I want to run the following SELECT query:
DECLARE #ColumnName nvarchar(50)
SET #ColumnName = 'AlarmID' -- actually these are calculated
-- by another SELECT but this isn't relevant
SELECT MIN(#ColumnName) FROM INSERTED
This doesn't work, it returns the value of #ColumnName instead of the actual data. How can I make this work?
I cannot put the SELECT into a string and run it with sp_executesql because I will lose access to the INSERTED table (this is running in a trigger).
EXEC('SELECT MIN(' + #ColumnName + ') FROM INSERTED')
Derived from the link smoore provided.
Use this if you want the minimum as a variable:
SELECT #columnName = MIN(#ColumnName) FROM YourTable
You can't really do that. Your best bet, depending on number of possible values of #ColumnName, is to dynamically set the field value with a case statement, or selectively run the right query using an IF statement:
SELECT CASE #ColumnName WHEN 'AlarmID' THEN MIN(AlarmID) WHEN 'AnotherField' THEN
MIN(AnotherField) END AS MinimumValue FROM INSERTED
OR
IF #ColumnName = 'AlarmID'
SELECT MIN(AlarmID) FROM INSERTED
ELSE
....
Related
I'm using a search object query (found on the internet, wish I could give credit to the developer) to search database for the columns needed when I write queries. The output search object query allows me to enter the type of table to look in (partial name) as well as the column name (partial name) I'm trying to find. I've been attempting to modify the search object query so it returns the 1st value (Top 1) it finds. This would help me to easily see at a glance if the column has the particular type of data I'm looking for.
I've attempted to write it both as a stored procedure that I could pass two parameters (partial table and partial column name) and I've also tried using dynamic SQL (my first attempt at using it, so I'm a novice when it comes to use it). I had moderate success with the use of dynamic SQL, but can only get it to produce one result rather than be called multiple times for all the results in my search object output. The code I used is shown here:
-- This is the search object query found on internet
Use masterdb
Select a.name, b.name
From sysobjects a
Inner Join syscolumns b On a.id = b.id
Where b.name like '%Result%'
And a.name like '%Lab%'
Order By a.name, b.name
-- This is a separate query I used to test calling the data with dynamic SQL
DECLARE #value VARCHAR(100), #tablename VARCHAR(100)
SET #value = 'Result'
SET #tablename = 'LabSpecimen'
DECLARE #sqlText NVARCHAR(1000);
SET #sqlText = N'SELECT Top 1 ' + #value + ' FROM testndb.dbo.' + #tablename
EXEC (#sqlText)
If I use the search object query and search for tables that have lab and column names that have result, I might get output like this:
LabMain,ResultID
LabSpecimen,ResultCategory
LabSpecimen,ResultDate
LabSpecimen,Results
I would like to have the search object query pull data from the table in the first column and the column name in the 2nd column and return the first value it finds to give me a sample output for the given column name/table. Output would look like this:
LabMain,ResultID,E201812310001
LabSpecimen,ResultCategory,ExampleCategory
LabSpecimen,ResultDate,20181231
LabSpecimen,Results,34.20
Okay, I really didn't want to have to post an answer to this, but here goes.
So, the first, really-really-huge thing is: SQL Injection. SQL Injection is the #1 security vulnerability for something like a dozen years running, per OWASP. Basically, SQL Injection is where you use dynamic SQL that has any fragment of the sql command being populated by a user. So in the OP's case, this section here:
SET #value = 'Result'
SET #tablename = 'LabSpecimen'
DECLARE #sqlText NVARCHAR(1000);
SET #sqlText = N'SELECT Top 1 ' + #value + ' FROM testndb.dbo.' + #tablename
EXEC (#sqlText)
... if the end incarnation would be that #tableName and #value are populated by the user as part of their search? Then the user can do a 'search' that ends up injecting sql statements that the server runs directly; for a cheap example, imagine this for #value:
3' ; drop table #tableName --
... which would go ahead and drop every table that matches the #tablename you passed in.
Anyway, so, as we go through this problem, we're going to keep SQL Injection in mind at every step.
Problem #1: How to get the tables/columns that match.
You pretty much already nailed this. The only thing missing is to put it into a temp table so that you can loop through it (and limit it down to U-types, since otherwise you'll get stored procs and system tables.) I went ahead and had it also hit the Schema information - that way, if you have tables in different schemas, it'll still be able to get the results.
declare #tableNameFragment varchar(100) -- note: these top 4 lines will eventually
declare #columnNameFragment varchar(100) -- be changed to stored proc args
set #tableNameFragment = 'Performance' -- and populated by the user calling
set #columnNameFragment = 'status' -- the proc (instead of hard-coded.)
declare #entityMatches TABLE (TableName varchar(200), ColName varchar(128))
insert into #entityMatches
Select sch.TABLE_SCHEMA + '.' + sysobj.name as TableName, syscol.name as ColName
From sysobjects sysobj
Join syscolumns syscol On sysobj.id = syscol.id
Join INFORMATION_SCHEMA.TABLES sch on sch.TABLE_NAME = sysobj.name
where sysobj.xtype = 'U'
and (sysobj.name like '%' + isnull(#tableNameFragment,'') + '%')
and (syscol.name like '%' + isnull(#columnNameFragment,'') + '%')
Now, notice that while #tableNameFragment and #columnNameFragment are used, they're not used in a dynamic query. It doesn't matter if the user puts in something malicious into those values
Problem #2 - How to loop through your table
Basically, you're going to need a cursor. I hate cursors, but sometimes (like this one), they're necessary.
Problem #3 - How to actually do a dynamic query and get a result back
This is actually trickier than it looks. You can't do a raw EXEC() for a return value, nor can you simply have the cmd you're executing populating a variable - because EXEC (and SP_ExecuteSql operate in a different context, so they can't populate variables outside in your script.)
You need to use SP_ExecuteSQL, but specify a return variable getting populated by the interior sql command. For example:
declare #sqlCmd nvarchar(max)
declare #dynamicReturn varchar(max)
set #sqlCmd = 'select #retVal=1'
EXEC Sp_executesql #sqlCmd,
N'#retVal varchar(max) output',
#dynamicReturn output
select #dynamicReturn
Problem #4 - How to write your Dynamic command
Here's where things get dicey, since it's where we're using a dynamic SQL command. The important thing here is: you cannot use anything the user provided as an input. Which means, you can't use the variables #tableNameFragment or #columnNameFragment. You can use the values in the #entityMatches table, though. Why? Because the user didn't populate them. They got populated by the data in the sys tables - it doesn't matter if the user puts something nefarious in the input variables, that #entityMatches data simply holds the existing table/column names that match.
Also important: When you're working on code that could be a problem if a future dev down the line tweaks or copies/pastes - you should put comment warnings to illuminate the issue.
So, putting it all together? You'll have something that looks like this:
declare #tableNameFragment varchar(100) -- note: these top 4 lines will eventually
declare #columnNameFragment varchar(100) -- be changed to stored proc args
set #tableNameFragment = 'Performance' -- and populated by the user calling
set #columnNameFragment = 'status' -- the proc (instead of hard-coded.)
declare #entityMatches TABLE (TableName varchar(200), ColName varchar(128))
insert into #entityMatches
Select sch.TABLE_SCHEMA + '.' + sysobj.name as TableName, syscol.name as ColName
From sysobjects sysobj
Join syscolumns syscol On sysobj.id = syscol.id
Join INFORMATION_SCHEMA.TABLES sch on sch.TABLE_NAME = sysobj.name
where sysobj.xtype = 'U'
and (sysobj.name like '%' + isnull(#tableNameFragment,'') + '%')
and (syscol.name like '%' + isnull(#columnNameFragment,'') + '%')
declare #returnResults TABLE (TableName varchar(200), ColName varchar(128), FirstValue varchar(max))
declare Cur Cursor For select TableName,ColName from #entityMatches
declare #cursorTable varchar(200), #cursorColumn varchar(128)
open Cur
fetch Next from cur into #cursorTable,#cursorColumn
while ##FETCH_STATUS = 0
begin
-- Note: the variables #cursorTable, #cursorColumn are NOT user populated
-- but instead are populated from the Sys tables. Because of this,
-- this dynamic sql below is not SQL-Injection vulnerable (the entries
-- are not populated from user entry of any sort.)
-- Be very careful modifying the lines below to make sure you don't
-- introduce a vulnerability.
declare #sqlCmd nvarchar(max)
declare #dynamicReturn varchar(max)
set #sqlCmd = 'select top 1 #retVal=[' + #cursorColumn + '] from ' + #cursorTable
EXEC Sp_executesql #sqlCmd,
N'#retVal varchar(max) output',
#dynamicReturn output
insert into #returnResults values (#cursorTable, #cursorColumn, #dynamicReturn)
fetch Next from cur into #cursorTable,#cursorColumn
End
close cur
deallocate cur
select * from #returnResults
Create a stored procedure like below mention stored procedure.
Get the table and column name from sysobject & syscolumn and add it in hash table on the base of parameter of stored procedure. After that declare a cursor and in loop of cursor create a dynamic query of column and table name and get first row of current column from table of cursor loop. After that execute the query and update the result in the hash table. At the end of lookup select the Record from hash table. Check the below stored procedure. I hope that its helpful for you.
Create procedure Sp_GetSampleData
#TName varchar(200) = ''
as
Select
a.name TableName, b.name ColumnName,
CAST('' as varchar(max)) as SampleValue
into
#Tbl
from
sysobjects a
inner join
syscolumns b on a.id = b.id
where
(#TName='' or a.name = #TName)
order ny
a.name, b.name
declare #TableName varchar(200), #ColumnName varchar(200),
#sqlText nvarchar(max), #Val varchar(max)
declare Cur Cursor For
select TableName, ColumnName
from #Tbl
open Cur
fetch Next from cur into #TableName,#ColumnName
while ##FETCH_STATUS =0
begin
set #sqlText=''
set #Val=''
SET #sqlText = N'SELECT Top 1 #Val=[' + #ColumnName + '] FROM testndb.dbo.' + #TableName
EXEC Sp_executesql
#sqlText,
N'#Val varchar(max) output',
#Val output
print #sqlText
update #Tbl set SampleValue=#Val where TableName=#TableName and ColumnName =#ColumnName
fetch Next from cur into #TableName,#ColumnName
End
close cur
deallocate cur
select * from #Tbl
I ask for your help because I can not determine a solution to this problem. I am using SQL Server 2014.
I have a query like this:
SELECT
event_id,
CONCAT ('week', CHARINDEX('Y', weeks), '_date') AS num
FROM
CT_EVENT
which returns a week number of the form: week1_date
This value is the name of a column in another table. What I would like to do is a subrequest to get the value that is in it.
SELECT week1_date
FROM CT_CONFIG
I looked for a way to 'caster' a string in column name without actually finding.
Thank you in advance, and remain available for any supplement.
Jérémy
You cannot use Sub-query here, you will need to use Dynamic sql, something like this...
Declare #ColumnName SYSNAME
, #Sql NVARCHAR(MAX);
SELECT #ColumnName = CONCAT ('week', CHARINDEX ('Y', weeks), '_date')
FROM CT_EVENT
SET #Sql = N' SELECT ' + QUOTENAME(#ColumnName) + N' FROM CT_CONFIG;'
Exec sp_executesql #Sql;
i need to concatenate all rows to display in a single string
i wrote the same query for other table it works
both queries gives me a last row value only
declare #varaibelName nvarchar(max)
set #cpx=''
Select #varaibelName=COALESCE(#varaibelName,'')+ FeildName From TableName
select #varaibelName
or
declare #varaibelName nvarchar(max)
set #varaibelName=''
Select #varaibelName=#varaibelName+ FeildName From TableName
select #varaibelName
That would be because your second to last value is NULL, so it'll effectively set the parameter to NULL, and then fetch the last remaining row.
See fiddle here for example.
To fix that, you can prepare for the null with for example ISNULL, like so (replace the SQL in the fiddle with this, and see what happens):
declare #variableName nvarchar(max)
Select #variableName=COALESCE(#variableName,'')+ ISNULL(FieldName,'') From TableName
select #variableName
Better yet, you probably want to separate the columns from each other, so you can do this to add a comma inbetween them, then parse the extra comma off from the end of the string:
declare #variableName nvarchar(max)
Select #variableName=COALESCE(#variableName,'')+ ISNULL(FieldName+', ','') From TableName
select #variableName = SUBSTRING(#variableName, 1, LEN(#variableName)-1)
select #variableName
EDIT:
HoneyBadger is absolutely right, in his comment below. Since I'm having a brainfart day regarding COALESCE, might as well go with this to avoid pointlessly using both:
declare #variableName nvarchar(max) set #variableName = ''
Select #variableName= #variableName + ISNULL(FieldName+', ','') From TableName
select #variableName = SUBSTRING(#variableName, 1, LEN(#variableName)-1)
select #variableName
I need to write a query engine on a web app, what needs to be accomplish is that a user can enter any SELECT statement into a textbox and then the results should be created into a new table.
This is my function I have created but it only support SQL Server 2012 and I want similar to this function but only it should support SQL Server 2005 and above:
CREATE FUNCTION [dbo].[CustomQueryTableCreation]
(
#TableName varchar(max),
#sql NVARCHAR(MAX)
)
RETURNS
#TableBuilder TABLE
(
DS varchar(max)
)
BEGIN
INSERT INTO #TableBuilder
SELECT 'CREATE TABLE dbo.' + #TableName+'(';
INSERT INTO #TableBuilder
SELECT
CASE column_ordinal
WHEN 1 THEN '' ELSE ',' END
+ name + ' ' + system_type_name + CASE is_nullable
WHEN 0 THEN ' not null' ELSE '' END
FROM
sys.dm_exec_describe_first_result_set
(
#sql, NULL, 0
) AS f
ORDER BY
column_ordinal;
INSERT INTO #TableBuilder
SELECT ');';
RETURN
END
What I want to do now is that I want to search through my query and replace the FIRST FROM with INTO NewTable FROM.
The query can contain multiple joins.
Should I control this with SQL or C#?
I had a similar problem with the 2005 Environment. If you save the Select query to a table, and use the following built in procedure to execute the query:
EXECUTE sp_executesql #Query
Here is the MS docs:
http://msdn.microsoft.com/en-us/library/ms188001%28v=sql.90%29.aspx
Edit
Keeping this in mind, can take the SQL dumps and Create OpenRowset Queries to take the SQL and dump them into a TempTable, and from the Temp Table to a permanent table if required.
I created the following SP's to assist with getting the info to a permanent table.
First the procedure to execute the specific SQL Statement
CREATE PROCEDURE [dbo].[spExecuteRowset]
(
#Query NVARCHAR(MAX)
)
AS
BEGIN
--Execute SQL Statement
EXECUTE sp_executesql #Query
END
Then the OpenRowset SP:
CREATE PROCEDURE [dbo].[spCustomquery]
(
#ProQuery NVARCHAR(MAX),
#Tablename NVARCHAR(MAX)
)
AS
BEGIN
--Insert the info into a Specidied Table
DECLARE #Query NVARCHAR(max)
SET #Query = 'SELECT * INTO #MyTempTable FROM OPENROWSET(''SQLNCLI'', ''Server=localhost;Trusted_Connection=yes;'','' EXEC [YOUR DATABASE].dbo.spExecuteRowset' +''''+#ProQuery+''''') SELECT * INTO '+ #Tablename +' FROM #MyTempTable'
--FOR DEBUG ONLY!!!!
PRINT #Query
EXEC [YourDatabase].dbo.spExecuteRowset #Query
END
This takes it from the #tempTable to A Physical Table.
Here are some docs on OpenRowset.
You have no guarantee that the first from in a query will accept an into, because you can have a subselect in the select statement. In addition, you could have a field name like datefrom that throws things off too.
But, assuming you have "simple" SQL statements, you can do it as:
select stuff(#query, charindex('from ', #query), 0, 'into '+#Table+' ')
from t;
EDIT:
The following is what you really want to do:
select *
into #Table
from (#query) q;
Using the subquery solves the problem.
This is a well-known problem. String concatenation is usually a bad/limited solution.
The more recommended solution is to let some other mechanism to return you the result set (openquery etc.), and then insert it to a table.
For example:
SELECT *
INTO YourTable
FROM OPENQUERY([LinkedServer],your query...)
In a table there are like 113 columns. and there are two default records in the table, one is for unknown and another is for inapplicable. So, each column has its own default value to represent unknown and inapplicable.
I dont wanna write regular insert statement to get those two records.
so, I tried to insert each column using a cursor.
Got the names of columns for that table from information_schema.columns and tried to insert values from exact table in another location using "insert into select" statement, but the name of the columns that we get from information_schema
Declare #col_name varchar(50)
declare my_cur CURSOR for
select column_name from information_schema.columns
where table_name = 'tabl' and table_catalog = 'db'
and table_schema = 'dbo'
Fetch next from my_cur
into #col_name
while ##FETCH_STATUS = 0
BEGIN
Insert into db.dbo.tabl (***#col_name***)
select ***#col_name*** from openrowset('sqlncli', 'server=my_server; trusted_connection=yes;', db.dbo.tabl)
fetch next from my_cur into #col_name
end
close my_cur
deallocate my_cur
go
But, I did not realize that #col_name would be treated as string, rather than object (column)
Is there any work around for this case or any alternative solution.
I think that getting these defaults populated is the least of your problems.
I'd suggest taking a look at this: Fundamentals of Relational Database Design
And if you still want to do this, it might be better to retrieve all the defaults from the linked server, place them in a temp table, and then join to information_schema.columns to populate your table. You'll probably need to transpose the data to make it work.
You will have to generate the INSERT statement as dynamic SQL and then execute it
Declare #InsertStatement VarChar (Max)
SET #InsertStatement = ''
SET #InsertStatement = #InsertStatement + ' Insert into db.dbo.tabl (' + #col_name + ') '
SET #InsertStatement = #InsertStatement + ' select ' + #col_name + ' from openrowset(''sqlncli'', ''server=my_server''; '
Exec Sp_SQLExec #InsertStatement