Foo ADD Another INT
SELECT Another FROM #Foo
END
GO
DROP TABLE #Foo
This is probably over-simplified for the sake of the example; in reality what I need to do is select the values from a column, but only if the column exists. If it doesn't exist, I don't care about it. In the problem that drove me to ask this question, my predicate was along the lines of EXISTS (SELECT * FROM sys.columns WHERE object_id = #ID AND name = #Name). Is there a way to achieve this without resorting to my arch-enemy Dynamic SQL? I understand that my SQL must always be well-formed (i.e. conform to grammar) - even within a block that's never executed - but I'm flabbergasted that I'm also being forced to make it semantically correct too!
EDIT:
Though I'm not sure the code below adds much to the code above, it's a further example of the problem. In this scenario, I only want to set the value of Definitely (which definitely exists as a column) with the value from Maybe (which maybe exists as a column) if Maybe exists.
IF EXISTS (SELECT * FROM sys.columns WHERE object_id = OBJECT_ID('dbo.TableName', 'U') AND name = 'Maybe')
BEGIN
UPDATE dbo.TableName SET Definitely = Maybe
END
SQL Server doesn't execute line by line. It isn't procedural like .net or Java code. So there is no "non-executed block"
The batch is compiled in one go. At this point, the column doesn't exist but it knows the table will be. Table does not have a column called "Another". Fail.
Exactly as expected.
Now, what is the real problem you are trying to solve?
Some options:
2 tables or one table with both columns
use Stored procedures to decouple scope
not use temp tables (maybe not needed; it could be your procedural thinking...)
dynamic SQL (from Mitch's deleted answer)
Edit, after comment;
Why not hide schema changes behind a view, rather than changing all code to work with columns that may/may not be there?
You can use EXEC to handle it. It's not really dynamic SQL if the code never actually changes.
For example:
CREATE TABLE dbo.Test (definitely INT NOT NULL)
INSERT INTO dbo.Test (definitely) VALUES (1), (2), (3)
IF EXISTS (SELECT *
FROM sys.columns
WHERE object_id = OBJECT_ID('dbo.Test', 'U') AND
name = 'Maybe')
BEGIN
EXEC('UPDATE dbo.Test SET definitely = maybe')
END
SELECT * FROM dbo.Test
ALTER TABLE dbo.Test ADD maybe INT NOT NULL DEFAULT 999
IF EXISTS (SELECT *
FROM sys.columns
WHERE object_id = OBJECT_ID('dbo.Test', 'U') AND
name = 'Maybe')
BEGIN
EXEC('UPDATE dbo.Test SET definitely = maybe')
END
SELECT * FROM dbo.Test
DROP TABLE dbo.Test
You can also try Martin Smith's "Workaround" using a non-existing table to get "deferred name resolution" for columns.
I had the same issue.
We are creating a script for all changes for years and this is the first time that we have this issue.
I've tried all your answers and didn't find the issue.
In my case it was because of temporary table within the script that I'm using also within a stored procedure, although every sentence has go.
I've found that if I'm adding if exists with drop to the temporary table after the script is using the temporary table, it is working correctly.
Best regards,
Chen
Derived from the answer by #gbn.
What i did to solve the issue was to use 'GO' between the ALTER query and the query that uses the column added by ALTER. This will make the 2 queries to be run as separate batches thereby ensuring your 'Another' column is there before the SELECT query.
Related
I am having problems with some of my SQL scripts on SQL SERVER, indeed I am trying to transfer data from a column A to a column B of the same table and then drop the column B,
However my problem is that I have to check for the existence of A beforehand because the code is meant to be executed on a server where I don't have access (I work as a third party developper on a professionnal app)
Here is my code:
-- Export the data from the column name
-- Drop the column name
USE p_mynacellelocation_db_ChecklistWPF
GO
IF COL_LENGTH('model_trolley_part','name') IS NOT NULL
BEGIN
UPDATE model_trolley_part
SET name_en=[name];
ALTER TABLE model_trolley_part
DROP COLUMN [name];
END
In the case of the column name being non existent I would like not to do anything
However on execution of the code in a database where the column name is non existent SQL Server returns me:
Msg 207, Level 16, State 1, Line 12 Invalid column name 'name'.
Instead of jumping through all these hoops simply rename your original column.
https://learn.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-rename-transact-sql?view=sql-server-2017
exec sp_rename 'model_trolley_part.name', 'name_en', 'COLUMN'
You need to use dynamic SQL for this. The reason is that the parser will try to validate your code, even the code that won't be executed because its IF condition wouldn't be met.
The parser is smart enough to see there is no table named name, but it's not smart enough to realize that the code shouldn't get executed because of the IF, so it raises a parsing error.
Using dynamic SQL in the BEGIN..END block after the IF hides this from the parser so it will execute.
Try this:
IF EXISTS(SELECT *
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'myTableName'
AND COLUMN_NAME = 'ColumnA')
BEGIN
// your update and drop code goes here
END
you might want to check your account privileges if you are modifying table structure etc..
In my Stored procedure, I have added a command to create a hash temp table #DIR_CAT. But every time I execute the procedure I get this error:
"There is already an object named '#DIR_Cat' in the database."
Even when I have already created an Exists clause at the start of SP to check and drop the table if it is present. Any help is much appreciated.
The code goes like this.
if exists (select * from dbo.sysobjects where id = object_id(N'#DIR_Cat') )
drop table #DIR_Cat
/* some lines of code*/
CREATE TABLE #DIR_Cat (XMLDta xml)
/* some lines of code*/
INSERT #DIR_Cat exec (#stmt)
/* some lines of code*/
drop table #DIR_Cat
Main issue is you're not fully qualifying your objects. Your temp table lives in tempdb, whereas the system views use whatever database you're currently connected to by default. So essentially you're looking for the temp table, but you're looking in whatever database your currently connected to (which I'm guessing is not tempdb).
I'm assuming you're using SQL Server here, although you did also mention mysql in the tags. If that's what you're using, this code may not apply.
Here's the snippet I use for temp table drop/create
if object_id('tempdb.dbo.#<TableName, sysname, >') is not null drop table #<TableName, sysname, >
create table #<TableName, sysname, >
(
)
Side note, don't use dbo.sysobjects. That's a really old compatibility view. If you want to use objects, use sys.objects instead.
temp table does not exists in local DB sys.objects, it is in tempdb
you need to query tempb.sys.objects
the name of the temp table does not appear exactly as it is in the tempdb.sys.objects.
You can't query it just like
select *
from tempdb.sys.objects
where name = '#DIR_Cat' -- This does not works
you need to use object_id()
select *
from tempdb.sys.objects
where object_id = object_id('tempdb..#DIR_Cat')
I have a a number of sp's that create a temporary table #TempData with various fields. Within these sp's I call some processing sp that operates on #TempData. Temp data processing depends on sp input parameters. SP code is:
CREATE PROCEDURE [dbo].[tempdata_proc]
#ID int,
#NeedAvg tinyint = 0
AS
BEGIN
SET NOCOUNT ON;
if #NeedAvg = 1
Update #TempData set AvgValue = 1
Update #TempData set Value = -1;
END
Then, this sp is called in outer sp with the following code:
USE [BN]
--GO
--DBCC FREEPROCCACHE;
GO
Create table #TempData
(
tele_time datetime
, Value float
--, AvgValue float
)
Create clustered index IXTemp on #TempData(tele_time);
insert into #TempData(tele_time, Value ) values( GETDATE(), 50 ); --sample data
declare
#ID int,
#UpdAvg int;
select
#ID = 1000,
#UpdAvg = 1
;
Exec dbo.tempdata_proc #ID, #UpdAvg ;
select * from #TempData;
drop table #TempData
This code throws an error: Msg 207, Level 16, State 1, Procedure tempdata_proc, Line 8: Invalid column name "AvgValue".
But if only I uncomment declaration AvgValue float - everything works OK.
The question: is there any workaround letting the stored proc code remain the same and providing a tip to the optimizer - skip this because AvgValue column will not be used by the sp due to params passed.
Dynamic SQL is not a welcomed solution BTW. Using alternative to #TempData tablename is undesireable solution according to existing tsql code (huge modifications necessary for that).
Tried SET FMTONLY, tempdb.tempdb.sys.columns, try-catch wrapping without any success.
The way that stored procedures are processed is split into two parts - one part, checking for syntactical correctness, is performed at the time that the stored procedure is created or altered. The remaining part of compilation is deferred until the point in time at which the store procedure is executed. This is referred to as Deferred Name Resolution and allows a stored procedure to include references to tables (not just limited to temp tables) that do not exist at the point in time that the procedure is created.
Unfortunately, when it comes to the point in time that the procedure is executed, it needs to be able to compile all of the individual statements, and it's at this time that it will discover that the table exists but that the column doesn't - and so at this time, it will generate an error and refuse to run the procedure.
The T-SQL language is unfortunately a very simplistic compiler, and doesn't take runtime control flow into account when attempting to perform the compilation. It doesn't analyse the control flow or attempt to defer the compilation in conditional paths - it just fails the compilation because the column doesn't (at this time) exist.
Unfortunately, there aren't any mechanisms built in to SQL Server to control this behaviour - this is the behaviour you get, and anything that addresses it is going to be perceived as a workaround - as evidenced already by the (valid) suggestions in the comments - the two main ways to deal with it are to use dynamic SQL or to ensure that the temp table always contains all columns required.
One way to workaround your concerns about maintenance if you go down the "all uses of the temp table should have all columns" is to move the column definitions into a separate stored procedure, that can then augment the temporary table with all of the required columns - something like:
create procedure S_TT_Init
as
alter table #TT add Column1 int not null
alter table #TT add Column2 varchar(9) null
go
create procedure S_TT_Consumer
as
insert into #TT(Column1,Column2) values (9,'abc')
go
create procedure S_TT_User
as
create table #TT (tmp int null)
exec S_TT_Init
insert into #TT(Column1) values (8)
exec S_TT_Consumer
select Column1 from #TT
go
exec S_TT_User
Which produces the output 8 and 9. You'd put your temp table definition in S_TT_Init, S_TT_Consumer is the inner query that multiple stored procedures call, and S_TT_User is an example of one such stored procedure.
Create the table with the column initially. If you're populating the TEMP table with SPROC output just make it an IDENTITY INT (1,1) so the columns line up with your output.
Then drop the column and re-add it as the appropriate data type later on in the SPROC.
The only (or maybe best) way i can thing off beyond dynamic SQL is using checks for database structure.
if exists (Select 1 From tempdb.sys.columns Where object_id=OBJECT_ID('tempdb.dbo.#TTT') and name = 'AvgValue')
begin
--do something AvgValue related
end
maybe create a simple function that takes table name and column or only column if its always #TempTable and retursn 1/0 if the column exists, would be useful in the long run i think
if dbo.TempTableHasField('AvgValue')=1
begin
-- do something AvgValue related
end
EDIT1: Dang, you are right, sorry about that, i was sure i had ... this.... :( let me thing a bit more
Brief history:
I'm writing a stored procedure to support a legacy reporting system (using SQL Server Reporting Services 2000) on a legacy web application.
In keeping with the original implementation style, each report has a dedicated stored procedure in the database that performs all the querying necessary to return a "final" dataset that can be rendered simply by the report server.
Due to the business requirements of this report, the returned dataset has an unknown number of columns (it depends on the user who executes the report, but may have 4-30 columns).
Throughout the stored procedure, I keep a column UserID to track the user's ID to perform additional querying. At the end, however, I do something like this:
UPDATE #result
SET Name = ppl.LastName + ', ' + ppl.FirstName
FROM #result r
LEFT JOIN Users u ON u.id = r.userID
LEFT JOIN People ppl ON ppl.id = u.PersonID
ALTER TABLE #result
DROP COLUMN [UserID]
SELECT * FROM #result r ORDER BY Name
Effectively I set the Name varchar column (that was previously left NULL while I was performing some pivot logic) to the desired name format in plain text.
When finished, I want to drop the UserID column as the report user shouldn't see this.
Finally, the data set returned has one column for the username, and an arbitrary number of INT columns with performance totals. For this reason, I can't simply exclude the UserID column since SQL doesn't support "SELECT * EXCEPT [UserID]" or the like.
With this known (any style pointers are appreciated but not central to this problem), here's the problem:
When I execute this stored procedure, I get an execution error:
Invalid column name 'userID'.
However, if I comment out my DROP COLUMN statement and retain the UserID, the stored procedure performs correctly.
What's going on? It certainly looks like the statements are executing out of order and it's dropping the column before I can use it to set the name strings!
[Edit 1]
I defined UserID previously (the whole stored procedure is about 200 lies of mostly irrelevant logic, so I'll paste snippets:
CREATE TABLE #result ([Name] NVARCHAR(256), [UserID] INT);
Case sensitivity isn't the problem but did point me to the right line - there was one place in which I had userID instead of UserID. Now that I fixed the case, the error message complains about UserID.
My "broken" stored procedure also works properly in SQL Server 2008 - this is either a 2000 bug or I'm severely misunderstanding how SQL Server used to work.
Thanks everyone for chiming in!
For anyone searching this in the future, I've added an extremely crude workaround to be 2000-compatible until we update our production version:
DECLARE #workaroundTableName NVARCHAR(256), #workaroundQuery NVARCHAR(2000)
SET #workaroundQuery = 'SELECT [Name]';
DECLARE cur_workaround CURSOR FOR
SELECT COLUMN_NAME FROM [tempdb].INFORMATION_SCHEMA.Columns WHERE TABLE_NAME LIKE '#result%' AND COLUMN_NAME <> 'UserID'
OPEN cur_workaround;
FETCH NEXT FROM cur_workaround INTO #workaroundTableName
WHILE ##FETCH_STATUS = 0
BEGIN
SET #workaroundQuery = #workaroundQuery + ',[' + #workaroundTableName + ']'
FETCH NEXT FROM cur_workaround INTO #workaroundTableName
END
CLOSE cur_workaround;
DEALLOCATE cur_workaround;
SET #workaroundQuery = #workaroundQuery + ' FROM #result ORDER BY Name ASC'
EXEC(#workaroundQuery);
Thanks everyone!
A much easier solution would be to not drop the column, but don't return it in the final select.
There are all sorts of reasons why you shouldn't be returning select * from your procedure anyway.
EDIT: I see now that you have to do it this way because of an unknown number of columns.
Based on the error message, is the database case sensitive, and so there's a difference between userID and UserID?
This works for me:
CREATE TABLE #temp_t
(
myInt int,
myUser varchar(100)
)
INSERT INTO #temp_t(myInt, myUser) VALUES(1, 'Jon1')
INSERT INTO #temp_t(myInt, myUser) VALUES(2, 'Jon2')
INSERT INTO #temp_t(myInt, myUser) VALUES(3, 'Jon3')
INSERT INTO #temp_t(myInt, myUser) VALUES(4, 'Jon4')
ALTER TABLE #temp_t
DROP Column myUser
SELECT * FROM #temp_t
DROP TABLE #temp_t
It says invalid column for you. Did you check the spelling and ensure there even exists that column in your temp table.
You might try wrapping everything preceding the DROP COLUMN in a BEGIN...COMMIT transaction.
At compile time, SQL Server is probably expanding the * into the full list of columns. Thus, at run time, SQL Server executes "SELECT UserID, Name, LastName, FirstName, ..." instead of "SELECT *". Dynamically assembling the final SELECT into a string and then EXECing it at the end of the stored procedure may be the way to go.
I'm after a simple stored procedure to drop tables. Here's my first attempt:
CREATE PROC bsp_susf_DeleteTable (#TableName char)
AS
IF EXISTS (SELECT name FROM sysobjects WHERE name = #TableName)
BEGIN
DROP TABLE #TableName
END
When I parse this in MS Query Analyser I get the following error:
Server: Msg 170, Level 15, State 1, Procedure bsp_susf_DeleteTable, Line 6
Line 6: Incorrect syntax near '#TableName'.
Which kind of makes sense because the normal SQL for a single table would be:
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'tbl_XYZ')
BEGIN
DROP TABLE tbl_XYZ
END
Note the first instance of tbl_XYZ (in the WHERE clause) has single quotes around it, while the second instance in the DROP statement does not. If I use a variable (#TableName) then I don't get to make this distinction.
So can a stored procedure be created to do this? Or do I have to copy the IF EXISTS ... everywhere?
You should be able to use dynamic sql:
declare #sql varchar(max)
if exists (select name from sysobjects where name = #TableName)
BEGIN
set #sql = 'drop table ' + #TableName
exec(#sql)
END
Hope this helps.
Update: Yes, you could make #sql smaller, this was just a quick example. Also note other comments about SQL Injection Attacks
Personally I would be very wary of doing this. If you feel you need it for administrative purposes, please make sure the rights to execute this are extremely limited. Further, I would have the proc copy the table name and the date and the user executing it to a logging table. That way at least you will know who dropped the wrong table. You may want other protections as well. For instance you may want to specify certain tables that cannot be dropped ever using this proc.
Further this will not work on all tables in all cases. You cannot drop a table that has a foreign key associated with it.
Under no circumstances would I allow a user or anyone not the database admin to execute this proc. If you havea a system design where users can drop tables, there is most likely something drastically wrong with your design and it should be rethought.
Also, do not use this proc unless you have a really, really good backup schedule in place and experience restoring from backups.
You'll have to use EXEC to execute that query as a string. In other words, when you pass in the table name, define a varchar and assign the query and tablename, then exec the variable you created.
Edit: HOWEVER, I don't recommend that because someone could pass in sql rather than a TableName and cause all kinds of wonderful problems. See Sql injection for more information.
Your best bet is to create a parameterized query on the client side for this. For example, in C# I would do something like:
// EDIT 2: on second thought, ignore this code; it probably won't work
SqlCommand sc = new SqlCommand();
sc.Connection = someConnection;
sc.CommandType = Command.Text;
sc.CommandText = "drop table #tablename";
sc.Parameters.AddWithValue("#tablename", "the_table_name");
sc.ExecuteNonQuery();