Im working on a stored procedure, which should reward every 3rd person with a extra bonus on his current credit. Amount of bonus and (3rd person) option should be parameterized. Among is a my current code, but when I try to execute this with SQLFiddle, I get always the error Incorrect syntax near 'INTEGER'. - but I can't find out the mistake in my code. I'm using MS SQL Server 2014.
CREATE TABLE Customer (
custnr INTEGER PRIMARY KEY IDENTITY,
name VARCHAR(40) NOT NULL,
firstname VARCHAR(40) NOT NULL,
credit DECIMAL(12,2)
);
CREATE PROCEDURE awardBonus
#position INTEGER;
#bonus DECIMAL(5,2)
AS
BEGIN
DECLARE #creditCustomer DECIMAL(12,2);
DECLARE customer_cursor CURSOR FOR
SELECT custnr
FROM Customer
ORDER BY custnr ASC;
OPEN customer_cursor;
FETCH NEXT FROM customer_cursor INTO #custnr;
WHILE ##FETCH_STATUS = 0
BEGIN
IF (#custnr % #position = 0)
BEGIN
SELECT #creditCustomer = credit
FROM Customer
WHERE custnr = #custnr;
SET #creditCustomer = #creditCustomer + #bonus;
UPDATE Customer
SET credit = #creditCustomer
WHERE custnr = #custnr;
END;
FETCH NEXT FROM customer_cursor INTO #custnr;
END;
CLOSE customer_cursor;
DEALLOCATE customer_cursor;
END;
EXECUTE awardBonus 3, 100
You need to remove the ; in the parameter list:
#position INTEGER;
Also, you should declare first #custnr:
DECLARE #custnr INT;
You also have an invalid column name error in your ORDER BY clause:
ORDER BY knr ASC;
should be:
ORDER BY custnr ASC;
Not so fast!
You can rewrite this in a set-based fashion and remove the use of CURSOR
CREATE PROCEDURE awardBonus
#position INTEGER,
#bonus DECIMAL(5,2)
AS
BEGIN
WITH Cte AS(
SELECT *,
rn = ROW_NUMBER() OVER(ORDER BY custnr)
FROM Customer
)
UPDATE Cte
SET credit = credit + #bonus
WHERE
rn % #position = 0
END
CREATE PROCEDURE awardBonus
#position INTEGER;
#bonus DECIMAL(5,2)
there is a semicolon after integer should be a comma
corrected version
CREATE PROCEDURE awardBonus
#position INTEGER,
#bonus DECIMAL(5,2)
On a different note, how are you selecting the 3rd person, should this be a random selection or ordered? And why are you using the Cursor, the set based solutions seems to be a better choice. In both random or not cases you could construct the query using ROW_NUMBER() and select 3rd record for example.
You've got a ; where you need a ,:
CREATE PROCEDURE awardBonus
#position INTEGER;
#bonus DECIMAL(5,2)
Furthermore, CREATE PROCEDURE must be the only statement in a batch. So you'll have to create the table in a separate batch.
Also, you use ORDER BY knr ASC, knr does not exist.
You also use a variable #custnr which is not declared.
Related
I have a table that stores an Id, a datetime and an int crescent value. This value increases until it "breaks" and returns to a 0-near value. Ex: ...1000, 1200, 1350, 8, 10, 25...
I need to count how many times this "overflow" happens, BUT... I'm talking about a table that stores 200k rows per day!
I had already solved it! But using a procedure with a cursor that iterates over it with a while-loop. But I KNOW it isn't the faster way to do it.
Can someone help me to find some another way?
Thanks!
->
Table structure:
Id Bigint Primary Key, CreatedAt DateTime, Value Not Null Int.
Problem:
If Delta-Value between two consecutive rows is < 0, increase a counter.
Table has 200k new rows every-day.
No trigger allowed.
[FIRST EDIT]
Table has the actual structure:
CREATE TABLE ValuesLog (
Id BIGINT PRIMARY KEY,
Machine BIGINT,
CreatedAt DATETIME,
Value INT
)
I need:
To check when the [Value] of some [Machine] suddenly decreases.
Some users said to used LEAD/LAG. But it has a problem... if I chose many machines, the LEAD/LAG fuctions doesn't care about "what machine it is". So, if I find for machine-1 and machine-2, if machine-1 increase but the machine-2 descrease, LEAD/LAG will give me a false positive.
So, how my table actually looks:
Many rows of the actual table
(The image above are selecting for 3 ou 4 machines. But, IN THIS EXAMPLE, the machines are not messed up. But can occurs! And in this case, LEAD/LAG doesn't care if the line above are machine-1 or machine-2)
What I want:
In that line 85, the [value] breaks and restart. Id like to count every occorrence when it happens, the selected machines.
So:
"Machine-1 restarted 6 times... Machine-9 restarted 10 times..."
I had done something LIKE this:
CREATE PROCEDURE CountProduction #Machine INT_ARRAY READONLY, #Start DATETIME, #End DATETIME AS
SET NOCOUNT ON
-- Declare counter and insert start values
DECLARE #Counter TABLE(
machine INT PRIMARY KEY,
lastValue BIGINT DEFAULT 0,
count BIGINT DEFAULT 0
)
INSERT INTO #Counter(machine) SELECT n FROM #Machine
-- Declare cursor to iteract over results of values log
DECLARE valueCursor CURSOR LOCAL FOR
SELECT
Value,
Aux.LastValue,
Aux.count
FROM
ValueLog,
#Machine AS Machine,
#Counter AS Counter
WHERE
ValueLog.Machine = Machine.n
AND Counter.machine = ValueLog.Machine
AND ValueLog.DateCreate BETWEEN #Start AND #End;
-- Start iteration
OPEN valueCursor
DECLARE #RowMachine INT
DECLARE #RowValue BIGINT
DECLARE #RowLastValue BIGINT
DECLARE #RowCount BIGINT
FETCH NEXT FROM valueCursor INTO #RowMachine, #RowValue, #RowLastValue, #RowCount
-- Iteration
DECLARE #increment INT
WHILE ##FETCH_STATUS = 0
BEGIN
IF #RowValue < #RowLastValue
SET #increment = 1
ELSE
SET #increment = 0
-- Update counters
UPDATE
#Counter
SET
lastValue = #RowValue,
count = count + #increment
WHERE
inj = #RowMachine
-- Proceed to iteration
FETCH NEXT FROM valueCursor INTO #RowMachine, #RowValue, #RowLastValue, #RowCount
END
-- Closing iteration
CLOSE valueCursor
DEALLOCATE valueCursor
SELECT machine, count FROM #Counter
Use LEAD(). If the next row < current row, count that occurrence.
Solved using #jeroen-mostert suggested
DECLARE #Start DATETIME
DECLARE #End DATETIME
SET #Start = '2019-01-01'
SET #End = GETDATE()
SELECT
Machine,
COUNT(DeltaValue) AS Prod
FROM
(SELECT
Log.Machine,
Log.Value - LAG(Log.Value) OVER (PARTITION BY Log.Machine ORDER BY Log.Id) AS DeltaValue
FROM
ValueLog AS Log,
(SELECT
Id,
Machine,
Value
FROM
ValueLog
) AS AuxLog
WHERE
AuxLog.Id = Log.Id
AND Proto.DateCreate BETWEEN #Start AND #End
AND Proto.Machine IN (1, 9, 10)
) as TB1
WHERE
DeltaValue < 0
GROUP BY
Machine
ORDER BY
Machine
In this case, the inner LAG/LEAD function didn't mess up the content (what happened for some reason when I created a view... I'll try to understand later).
Thanks everybody! I'm new at DB, and this question make me crazy for a whole day.
I am just new in SQL language and still studying it. I'm having hard time looking for answer on how can I use the stored procedure and insert value into a table.
I have this stored procedure:
CREATE PROCEDURE TestID
AS
SET NOCOUNT ON;
BEGIN
DECLARE #NewID VARCHAR(30),
#GenID INT,
#BrgyCode VARCHAR(5) = '23548'
SET #GenID = (SELECT TOP (1) NextID
FROM dbo.RandomIDs
WHERE IsUsed = 0
ORDER BY RowNumber)
SET #NewID = #BrgyCode + '-' + CAST(#GenID AS VARCHAR (30))
UPDATE dbo.RandomIDs
SET dbo.RandomIDs.IsUsed = 1
WHERE dbo.RandomIDs.NextID = #GenID
SELECT #NewID
END;
and what I'm trying to do is this:
INSERT INTO dbo.Residents([ResidentID], NewResidentID, [ResLogdate],
...
SELECT
[ResidentID],
EXEC TestID ,
[ResLogdate],
....
FROM
source.dbo.Resident;
There is a table dbo.RandomIDs containing random 6 digit non repeating numbers where I'm pulling out the value via the stored procedure and updating the IsUsed column of the table to 1. I'm transferring data from one database to another database and doing some processing on the data while transferring. Part of the processing is generating a new ID with the required format.
But I can't get it to work Sad I've been searching the net for hours now but I'm not getting the information that I need and that the reason for my writing. I hope someone could help me with this.
Thanks,
Darren
your question is little bit confusing, because you have not explained what you want to do. As i got your question, you want to fetch random id from randomids table and after performed some processing on nextid you want to insert it into resident table [newresidentid] and end of the procedure you fetch data from resident table. if i get anything wrong feel free to ask me.
your procedure solution is following.
CREATE PROCEDURE [TestId]
AS
SET NOCOUNT ON;
BEGIN
DECLARE #NEWID NVARCHAR(30)
DECLARE #GENID BIGINT
DECLARE #BRGYCODE VARCHAR(5) = '23548'
DECLARE #COUNT INTEGER
DECLARE #ERR NVARCHAR(20) = 'NO IDS IN RANDOM ID'
SET #COUNT = (SELECT COUNT(NEXTID) FROM RandomIds WHERE [IsUsed] = 0)
SET #GENID = (SELECT TOP(1) [NEXTID] FROM RandomIds WHERE [IsUsed] = 0 ORDER BY [ID] ASC)
--SELECT #GENID AS ID
IF #COUNT = 0
BEGIN
SELECT #ERR AS ERROR
END
ELSE
BEGIN
SET #NEWID = #BRGYCODE + '-' + CAST(#GENID AS varchar(30))
UPDATE RandomIds SET [IsUsed] = 1 WHERE [NextId] = #GENID
INSERT INTO Residents ([NewResidentId] , [ResLogDate] ) VALUES (#NEWID , GETDATE())
SELECT * FROM Residents
END
END
this procedure will fetch data from your randomids table and perform some processing on nextid than after it directs insert it into resident table and if you want to insert some data through user you can use parameter after declaring procedure name
E.G
CREATE PROCEDURE [TESTID]
#PARAM1 DATATYPE,
#PARAM2 DATATYPE
AS
BEGIN
END
I'm not convinced that your requirement is a good one but here is a way to do it.
Bear in mind that concurrent sessions will not be able to read your update until it is committed so you have to kind of "lock" the update so you will get a block until you're going to commit or rollback. This is rubbish for concurrency, but that's a side effect of this requirement.
declare #cap table ( capturedValue int);
declare #GENID int;
update top (1) RandomIds set IsUsed=1
output inserted.NextID into #cap
where IsUsed=0;
set #GENID =(select max( capturedValue) from #cap )
A better way would be to use an IDENTITY or SEQUENCE to solve your problem. This would leave gaps but help concurrency.
To begin - I am new at SQL; be gentle.
I work with a school district and have recently been given "the keys" to access the database. I am interested in getting a list of students, and then generating a list of passwords for them. I have found some code which allows me to generate random passwords that I would like to incorporate into a SQL query which is gathering information from our Student database. (Thank you if this code is yours!)
My issue is that I have not been able to use the variables to create a different password for each record. I get the same randomly generated password for each student. (On a good note; at least the password changes each time I execute the query.)
I should mention that I have two accounts set up for the database access; one to simply read the information, and another with full editing rights. (I have only used this once and closed my eyes as I pushed the big red button to update some trivial information).
Results from the first run:
Name Password
JACEK mtwsz2ybu
CARL mtwsz2ybu
LARS mtwsz2ybu
Results from the second run:
Name Password
JACEK je4tm5ptw
CARL je4tm5ptw
LARS je4tm5ptw
This is the query I am running:
USE XXTableXX
DECLARE #position int, #string char(100), #length int,
#rand int, #newstring char(15), #newchar char(15);
SET #position = 1;
SET #string = 'abcdefghijkmnopqrstuvwxyz23456789';
SET #length = 9;
SET #newstring = ''
SET #newchar = ''
WHILE #position <= #length
BEGIN
SET #rand = FLOOR(RAND()*(33-1)+1);
SET #newchar = SUBSTRING(#string,#rand,1);
SET #newstring = STUFF(#newstring,len(#newstring)+1,1,#newchar)
SET #position = #position +1;
END;
SELECT DISTINCT s.firstname, #newstring AS [Password]
FROM XXStudentTableXX s
Put all the stuff above the query in a function and call the function in your query. A side note, it will execute for each row, which means a bit of a performance hit for large sets.
Here is a way to do this.
First, you will need to make the RAND() into it's own view since you can't call it from a function
CREATE VIEW [dbo].[NewRandom]
AS
SELECT RAND() AS [RandSeed]
GO
Now you must create your function that uses the view. This function accepts an integer so you can do variable password lengths. You can hardcode it in your query or take out the parameter and hard code it in the function.
CREATE FUNCTION [dbo].[ufn_GeneratePassword] ( #PasswordLength INT )
RETURNS VARCHAR(20)
AS
BEGIN
DECLARE #position int, #string char(100), #length int,
#rand int, #newstring char(15), #newchar char(15);
SET #position = 1;
SET #string = 'abcdefghijkmnopqrstuvwxyz23456789';
SET #length = #PasswordLength;
SET #newstring = ''
SET #newchar = ''
WHILE #position <= #length
BEGIN
SET #rand = FLOOR((SELECT RandSeed FROM dbo.[NewRandom])*(33-1)+1);
SET #newchar = SUBSTRING(#string,#rand,1);
SET #newstring = STUFF(#newstring,len(#newstring)+1,1,#newchar)
SET #position = #position +1;
END
RETURN #newstring
END
Now you can call the function on every row of your table
SELECT DISTINCT s.firstname, [dbo].[ufn_GeneratePassword](9) AS [Password]
FROM XXStudentTableXX s
I think what you will need to do for this is create a table, or table variable, then instead of selecting make it insert into the table. Also Add a loop that loops 1x for each student ID. This will then insert 1 row for each student and run the randomizer 1 time.
First covert your procedure into a scalar SQL function.
CREATE VIEW dbo.RandomNumberView
AS
SELECT RandomNumber = RAND();
GO
CREATE FUNCTION dbo.GeneratePassword()
RETURNS char(15)
AS
-- Generates and Returns a random password
BEGIN
DECLARE #position int, #string char(100), #length int,
#rand int, #newstring char(15), #newchar char(15);
SET #position = 1;
SET #string = 'abcdefghijkmnopqrstuvwxyz23456789';
SET #length = 9;
SET #newstring = ''
SET #newchar = ''
WHILE #position <= #length
BEGIN
SELECT #rand = FLOOR(RandomNumber *(33-1)+1) FROM RandomNumberView;
SET #newchar = SUBSTRING(#string,#rand,1);
SET #newstring = STUFF(#newstring,len(#newstring)+1,1,#newchar)
SET #position = #position +1;
END;
RETURN #newstring;
END;
GO
And then you can easily use it whatever way you want.
SELECT DISTINCT s.firstname, dbo.GeneratePassword() AS [Password]
FROM XXStudentTableXX s
Note that each time you run this query you would get different password against the same record. I would prefer to use this function to only generate and insert password in the table and not as a direct select statement.
To get the data from a random table, SQL Server provides the NEWID () function. As its name says every execution is generated a new GUID (Global Unique Identifier), these GUIDs are unique, so the value of the order will never be the same.
Therefore you do not need to create a random function that does it for you. So you may have your answer using a simple SQL.
CREATE TABLE STUDENT (
[ID] INT IDENTITY (1, 1) NOT NULL,
[NAME] NVARCHAR (100) NULL
);
INSERT INTO STUDENT (NAME) VALUES ('John');
INSERT INTO STUDENT (NAME) VALUES ('Carl');
INSERT INTO STUDENT (NAME) VALUES ('Mary');
INSERT INTO STUDENT (NAME) VALUES ('Joan');
select
ID
,NAME
,CONCAT(
CAST((ABS(CHECKSUM(NEWID()))%10) as varchar(1))
, CHAR(ASCII('a') + (ABS(CHECKSUM(NEWID())) % 25))
, CHAR(ASCII('A') + (ABS(CHECKSUM(NEWID())) % 25))
, LEFT(LOWER(NEWID()),2)
, LEFT(NEWID(),2)
, LEFT(LOWER(NEWID()),2)
) AS PASSWORD
from STUDENT
SQL Fiddle
However, you may wish to Make your own generator taking into account a high level of complexity generated password.
https://www.simple-talk.com/blogs/2009/09/30/strong-password-generator/
It inserted a first row successfully but it's not inserting any other row, though second row has no conflict of primary key
Code in my aspx.cs file:
outputParVal = sqlCmd.Parameters[outputParName].Value;
outparameter in stored procedure is--- "Result"
CREATE PROCEDURE [dbo].[RecruiterProfileInsert]
#CompanyId int,
#CompanyName varchar(200),
#EmailId varchar(50) ,
#Password varchar(20) ,
#ContactNumber varchar(15),
#Website varchar(50),
#CompanyProfile varchar(2000),
#IsVerified bit,
#Result Tinyint OutPut
--#CreatedDate datetime ,
--UpdatedDate datetime
AS
BEGIN
-- Insert statements for procedure here
--check whether #CompanyName already exist or not if exist then return
IF EXISTS(SELECT Top 1 * FROM RecruiterProfile WHERE #CompanyId = LTRIM(RTRIM(#CompanyId)))
BEGIN
SET #Result = 0-- Already Exists
END
ELSE
BEGIN
INSERT INTO RecruiterProfile
(
CompanyId,
CompanyName,
EmailId ,
Password ,
ContactNumber,
Website ,
CompanyProfile ,
IsVerified,
CreatedDate
)
VALUES
(
#CompanyId,
#CompanyName,
#EmailId ,
#Password,
#ContactNumber,
#Website,
#CompanyProfile,
#IsVerified,
GetDate()
)
set #Result =1
return
END
END
This is the problem:
SELECT Top 1 * FROM RecruiterProfile WHERE #CompanyId = LTRIM(RTRIM(#CompanyId))
This inherently makes no sense. You're comparing the variable to itself. Take the # sign out of one of the CompanyId references. The RTrim is unnecessary in SQL Server, and the LTrim doesn't make sense either because the later insert doesn't also LTrim so something is going to go wrong eventually.
Furthermore, inside of an EXISTS clause, TOP makes no sense unless you are using ORDER BY and doing something with the final result. Just do SELECT * inside of EXISTS clauses.
One more thing: if there is high concurrency and users could possibly try to insert the same thing at the same time, your query could still fail on a duplicate key violation.
Is there a way to make a TSQL variable constant?
No, but you can create a function and hardcode it in there and use that.
Here is an example:
CREATE FUNCTION fnConstant()
RETURNS INT
AS
BEGIN
RETURN 2
END
GO
SELECT dbo.fnConstant()
One solution, offered by Jared Ko is to use pseudo-constants.
As explained in SQL Server: Variables, Parameters or Literals? Or… Constants?:
Pseudo-Constants are not variables or parameters. Instead, they're simply views with one row, and enough columns to support your constants. With these simple rules, the SQL Engine completely ignores the value of the view but still builds an execution plan based on its value. The execution plan doesn't even show a join to the view!
Create like this:
CREATE SCHEMA ShipMethod
GO
-- Each view can only have one row.
-- Create one column for each desired constant.
-- Each column is restricted to a single value.
CREATE VIEW ShipMethod.ShipMethodID AS
SELECT CAST(1 AS INT) AS [XRQ - TRUCK GROUND]
,CAST(2 AS INT) AS [ZY - EXPRESS]
,CAST(3 AS INT) AS [OVERSEAS - DELUXE]
,CAST(4 AS INT) AS [OVERNIGHT J-FAST]
,CAST(5 AS INT) AS [CARGO TRANSPORT 5]
Then use like this:
SELECT h.*
FROM Sales.SalesOrderHeader h
JOIN ShipMethod.ShipMethodID const
ON h.ShipMethodID = const.[OVERNIGHT J-FAST]
Or like this:
SELECT h.*
FROM Sales.SalesOrderHeader h
WHERE h.ShipMethodID = (SELECT TOP 1 [OVERNIGHT J-FAST] FROM ShipMethod.ShipMethodID)
My workaround to missing constans is to give hints about the value to the optimizer.
DECLARE #Constant INT = 123;
SELECT *
FROM [some_relation]
WHERE [some_attribute] = #Constant
OPTION( OPTIMIZE FOR (#Constant = 123))
This tells the query compiler to treat the variable as if it was a constant when creating the execution plan. The down side is that you have to define the value twice.
No, but good old naming conventions should be used.
declare #MY_VALUE as int
There is no built-in support for constants in T-SQL. You could use SQLMenace's approach to simulate it (though you can never be sure whether someone else has overwritten the function to return something else…), or possibly write a table containing constants, as suggested over here. Perhaps write a trigger that rolls back any changes to the ConstantValue column?
Prior to using a SQL function run the following script to see the differences in performance:
IF OBJECT_ID('fnFalse') IS NOT NULL
DROP FUNCTION fnFalse
GO
IF OBJECT_ID('fnTrue') IS NOT NULL
DROP FUNCTION fnTrue
GO
CREATE FUNCTION fnTrue() RETURNS INT WITH SCHEMABINDING
AS
BEGIN
RETURN 1
END
GO
CREATE FUNCTION fnFalse() RETURNS INT WITH SCHEMABINDING
AS
BEGIN
RETURN ~ dbo.fnTrue()
END
GO
DECLARE #TimeStart DATETIME = GETDATE()
DECLARE #Count INT = 100000
WHILE #Count > 0 BEGIN
SET #Count -= 1
DECLARE #Value BIT
SELECT #Value = dbo.fnTrue()
IF #Value = 1
SELECT #Value = dbo.fnFalse()
END
DECLARE #TimeEnd DATETIME = GETDATE()
PRINT CAST(DATEDIFF(ms, #TimeStart, #TimeEnd) AS VARCHAR) + ' elapsed, using function'
GO
DECLARE #TimeStart DATETIME = GETDATE()
DECLARE #Count INT = 100000
DECLARE #FALSE AS BIT = 0
DECLARE #TRUE AS BIT = ~ #FALSE
WHILE #Count > 0 BEGIN
SET #Count -= 1
DECLARE #Value BIT
SELECT #Value = #TRUE
IF #Value = 1
SELECT #Value = #FALSE
END
DECLARE #TimeEnd DATETIME = GETDATE()
PRINT CAST(DATEDIFF(ms, #TimeStart, #TimeEnd) AS VARCHAR) + ' elapsed, using local variable'
GO
DECLARE #TimeStart DATETIME = GETDATE()
DECLARE #Count INT = 100000
WHILE #Count > 0 BEGIN
SET #Count -= 1
DECLARE #Value BIT
SELECT #Value = 1
IF #Value = 1
SELECT #Value = 0
END
DECLARE #TimeEnd DATETIME = GETDATE()
PRINT CAST(DATEDIFF(ms, #TimeStart, #TimeEnd) AS VARCHAR) + ' elapsed, using hard coded values'
GO
If you are interested in getting optimal execution plan for a value in the variable you can use a dynamic sql code. It makes the variable constant.
DECLARE #var varchar(100) = 'some text'
DECLARE #sql varchar(MAX)
SET #sql = 'SELECT * FROM table WHERE col = '''+#var+''''
EXEC (#sql)
For enums or simple constants, a view with a single row has great performance and compile time checking / dependency tracking ( cause its a column name )
See Jared Ko's blog post https://blogs.msdn.microsoft.com/sql_server_appendix_z/2013/09/16/sql-server-variables-parameters-or-literals-or-constants/
create the view
CREATE VIEW ShipMethods AS
SELECT CAST(1 AS INT) AS [XRQ - TRUCK GROUND]
,CAST(2 AS INT) AS [ZY - EXPRESS]
,CAST(3 AS INT) AS [OVERSEAS - DELUXE]
, CAST(4 AS INT) AS [OVERNIGHT J-FAST]
,CAST(5 AS INT) AS [CARGO TRANSPORT 5]
use the view
SELECT h.*
FROM Sales.SalesOrderHeader
WHERE ShipMethodID = ( select [OVERNIGHT J-FAST] from ShipMethods )
Okay, lets see
Constants are immutable values which are known at compile time and do not change for the life of the program
that means you can never have a constant in SQL Server
declare #myvalue as int
set #myvalue = 5
set #myvalue = 10--oops we just changed it
the value just changed
Since there is no build in support for constants, my solution is very simple.
Since this is not supported:
Declare Constant #supplement int = 240
SELECT price + #supplement
FROM what_does_it_cost
I would simply convert it to
SELECT price + 240/*CONSTANT:supplement*/
FROM what_does_it_cost
Obviously, this relies on the whole thing (the value without trailing space and the comment) to be unique. Changing it is possible with a global search and replace.
There are no such thing as "creating a constant" in database literature. Constants exist as they are and often called values. One can declare a variable and assign a value (constant) to it. From a scholastic view:
DECLARE #two INT
SET #two = 2
Here #two is a variable and 2 is a value/constant.
SQLServer 2022 (currently only as Preview available) is now able to Inline the function proposed by SQLMenace, this should prevent the performance hit described by some comments.
CREATE FUNCTION fnConstant() RETURNS INT AS BEGIN RETURN 2 END GO
SELECT is_inlineable FROM sys.sql_modules WHERE [object_id]=OBJECT_ID('dbo.fnConstant');
is_inlineable
1
SELECT dbo.fnConstant()
ExecutionPlan
To test if it also uses the value coming from the Function, I added a second function returning value "1"
CREATE FUNCTION fnConstant1()
RETURNS INT
AS
BEGIN
RETURN 1
END
GO
Create Temp Table with about 500k rows with Value 1 and 4 rows with Value 2:
DROP TABLE IF EXISTS #temp ;
create table #temp (value_int INT)
DECLARE #counter INT;
SET #counter = 0
WHILE #counter <= 500000
BEGIN
INSERT INTO #temp VALUES (1);
SET #counter = #counter +1
END
SET #counter = 0
WHILE #counter <= 3
BEGIN
INSERT INTO #temp VALUES (2);
SET #counter = #counter +1
END
create index i_temp on #temp (value_int);
Using the describe plan we can see that the Optimizer expects 500k values for
select * from #temp where value_int = dbo.fnConstant1(); --Returns 500001 rows
Constant 1
and 4 rows for
select * from #temp where value_int = dbo.fnConstant(); --Returns 4rows
Constant 2
Robert's performance test is interesting. And even in late 2022, the scalar functions are much slower (by an order of magnitude) than variables or literals. A view (as suggested mbobka) is somewhere in-between when used for this same test.
That said, using a loop like that in SQL Server is not something I'd ever do, because I'd normally be operating on a whole set.
In SQL 2019, if you use schema-bound functions in a set operation, the difference is much less noticeable.
I created and populated a test table:
create table #testTable (id int identity(1, 1) primary key, value tinyint);
And changed the test so that instead of looping and changing a variable, it queries the test table and returns true or false depending on the value in the test table, e.g.:
insert #testTable(value)
select case when value > 127
then #FALSE
else #TRUE
end
from #testTable with(nolock)
I tested 5 scenarios:
hard-coded values
local variables
scalar functions
a view
a table-valued function
running the test 10 times, yielded the following results:
scenario
min
max
avg
scalar functions
233
259
240
hard-coded values
236
265
243
local variables
235
278
245
table-valued function
243
272
253
view
244
267
254
Suggesting to me, that for set-based work in (at least) 2019 and better, there's not much in it.
set nocount on;
go
-- create test data table
drop table if exists #testTable;
create table #testTable (id int identity(1, 1) primary key, value tinyint);
-- populate test data
insert #testTable (value)
select top (1000000) convert(binary (1), newid())
from sys.all_objects a
, sys.all_objects b
go
-- scalar function for True
drop function if exists fnTrue;
go
create function dbo.fnTrue() returns bit with schemabinding as
begin
return 1
end
go
-- scalar function for False
drop function if exists fnFalse;
go
create function dbo.fnFalse () returns bit with schemabinding as
begin
return 0
end
go
-- table-valued function for booleans
drop function if exists dbo.tvfBoolean;
go
create function tvfBoolean() returns table with schemabinding as
return
select convert(bit, 1) as true, convert(bit, 0) as false
go
-- view for booleans
drop view if exists dbo.viewBoolean;
go
create view dbo.viewBoolean with schemabinding as
select convert(bit, 1) as true, convert(bit, 0) as false
go
-- create table for results
drop table if exists #testResults
create table #testResults (id int identity(1,1), test int, elapsed bigint, message varchar(1000));
-- define tests
declare #tests table(testNumber int, description nvarchar(100), sql nvarchar(max))
insert #tests values
(1, N'hard-coded values', N'
declare #testTable table (id int, value bit);
insert #testTable(id, value)
select id, case when t.value > 127
then 0
else 1
end
from #testTable t')
, (2, N'local variables', N'
declare #FALSE as bit = 0
declare #TRUE as bit = 1
declare #testTable table (id int, value bit);
insert #testTable(id, value)
select id, case when t.value > 127
then #FALSE
else #TRUE
end
from #testTable t'),
(3, N'scalar functions', N'
declare #testTable table (id int, value bit);
insert #testTable(id, value)
select id, case when t.value > 127
then dbo.fnFalse()
else dbo.fnTrue()
end
from #testTable t'),
(4, N'view', N'
declare #testTable table (id int, value bit);
insert #testTable(id, value)
select id, case when value > 127
then b.false
else b.true
end
from #testTable t with(nolock), viewBoolean b'),
(5, N'table-valued function', N'
declare #testTable table (id int, value bit);
insert #testTable(id, value)
select id, case when value > 127
then b.false
else b.true
end
from #testTable with(nolock), dbo.tvfBoolean() b')
;
declare #testNumber int, #description varchar(100), #sql nvarchar(max)
declare #testRuns int = 10;
-- execute tests
while #testRuns > 0 begin
set #testRuns -= 1
declare testCursor cursor for select testNumber, description, sql from #tests;
open testCursor
fetch next from testCursor into #testNumber, #description, #sql
while ##FETCH_STATUS = 0 begin
declare #TimeStart datetime2(7) = sysdatetime();
execute sp_executesql #sql;
declare #TimeEnd datetime2(7) = sysdatetime()
insert #testResults(test, elapsed, message)
select #testNumber, datediff_big(ms, #TimeStart, #TimeEnd), #description
fetch next from testCursor into #testNumber, #description, #sql
end
close testCursor
deallocate testCursor
end
-- display results
select test, message, count(*) runs, min(elapsed) as min, max(elapsed) as max, avg(elapsed) as avg
from #testResults
group by test, message
order by avg(elapsed);
The best answer is from SQLMenace according to the requirement if that is to create a temporary constant for use within scripts, i.e. across multiple GO statements/batches.
Just create the procedure in the tempdb then you have no impact on the target database.
One practical example of this is a database create script which writes a control value at the end of the script containing the logical schema version. At the top of the file are some comments with change history etc... But in practice most developers will forget to scroll down and update the schema version at the bottom of the file.
Using the above code allows a visible schema version constant to be defined at the top before the database script (copied from the generate scripts feature of SSMS) creates the database but used at the end. This is right in the face of the developer next to the change history and other comments, so they are very likely to update it.
For example:
use tempdb
go
create function dbo.MySchemaVersion()
returns int
as
begin
return 123
end
go
use master
go
-- Big long database create script with multiple batches...
print 'Creating database schema version ' + CAST(tempdb.dbo.MySchemaVersion() as NVARCHAR) + '...'
go
-- ...
go
-- ...
go
use MyDatabase
go
-- Update schema version with constant at end (not normally possible as GO puts
-- local #variables out of scope)
insert MyConfigTable values ('SchemaVersion', tempdb.dbo.MySchemaVersion())
go
-- Clean-up
use tempdb
drop function MySchemaVersion
go