Reading inserted column names and values in a TSQL trigger - tsql

I've been asked to create history tables for every table in a database. Then create a trigger that will write to the history table whenever the primary table is updated.
The history tables have the same structure as the primary table, but with a couple of extra rows ('id' and 'update type')
I've never done anything with triggers before, but I would like to do is dynamically go through the columns in 'Inserted' and construct an insert statement to populate the history table.
However I cannot work out how to read the names of the columns and their individual values.
My half finished trigger currently looks like...
CREATE TRIGGER tr_address_history
ON address
FOR UPDATE
AS
DECLARE #colCount int
DECLARE #maxCols int
SET #colCount = 0
SET #maxCols = (SELECT COUNT(column_name) FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME = 'Inserted')
PRINT 'Number of columns = ' + CONVERT(varChar(10),#maxCols)
WHILE (#colCount <= #maxCols)
BEGIN
DECLARE #name varchar(255)
SELECT #name = column_name FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME = 'Inserted'
DECLARE #value varchar(255)
SELECT #value = #name FROM Inserted
PRINT 'name = ' + #name + ' and value = ' + #value
SET #colCount = #colCount + 1
END
PRINT 'Done';
When the trigger runs it just says "Number of columns = 0"
Can anyone tell me what's wrong with :
SELECT COUNT(column_name) FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME = 'Inserted'
Thanks...

First solution proposed by Beenay25 is good, but you should use affected table instead of 'inserted' pseudotable.
This is:
SELECT #name = column_name FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME = 'AFFECTED_TABLE'
Instead of 'INSERTED'
Also, you should use dynamic SQL.
This will be a complete working solution:
ALTER TRIGGER [dbo].[tr_address_history]
ON [dbo].[address]
AFTER Insert
AS
DECLARE #ColumnName nvarchar(500)
DECLARE #TableName nvarchar(500)
DECLARE #value nvarchar(500)
DECLARE #Sql nvarchar(500)
Set #TableName='address'
DECLARE ColumnsCursor CURSOR FOR
select column_name FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME = 'address'
OPEN ColumnsCursor
FETCH NEXT FROM ColumnsCursor into #ColumnName
WHILE ##FETCH_STATUS=0
BEGIN
select * into #tmp from inserted
Set #Sql= 'SELECT #value =' + #ColumnName + ' FROM #tmp'
EXEC sp_executesql #Sql, N'#Value nvarchar(500) OUTPUT', #Value OUTPUT
DROP TABLE #TMP
print '[' + #ColumnName +'='+ ltrim(rtrim(#Value))+']'
FETCH NEXT FROM ColumnsCursor into #ColumnName
END
CLOSE ColumnsCursor
DEALLOCATE ColumnsCursor

The 'inserted' table is a pseudo-table; it doesn't appear in INFORMATION_SCHEMA.
There is the UPDATE() operator for use in triggers:
CREATE TRIGGER trigger_name ON tablename
FOR UPDATE
AS
SET NOCOUNT ON
IF (UPDATE(Column1) OR UPDATE(Column2))
BEGIN
your sql here
END
COLUMNS_UPDATED
UPDATE()

There is a way to do what the questioner requires:
I have made something inside a trigger that tests whether all the columns of a particular table actually participated in an insert to that table. If they did, I later copied them to a history table. If they did not, then rollback and print only complete rows may be inserted into the report table. Perhaps they could adapt this to their needs:
here it is:
[
if exists (select 1 from inserted) and not exists (select 1 from deleted) -- if an insert has been performed
begin -- and we want to test whether all the columns in the report table were included in the insert
declare #inserted_columncount int, #actual_num_of_columns int, #loop_columns int, #current_columnname nvarchar(300),
#sql_test nvarchar(max), #params nvarchar(max), #is_there bit
set #actual_num_of_columns = (
select count(*) from (
select COLUMN_NAME
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'renameFilesFromTable_report') as z)
set #inserted_columncount = 0
set #loop_columns = 1
declare inserted_columnnames cursor scroll for -- these are not really the inserted ones, but we are going to test them 1 by 1
select COLUMN_NAME
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'renameFilesFromTable_report'
set #params = '#is_there_in bit output'
open inserted_columnnames
fetch next from inserted_columnnames into #current_columnname
select * into #temp_for_dynamic_sql from inserted -- this is necessary because the scope of sp_executesql does not include inserted pseudo table
while (#loop_columns <= #actual_num_of_columns) -- looping with independent integer arithmetic
begin
set #sql_test = '
set #is_there_in = 0
if exists (select ['+#current_columnname+'] from #temp_for_dynamic_sql where ['+#current_columnname+'] is not null)
set #is_there_in = 1'
exec sp_executesql #sql_test, #params, #is_there output
if #is_there = 1
begin
fetch next from inserted_columnnames into #current_columnname
set #inserted_columncount = #inserted_columncount + 1
set #loop_columns = #loop_columns + 1
end
else if #is_there <> 1
begin
fetch next from inserted_columnnames into #current_columnname
set #loop_columns = #loop_columns + 1
end
end
close inserted_columnnames
deallocate inserted_columnnames
-- at this point we hold in two int variables the number of columns participating in the insert and the total number of columns
]
Then you can simply do if #inserted_columncount < #actual_num_of_columns ..........
I did this because i have a sp that inserts 1 complete line to the report table every time it runs. That's fine, but i don't want anyone else touching that table by mistake. not even myself. I also want to keep history. So i made this trigger to keep the history but also to check if an insert was attempted without values for all the columns in the report table, and further down the code it checks if an update or delete was attempted and it rollbacks.
i was thinking of expanding this to allow an update but in which all the columns are set.
this could possibly be done as follows:
if update was attempted,
and exists (
select possibly_excluded.COLUMN_NAME from (
select COLUMN_NAME
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'renameFilesFromTable_report') as possibly_excluded
group by possibly_excluded.COLUMN_NAME
having COLUMN_NAME not in (
select COLUMN_NAME
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'renameFilesFromTable_report' and
sys.fn_IsBitSetInBitmask(#ColumnsUpdated, COLUMNPROPERTY(OBJECT_ID(TABLE_SCHEMA + '.' + TABLE_NAME), COLUMN_NAME, 'ColumnID')) <> 0)
)
begin
rollback transaction
print 'Only updates that set the values for a complete row are allowed on the report table..'
end

Related

Dynamic SQL with nvarchar(max) variable (again)

I have read about a dozen articles here and I am still stumped with this issue.
I am building a dynamic select statement that will update a view on a monthly schedule.
set ansi_nulls on
go
set quoted_identifier on
go
alter procedure [dbo].[Proc_Name_SP]
as
begin
set nocount on
set quoted_identifier off
declare #dbname varchar(10), #schema_id int, #schema_name varchar(10),
#jacro varchar(10), #rec_cnt int, #tot_rec int
declare #SQL_Main nvarchar(max), #SQL_Final nvarchar(max),
#SQL_schema nvarchar(2000), #SQL_Union nvarchar(max)
declare iteration cursor global static for
-- Begin statement for cursor array
select distinct db, code
from linkedserver.db.schema.Directory
where current_stage = 'live'
order by db
-- End statement for cursor array
-- get total number of cursor iterations to know when to stop
-- "union" statements
select #tot_rec = count(*) from (select distinct db, code
from [linkedserver].db.schema.Directory
where current_stage = 'live') as cur
-- begin loop
open iteration
fetch first from iteration into #dbname, #jacro
while ##fetch_status=0
begin
-- the schema used is not consistent. Because of the linked server it was
-- necessary to get the Schema_ID from the sys.tables and then pull the
-- schema name from sys.schema
set #SQL_schema = 'select #sch_id = schema_id from [linkedserver].'+#dbname+'.sys.tables where name = ''Manuscript'''
execute sp_executesql #SQL_schema, N'#sch_id int OUTPUT', #sch_id = #schema_id output
--print #schema_id
set #SQL_schema ='select #sch_name = name from [linkedserver].'+#dbname+'.sys.schemas where schema_id = '+cast(#schema_id as varchar)+''
execute sp_executesql #SQL_schema, N'#sch_name nvarchar(10) OUTPUT', #sch_name = #schema_name output
--print #schema_name
--building Select statement
set #SQL_Main ='
select jcode.Code as BILLING_ACRO
,s.start_dt as BILLING_DATE
,cmpt_ms_nm as MANUSCRIPT
,isnull(jcode.billing_type, ''reviewed'') as Billing_type
from [linkedserver].'+#dbname+'.'+#schema_name+'.Manuscript as m
join [linkedserver].'+#dbname+'.'+#schema_name+'.Step as s on m.ms_id = s.ms_id and m.ms_rev_no = s.ms_rev_no
join (select j_id, Code, billing_type from [linkedserver].db.schema.Directory where db = '''+#dbname+''') as jcode on jcode.j_id = m.j_id
where jcode.Code = '''+#jacro+'''
and m.ms_rev_no = 0
and s.stage_id = 190
and isnull(cmpt_ms_nm, '''') <> ''''
and s.step_id = (select min(s2.step_id)
from [linkedserver].'+#dbname+'.'+#schema_name+'.Step as s2
where s2.stage_id = 190
and s2.ms_id = m.ms_id
and s2.ms_rev_no = m.ms_rev_no)
'
set #rec_cnt = isnull(#rec_cnt, 0) + 1
if #SQL_Union is null
begin
set #SQL_Union = #SQL_Main
end
else if #tot_rec <> #rec_cnt
begin
set #SQL_Union = #SQL_Union + ' union ' + #SQL_Main
end
else
begin
set #SQL_Union = #SQL_Union + #SQL_Main
end
--print #rec_cnt
fetch next from iteration into #dbname, #jacro --next database
end -- while ##FETCH_STATUS=0
close iteration
deallocate iteration
-- build new view
print len(#SQL_Union)
set #SQL_Final = '
ALTER VIEW [dbo].[View_Name_VW]
AS
'+#SQL_Union+'
'
execute sp_executesql #SQL_Final
--grab string variables to table for troubleshooting
insert into Output_SQL(SQL_Final, SQL_Final_Len, SQL_Union, SQL_Union_Len)
select #SQL_Final, LEN(#SQL_Final), #SQL_Union, LEN(#SQL_Union)
set nocount off
end
go
I have read that others have had problems with this type of truncation and I have tried multiple suggestions but in the end the I am getting capped at 68274 in this code with nvarchar(max). For troubleshooting, I am saving the results of the variables and the len of these variables to a table to eliminate the SSMS cap on the display of strings.
I have tried cast(#varible as nvarchar(max)) on the right side of the = sign. I have changed the data type lengths (as the select that is being built is not that large, it is just large after it has been union for each unique customer)
I am open to any suggestions as I have tried many variations of datatype declarations for these variables.

two table input parameters in stored procedure

I am working on C# project which needs a stored procedure which will take two table names as inputs.
First table will copy data to a temp table which has two columns URL & channelID. This URL column is then matched with other input table's URL column & if match is found then it will update channel id from temp table to other tables channel ID.
I have written stored procedure as
CREATE PROCEDURE [dbo].[UpdateTables]
#excelTable NVARCHAR(128) ,
#TableName NVARCHAR(128)
AS
Declare #channel_Id nvarchar(50)
Declare #url varchar(400)
BEGIN
Select *
Into #Temp
From QUOTENAME(#excelTable)
END
While EXISTS(SELECT * From #Temp ) > 0
Begin
Select Top 1
#channel_Id = channel_Id, #url = url
From #Temp
update QUOTENAME(#TableName)
set channelid = #channelid
where pagefullurl like '%'+ #url + '%'
Delete #Temp
Where channelid = #channelid
End
I don't have much knowledge in TSQL and my above code has errors.
Incorrect syntax near '>'.
Msg 137, Level 15, State 2, Procedure UpdateTables, Line 20
Must declare the scalar variable "#channelid".
Msg 137, Level 15, State 2, Procedure UpdateTables, Line 22
Must declare the scalar variable "#channelid".
Please suggest what changes needs to done
I don't have MS SQL server handy to test it, but you declare your variable as #channel_Id, and later try to use it as #channelid (without the underscore) so you get errors about the undeclared variable.
I've corrected your SP and this is how it should look
CREATE PROCEDURE [dbo].[UpdateTables]
#excelTable NVARCHAR(128) ,
#TableName NVARCHAR(128)
AS
Declare #channel_Id nvarchar(50)
Declare #url varchar(400)
BEGIN
Select *
Into #Temp
From QUOTENAME(#excelTable)
While EXISTS(SELECT * From #Temp )
Begin
Select Top 1
#channel_Id = channel_Id, #url = url
From #Temp
update QUOTENAME(#TableName)
set channelid = #channel_Id
where pagefullurl like '%'+ #url + '%'
Delete #Temp
Where channelid = #channel_Id
End
END

Need help in creating a stored procedure to iterate tables in a database, then run a SQL statement on each table

Our application does not delete data as we retain it for a period of time, instead we have a column "deleted" (bit) in most tables of the database that store data which we mark 1 when deleted, otherwise the default is 0.
I'd like to create a stored procedure that iterates all tables in the database, checks for the existence of a column named "deleted" and if it exists, I run a check against the LastUpdatedUtc column (datetime2) and if the date is over 6 months old and deleted = 1 then we delete the row.
This application is under continuous development so tables could be added which is why I want to create a script that iterates tables instead of having to add a line for each table and remember to add them as new tables are added.
Any help in a SQL Server 2008 R2 stored procedure to this would be a great help.
Thank you.
EDIT (thank you Omaer) here is what I've come up with so far. Anyone that knows a better way let me know.
IF OBJECT_ID('tempdb..#tmpTables') IS NOT NULL DROP TABLE #tmpTables
GO
CREATE TABLE #tmpTables
(
ID INT,
TableName NVARCHAR(100) NOT NULL
)
GO
SET NOCOUNT ON
GO
INSERT #tmpTables
SELECT [object_id], [name] FROM sys.all_objects WHERE type_desc = 'USER_TABLE' ORDER BY [name]
DECLARE #TN NVARCHAR(100)
DECLARE #SQL NVARCHAR(max)
DECLARE #PurgeDate VARCHAR(50)
SET #PurgeDate = DATEADD(MONTH, -6, GETUTCDATE())
WHILE (SELECT COUNT(*) FROM #tmpTables) > 0
BEGIN
SELECT TOP 1 #TN = TableName FROM #tmpTables
IF EXISTS(SELECT * FROM sys.columns WHERE name = 'deleted' AND OBJECT_ID = OBJECT_ID(#TN))
BEGIN
IF EXISTS(SELECT * FROM sys.columns WHERE name = 'LastUpdatedUtc' AND OBJECT_ID = OBJECT_ID(#TN))
BEGIN
SET #SQL = 'SELECT Count(*) As Counter FROM ' + #TN + ' WHERE [deleted] = 1 AND [LastUpdatedUtc] < ''' + #PurgeDate + '''' -- this will be the delete line when the code is final, just outputting results for now
EXEC(#SQL)
END
END
DELETE #tmpTables WHERE TableName=#TN
END
DROP TABLE #tmpTables
This is my first attempt, not tested it so there might be some typos/syntax errors but this should get you started:
declare #date6MonthsBack varchar(50)
select #date6MonthsBack = dateadd(month, -6, getdate());
declare c cursor for
select 'delete from ' + quotename(name) + ' where [deleted] = 1 and [LastUpdatedUtc] <= ''' + #date6MonthsBack + '''' from sys.tables
where object_id in (select object_id from sys.columns where name = 'deleted')
and object_id in (select object_id from sys.columns where name = 'LastUpdatedUtc')
declare #sql varchar(max)
open c; fetch next from c into #sql
while (##fetch_status = 0) begin
print(#sql)
--exec(#sql) --uncomment this line to do the actual deleting once you have verified the commands.
fetch next from c into #sql; end
close c; deallocate c
You could use undocummented sp_MSforeactable procedure instead of loop or cursor. Something like code below. I created procedure that runs your code and is executed with sp_MSforeachtable. The disadvantage is - the procedure is undocumented and may not be supported in next SQL Server releases
IF OBJECT_ID('dbo.usp_cleanup') IS NULL
EXEC ('CREATE PROCEDURE dbo.usp_cleanup AS SELECT 1')
GO
ALTER PROCEDURE dbo.usp_cleanup
#sTblName VARCHAR(200)
AS
BEGIN
-- your variables
DECLARE #PurgeDate VARCHAR(50)
DECLARE #SQL VARCHAR(MAX)
SET #PurgeDate = DATEADD(MONTH, -6, GETUTCDATE())
-- we can check columns existence in one condition
IF
EXISTS(SELECT * FROM sys.columns WHERE name = 'deleted' AND OBJECT_ID = OBJECT_ID(#sTblName))
AND EXISTS(SELECT * FROM sys.columns WHERE name = 'LastUpdatedUtc' AND OBJECT_ID = OBJECT_ID(#sTblName))
BEGIN
SET #SQL = 'SQL CODE GOES HERE' -- this will be the delete line when the code is final, just outputting results for now
PRINT #SQL
--EXEC(#SQL) -- uncomment for execution
END
ELSE
-- for debugging
BEGIN
PRINT #sTblName + ' has no [delete] and [LastUpdatedUtc] columns'
END
END
EXEC sp_MSforeachtable 'exec usp_cleanup ''?'''
GO

T-SQL passing a table name dynamically inside WITH statement

I have the following code in T-SQL that reads table names from a cursor.
But I have problem with the scoping table name variable inside the WITH statement.
I can run this code when I explicitly set dbo.#sys_name to a synonym name like dbo.mysysnonym but when I put it as variable name like dbo.#syn_name it does not work.
-- drop duplicates records from synonyms
DECLARE #syn_name varchar(50)
DECLARE s_cursor CURSOR FOR
SELECT name
FROM sys.synonyms
WHERE base_object_name LIKE 'xyz%'
OPEN s_cursor;
FETCH NEXT FROM s_cursor INTO #syn_name;
WHILE ##FETCH_STATUS = 0
BEGIN
FETCH NEXT FROM s_cursor INTO #syn_name;
WITH dedupTable AS
(
SELECT
sys_id,
row_number() OVER (PARTITION BY sys_id ORDER BY sys_id) AS nr
FROM
dbo.#syn_name
)
DELETE FROM dedupTable
WHERE nr > 1
END;
CLOSE s_cursor
DEALLOCATE s_cursor
As far as I know, you cannot use variables as table names, so dbo.#syn_name will not work in a FROM clause. Instead, you will have to use Dynamic SQL.
Something like:
...
FETCH NEXT FROM s_cursor INTO #syn_name;
DECLARE #sql nvarchar(4000)
SET #sql = N'
WITH dedupTable
AS (
SELECT sys_id, row_number()
OVER ( PARTITION BY sys_id ORDER BY sys_id ) AS nr
FROM dbo.' + #syn_name + '
)
DELETE FROM dedupTable
WHERE nr > 1'
EXEC sp_executesql #sql

How to get row count from EXEC() in a TSQL SPROC?

I have a TSQL sproc that builds a query as and executes it as follows:
EXEC (#sqlTop + #sqlBody + #sqlBottom)
#sqlTop contains something like SELECT TOP(x) col1, col2, col3...
TOP(x) will limit the rows returned, so later I want to know what the actual number of rows in the table is that match the query.
I then replace #sqlTop with something like:
EXEC ('SELECT #ActualNumberOfResults = COUNT(*) ' + #sqlBody)
I can see why this is not working, and why a value not declared error occurs, but I think it adequately describes what I'm trying to accomplish.
Any ideas?
use sp_executesql and an output parameter
example
DECLARE #sqlBody VARCHAR(500),#TableCount INT, #SQL NVARCHAR(1000)
SELECT #sqlBody = 'from sysobjects'
SELECT #SQL = N'SELECT #TableCount = COUNT(*) ' + #sqlBody
EXEC sp_executesql #SQL, N'#TableCount INT OUTPUT', #TableCount OUTPUT
SELECT #TableCount
GO
You could instead have the dynamic query return the result as a row set, which you would then insert into a table variable (could be a temporary or ordinary table as well) using the INSERT ... EXEC syntax. Afterwards you can just read the saved value into a variable using SELECT #var = ...:
DECLARE #rowcount TABLE (Value int);
INSERT INTO #rowcount
EXEC('SELECT COUNT(*) ' + #sqlBody);
SELECT #ActualNumberOfResults = Value FROM #rowcount;
Late in the day, but I found this method much simpler:
-- test setup
DECLARE #sqlBody nvarchar(max) = N'SELECT MyField FROM dbo.MyTable WHERE MyOtherField = ''x''';
DECLARE #ActualNumberOfResults int;
-- the goods
EXEC sp_executesql #sqlBody;
SET #ActualNumberOfResults = ##ROWCOUNT;
SELECT #ActualNumberOfResults;
After executing your actual query store the result of ##ROWCOUNT in any variable which you can use later.
EXEC sp_executesql 'SELECT TOP 10 FROM ABX'
SET #TotRecord = ##ROWCOUNT into your variable for later use.
Keep in mind that dynamic SQL has its own scope. Any variable declared/modified there will go out of scope after your EXEC or your sp_executesql.
Suggest writing to a temp table, which will be in scope to your dynamic SQL statement, and outside.
Perhaps put it in your sqlBottom:
CREATE TABLE ##tempCounter(MyNum int);
EXEC('SELECT #ActualNumberOfResults = COUNT(*) ' + #sqlBody +
'; INSERT INTO ##tempCounter(MyNum) VALUES(#ActualNumberOfResults);');
SELECT MyNum FROM ##tempCounter;
You can use output variable in SP_EXECUTESQL
DECLARE #SQL NVARCHAR(MAX);
DECLARE #ParamDefinition NVARCHAR(100) = '#ROW_SQL INT OUTPUT'
DECLARE #AFFECTED_ROWS INT;
SELECT
#SQL = N'SELECT 1 UNION ALL SELECT 2'
SELECT #SQL += 'SELECT #ROW_SQL = ##ROWCOUNT;';
EXEC SP_EXECUTESQL #SQL, #ParamDefinition, #ROW_SQL=#AFFECTED_ROWS OUTPUT;
PRINT 'Number of affected rows: ' + CAST(#AFFECTED_ROWS AS VARCHAR(20));
Ouput:
SQL2.sql: Number of affected rows: 2
Thanks Jesus Fernandez!
The only problem with the answers that create temporary tables (either using "DECLARE #rowcount TABLE" or "CREATE TABLE ##tempCounter(MyNum int)") is that you're having to read all the affected records off disk into memory. If you're expecting a large number of records this may take some time.
So if the answer is likely to be large the "use sp_executesql and an output parameter" solution is a more efficient answer. And it does appear to work.