I'm trying to make sure that when people create tables it starts with the prefix tbl
Here is what I did as of now:
CREATE TRIGGER trg_tbl ON DATABASE
FOR CREATE_TABLE
AS
DECLARE #name VARCHAR(25)
SET #name = (SELECT TOP 1 name
FROM sys.tables
ORDER BY create_date DESC)
IF (SELECT SUBSTRING(#name, 1, 3) != 'tbl'
PRINT 'Tables must begin with the prefix tbl'
ROLLBACK
GO
The problem is it doesn't let me use != operator. I tried using = <> or LIKE but nothing seems to work it keeps telling me that the syntax is incorrect please help I looked everywhere online and everybody says that = or LIKE work. :(
Though the other answer explain the issue in your code. I will suggest you to use Eventdata() function to retrieve table name
Also your DDL trigger will rollback every Create Table action even though the table name starts with tb1. You need to apply rollback only when table name not starts with tb1 move the rollback command inside the IF condition.
Use BEGIN-END block when IF condition has more than one statement else the first statement alone will considered inside the IF condition.
CREATE TRIGGER trg_tbl
ON DATABASE
FOR CREATE_TABLE
AS
BEGIN
SET NOCOUNT ON
DECLARE #TABLE_NAME SYSNAME
SELECT #TABLE_NAME = Eventdata().value('(/EVENT_INSTANCE/ObjectName)[1]', 'SYSNAME')
IF LEFT (#TABLE_NAME, 3) != 'tbl'
BEGIN
PRINT 'Tables must begin with the prefix tbl'
ROLLBACK
END
END
GO
Error is because of a missing closing bracket at:
IF (SELECT SUBSTRING(#name,1,3) != 'tbl'
can be fixed by adding the missing closing bracket:
IF (SELECT SUBSTRING(#name,1,3)) != 'tbl'
However, you don't need to do a select to perform substring.
You can do this:
IF SUBSTRING(#name,1,3) != 'tbl'
Related
I am running the following query:
SELECT * INTO dbo.2015_10_2_cs FROM dbo.2015_10_2
IF NOT EXISTS
(SELECT type FROM sys.indexes WHERE object_id = object_id('dbo.2015_10_2_cs')
AND NAME ='cci' AND type = 5)
BEGIN
CREATE CLUSTERED COLUMNSTORE INDEX cci
ON dbo.2015_10_2_cs
DROP TABLE dbo.2015_10_2
EXEC sp_rename "dbo.2015_10_2_cs" , "dbo.2015_10_2"
END
and I want to make sure that the part where I am renaming the table dbo.2015_10_2_cs to dbo.2015_10_2 is done successfully (without losing any data).
The step inside the loop should be surrounded with SQL transaction to keep the process safe and reliable (in case if any step will fail).
Could anyone help with this? Thanks in advance.
EXEC sp_rename "dbo.2015_10_2_cs" , "dbo.2015_10_2"
This will not do what you expect. The new table will be named [dbo].[dbo.2015_10_2] if you specify the schema name in the new table name. Renamed tables are implicitly in the existing table's schema since one must use ALTER SCHEMA instead of sp_rename to move an object between schemas.
There are a number of other problems with your script. Because the table name starts with a number, it doesn't conform to regular identifier naming rules and must be enclosed in square brackets or double quotes. The literal parameters passed to sp_rename should be single quotes. You can also check to stored procedure return code to ascertain success or failure. The example below performs these tasks in a transaction with structured error handling.
DECLARE #rc int;
BEGIN TRY
BEGIN TRAN;
IF NOT EXISTS
(SELECT type FROM sys.indexes WHERE object_id = object_id(N'dbo.2015_10_2_cs')
AND NAME ='cci' AND type = 5)
BEGIN
CREATE CLUSTERED COLUMNSTORE INDEX cci
ON dbo.[2015_10_2_cs];
DROP TABLE dbo.[2015_10_2];
EXEC #rc = sp_rename 'dbo.[2015_10_2_cs]' , '2015_10_2';
IF #rc <> 0
BEGIN
RAISERROR('sp_rename returned return code %d',16,1);
END;
END;
COMMIT;
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0 ROLLBACK;
THROW;
END CATCH;
You can use an EXISTS checking for the tablename and schema.
IF NOT EXISTS (SELECT 'table does not exist' FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = N'2015_10_2'AND TABLE_SCHEMA = 'dbo')
BEGIN
RAISERROR('The table doesn''t exist!!!!', 16, 1)
END
sp_rename won't make you lose table contents, it will just change the table reference name and update all it's contraints and indexes references. It will also raise an error if the table to rename does not exist. Maybe what you want is to wrap your process in a transaction and rollback if something fails.
EDIT:
For basic transaction handling you can use the following. Please read the documentation for using transaction, it might take a while to know how it works correctly.
IF OBJECT_ID('tempdb..#Test') IS NOT NULL
DROP TABLE #Test
CREATE TABLE #Test (Number INT)
SELECT AmountRecords = COUNT(1) FROM #Test -- AmountRecords = 0
BEGIN TRY
BEGIN TRANSACTION
-- Do your statements here
INSERT INTO #Test (Number)
VALUES (1)
DECLARE #errorVariable INT = CONVERT(INT, 'NotAnInteger!!') -- Example of error: can't convert
COMMIT
END TRY
BEGIN CATCH -- If something goes wrong
IF ##TRANCOUNT > 0 -- ... and transaction is still open
ROLLBACK -- Revert statements from the BEGIN TRANSACTION onwards
END CATCH
SELECT AmountRecords = COUNT(1) FROM #Test -- AmountRecords = 0 (the transaction was rolled back and the INSERT reverted)
Basically you use BEGIN TRANSACTION to initiate a restore point to go back to if something fails. Then use a COMMIT once you know everything is OK (from that point onwards, other users will see the changes and modifications will be persisted). If something fails (you need TRY/CATCH block to handle errors) you can issue a ROLLBACK to revert your changes.
I have a large sql script designed so that it is 'safe' to run on different instances, or on the same instance multiple times without causing any bad data or errors
When writing such scripts I have always depended on syntax like:
if not exists (select 1 from SYS.FOREIGN_KEYS where NAME = 'FK_BAR')
begin
alter table [MyTable]
add constraint FK_BAR foreign key (some_id) references Other_Table(some_id)
end
go
This usually works pretty well. However, I recently encountered a scenario where I am unable to prevent errors from being thrown during execution. In the below code, the column "deprecated_column" has been dropped from table Foo:
if exists (select 1 from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'Foo' and COLUMN_NAME = 'deprecated_column')
and exists (select 1 from [Foo] where new_column is null)
begin
declare #updated int set #updated = 1;
while #updated > 0
begin
update top (500000)
Foo
set new_column = deprecated_column
where new_column is null
;
set #updated = ##rowcount;
end
end
go
If I run the two exist's within the if independently of this program, they return "no results" as expected, which means the inner code will never be executed. However, when I run the script, the server throws the error: Invalid column name 'deprecated_column'., and the script is marked as completing with error, which causes an alert to be raised on our system (ie, the DBA is notified and has to check), which is causing some unnecessary overhead on what should be a simple automated task.
Is there some syntax that I have overlooked that would allow this code to run without error in all cases?
As I explained in the comments, T-SQL is a compiled language and "Invalid Column" is a compiler error, not an execution error. However, since most T-SQL is only compiled right before execution, that's when you usually see it.
Since T-SQL tries to compile all of the code regardless of IF branches, the only immediate way around this is with dynamic SQL. Like so:
if exists (select 1 from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = 'Foo' and COLUMN_NAME = 'deprecated_column')
and exists (select 1 from [Foo] where new_column is null)
begin
EXEC('
declare #updated int set #updated = 1;
while #updated > 0
begin
update top (500000)
Foo
set new_column = deprecated_column
where new_column is null
;
set #updated = ##rowcount;
end
');
end
go
I have a trigger in mssql in which I want to compare each column from the inserted table with the deleted table to check if the value has changed...
If the value has changed I want to insert the column name into a temp table.
My code until now:
declare columnCursor CURSOR FOR
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'MyTable' AND TABLE_SCHEMA='dbo'
--save inserted and deleted into temp tables
select * into #row1 from Inserted
select * into #row2 from Deleted
declare #tmp table(column_name nvarchar(max))
declare #column nvarchar(50)
OPEN COlumnCUrsor
FETCH NEXT FROM ColumnCursor INTO #column
while ##FETCH_STATUS=0 begin
declare #out bit
declare #sql nvarchar(max) = N'
select #out = case when r1.'+#column+'r2.'+#column+' then 1 else 0 end
from #row1 r1
left join #row2 r2 on r1.sys_volgnr=r2.sys_volgnr'
exec sp_executesql #sql,N'#out bit OUTPUT', #out=#out OUTPUT
if( #out = 1 ) begin
insert into #tmp VALUES(#column)
end
FETCH NEXT FROM ColumnCursor INTO #column
end
CLOSE ColumnCursor;
DEALLOCATE ColumnCursor;
Is there an easier way to accomplish this?
Yes, there is.
You can use the COLUMNS_UPDATED function to determine the columns that had actually changed values, though it's not a very friendly function in terms of code readability.
Read this article from Microsoft support called Proper Use of the COLUMNS_UPDATED() Function to see what I mean.
I've came across an article called A More Performant Alternative To COLUMNS_UPDATED(), perhaps it can help you or at least inspire you.
I will note that you should resist the temptation to use the UPDATE() function, as it may return true even if no data was changed.
here is the relevant part from it's MSDN page:
UPDATE() returns TRUE regardless of whether an INSERT or UPDATE attempt is successful.
Looks like you're trying to build a dynamic solution, which might be useful if you expect to change often (=new columns to be added etc). You could do something like this (in pseudo-code)
Build a dynamic SQL based on DMVs (INFORMATION_SCHEMA.COLUMNS) for the column names:
insert into table ...
select
function_to_split_by_comma (
case when I.col1 = U.col1 then 'col1,' else '' end +
case when I.col2 = U.col2 then 'col2,' else '' end +
...
)
where
I.key_column1 = U.key_column1 ...
These names (col1, col2) should be the columns from the DMV query, + the case for each of the row, and then fixed SQL part for the beginning + you'll need to figure out how to join inserted and deleted, which requires the primary key.
For splitting the data into rows, you can use for example the delimited_split_8k by Jeff Moden (http://www.sqlservercentral.com/articles/Tally+Table/72993/).
Also as Damien pointed out, there can be more than one row in the inserted / deleted tables.
I am generating a script for automatically migrating changes from multiple development databases to staging/production. Basically, it takes a bunch of change-scripts, and merges them into a single script, wrapping each script in a IF whatever BEGIN ... END statement.
However, some of the scripts require a GO statement so that, for instance, the SQL parser knows about a new column after it's created.
ALTER TABLE dbo.EMPLOYEE
ADD COLUMN EMP_IS_ADMIN BIT NOT NULL
GO -- Necessary, or next line will generate "Unknown column: EMP_IS_ADMIN"
UPDATE dbo.EMPLOYEE SET EMP_IS_ADMIN = whatever
However, once I wrap that in an IF block:
IF whatever
BEGIN
ALTER TABLE dbo.EMPLOYEE ADD COLUMN EMP_IS_ADMIN BIT NOT NULL
GO
UPDATE dbo.EMPLOYEE SET EMP_IS_ADMIN = whatever
END
It fails because I am sending a BEGIN with no matching END. However, if I remove the GO it complains again about an unknown column.
Is there any way to create and update the same column within a single IF block?
I had the same problem and finally managed to solve it using SET NOEXEC.
IF not whatever
BEGIN
SET NOEXEC ON;
END
ALTER TABLE dbo.EMPLOYEE ADD COLUMN EMP_IS_ADMIN BIT NOT NULL
GO
UPDATE dbo.EMPLOYEE SET EMP_IS_ADMIN = whatever
SET NOEXEC OFF;
GO is not SQL - it is simply a batch separator used in some MS SQL tools.
If you don't use that, you need to ensure the statements are executed separately - either in different batches or by using dynamic SQL for the population (thanks #gbn):
IF whatever
BEGIN
ALTER TABLE dbo.EMPLOYEE ADD COLUMN EMP_IS_ADMIN BIT NOT NULL;
EXEC ('UPDATE dbo.EMPLOYEE SET EMP_IS_ADMIN = whatever')
END
You could try sp_executesql, splitting the contents between each GO statement into a separate string to be executed, as demonstrated in the example below. Also, there is a #statementNo variable to track which statement is being executed for easy debugging where an exception occurred. The line numbers will be relative to the beginning of the relevant statement number that caused the error.
BEGIN TRAN
DECLARE #statementNo INT
BEGIN TRY
IF 1=1
BEGIN
SET #statementNo = 1
EXEC sp_executesql
N' ALTER TABLE dbo.EMPLOYEE
ADD COLUMN EMP_IS_ADMIN BIT NOT NULL'
SET #statementNo = 2
EXEC sp_executesql
N' UPDATE dbo.EMPLOYEE
SET EMP_IS_ADMIN = 1'
SET #statementNo = 3
EXEC sp_executesql
N' UPDATE dbo.EMPLOYEE
SET EMP_IS_ADMIN = 1x'
END
END TRY
BEGIN CATCH
PRINT 'Error occurred on line ' + cast(ERROR_LINE() as varchar(10))
+ ' of ' + 'statement # ' + cast(#statementNo as varchar(10))
+ ': ' + ERROR_MESSAGE()
-- error occurred, so rollback the transaction
ROLLBACK
END CATCH
-- if we were successful, we should still have a transaction, so commit it
IF ##TRANCOUNT > 0
COMMIT
You can also easily execute multi-line statements, as demonstrated in the example above, by simply wrapping them in single quotes ('). Don't forget to escape any single quotes contained inside the string with a double single-quote ('') when generating the scripts.
You can enclose the statements in BEGIN and END instead of the GO inbetween
IF COL_LENGTH('Employees','EMP_IS_ADMIN') IS NULL --Column does not exist
BEGIN
BEGIN
ALTER TABLE dbo.Employees ADD EMP_IS_ADMIN BIT
END
BEGIN
UPDATE EMPLOYEES SET EMP_IS_ADMIN = 0
END
END
(Tested on Northwind database)
Edit: (Probably tested on SQL2012)
I ultimately got it to work by replacing every instance of GO on its own line with
END
GO
---Automatic replacement of GO keyword, need to recheck IF conditional:
IF whatever
BEGIN
This is greatly preferable to wrapping every group of statements in a string, but is still far from ideal. If anyone finds a better solution, post it and I'll accept it instead.
You may try this solution:
if exists(
SELECT...
)
BEGIN
PRINT 'NOT RUN'
RETURN
END
--if upper code not true
ALTER...
GO
UPDATE...
GO
I have used RAISERROR in the past for this
IF NOT whatever BEGIN
RAISERROR('YOU''RE ALL SET, and sorry for the error!', 20, -1) WITH LOG
END
ALTER TABLE dbo.EMPLOYEE ADD COLUMN EMP_IS_ADMIN BIT NOT NULL
GO
UPDATE dbo.EMPLOYEE SET EMP_IS_ADMIN = whatever
You can incorporate a GOTO and LABEL statements to skip over code, thus leaving the GO keywords intact.
I am writing a stored procedure which iterates over all of the databases on the server and populates a table variable with an aggregate of the data from some of the different databases. Some databases I'm not interested in as they are irrelevant. The problem is when my CURSOR iterates through those databases I don't care about, a SELECT statement is issued on a table that doesn't exist. How can I ignore the Invalid object name exception and continue with my processing?
Edit:
Here is how I was attempting to skip over databases that were irrelevant:
DECLARE db_cursor CURSOR FOR
SELECT name
FROM MASTER.dbo.sysdatabases
WHERE name NOT IN ('master','model','msdb','tempdb')
OPEN db_cursor
FETCH NEXT FROM db_cursor INTO #currentDatabaseName
WHILE ##FETCH_STATUS = 0
BEGIN
SET #sql = 'SELECT COUNT(Name) FROM ' + #currentDatabaseName + '.sys.Tables WHERE Name = ''SomeTableICareAbout'''
INSERT INTO #tableSearchResult
EXEC sp_executesql #sql
SET #tableCount = (SELECT COUNT(*) FROM #tableSearchResult WHERE TableCount = 1)
--If the table I care about was found, then do the good stuff
IF #tableCount > 0
...
The problem with this approach is if the executing user (in my case a service account) does not have access to SELECT on the table, then I never know about that error. If the user doesn't have SELECT access, I want that exception to be raised. But, even if the user doesn't have SELECT access, it can SELECT on the sys.Tables view.
You can't catch error 208 directly because it's a name resolution error that is raised at compilation time and before the code is actually executed. The behaviour is documented: see the section called "Errors Unaffected by a TRY…CATCH Construct" for an explanation, and the answers to this question have some interesting comments.
In addition to the 'solution' in the documentation, you can use dynamic SQL; the error will be caught in this example:
begin try
exec('select * from dbo.ThisTableDoesNotExist');
end try
begin catch
select error_number();
end catch;
If you're looping through all databases, there's a good chance you're using dynamic SQL somewhere anyway, so this might suit your case better.
You can catch the error if you are doing it inside a stored procedure (Example documented Here: http://msdn.microsoft.com/en-us/library/ms175976.aspx
Also you can change your dynamic sql to do something like this
SET #sql = '
If Exists(Select Name From ' + #currentDatabaseName + '.sys.Tables
WHERE Name = ''SomeTableICareAbout'')' --+
--Add Whatever the Good Stuff is
EXEC sp_executesql #sql
But checking if the table exists first, instead of doing the select count(1) from the table, will prevent that error from being raised.