sql scalar functions - sql-server

I have a scalar function in my code that calls another scalar function that calls 2 other tables as detailed below. I know this must be performing like a pig. It is used throughout the database... My problem is its a little outside developing skills to rewrite this as an table valued function.
I'm attempting to win some of the developers over to rewriting the function, but we only have JAVA guys and no dedicated SQL developer, so they dont see any problems. can anyone suggest how this should be rewritten? many thanks...
CREATE FUNCTION [dbo].[getInvertCurrencyExchangeRateByDate](#casino_id char(16),#currency_code char(3), #end_date datetime)
RETURNS float AS
BEGIN
declare #retval float;
set #retval =
dbo.getCurrencyExchangeRateByDate(#casino_id,#currency_code,#end_date);
if (#retval != 0) return 1/#retval;
return 0;
END
CREATE FUNCTION [dbo].[getCurrencyExchangeRateByDate](#casino_id char(16),#currency_code char(3), #end_date datetime)
RETURNS float AS
BEGIN
declare #retval float;
declare #casino_curr_code char(3);
set #casino_curr_code =
(SELECT TOP 1 currency_code
FROM Casino
WHERE
casino_id=#casino_id
);
if (#currency_code = #casino_curr_code) return 1;
set #retval =
COALESCE(
(
SELECT TOP 1 exchange_rate
FROM CurrencyExchangeRateHistory
WHERE
casino_id=#casino_id and
currency_code=#currency_code AND
transact_time <= #end_date
ORDER BY
transact_time DESC
),0.0);
return #retval
END

I'm sorry, but thats a heck lot of code for something rather simple
I think this satisfies the query needs.
CREATE FUNCTION dbo.TVF(#casino_id char(16),#currency_code char(3), #end_date datetime)
RETURNS TABLE
AS
RETURN --IF THE JOIN FAILS OR RETURNS 0, DIVISION WILL NEVER HAPPEN AND FALL IN THE ISNULL
SELECT TOP 1 CASE WHEN A.currency_code = #currency_code THEN 1 ELSE ISNULL(1/NULLIF(B.exchange_rate,0), 0) END AS RETVAL
FROM Casino A
LEFT JOIN CurrencyExchangeRateHistory B ON A.casino_id = B.casino_id AND B.transact_time <= #end_date AND B.currency_code = A.currency_code
WHERE A.casino_id = #casino_id
ORDER BY B.transact_time DESC

Related

T-SQL : CREATE FUNCTION must be the only statement in batch [duplicate]

I'm getting this error from the function:
CREATE FUNCTION getLavel(#id int ,#lavel char)
RETURNS date
BEGIN
DECLARE #date date
select #date = (select authorization_date from Authorized WHERE diver_number = #id and #lavel =level_name)
return #date
END
GO
What can be the reason?
Ty very much.
The function needs to be either the only function in the query window OR the only statement in the batch. If there are more statements in the query window, you can make it the only one "in the batch" by surrounding it with GO's.
e.g.
GO
CREATE FUNCTION getLavel(#id int ,#lavel char)
RETURNS date
BEGIN
DECLARE #date date
select #date = (select authorization_date from Authorized WHERE diver_number = #id and #lavel =level_name)
return #date
END
GO
Turn this into an inline table valued function. This will perform better than the scalar function. Also, you should NOT use the default sizes for character datatypes. Do you know what the default length for a char is? Did you know that it can vary based on usage?
CREATE FUNCTION getLavel
(
#id int
, #lavel char --You need to define the length instead of the default length
)
RETURNS table
return
select authorization_date
from Authorized
WHERE diver_number = #id
and #lavel = level_name
GO
You need to add RETURN before the END statement
That should fix your issue, that's what fixed mine. :D
Make sure that this statement is the only the only sql in your query window before you execute it.
Or you can highlight the function declaration and execute
What solved it for me, was that I was trying to create the function inside of a transaction context - that doesn't make sense from a SQL Server point of view. Transactions are for data, not functions.
Take the CREATE FUNCTION statement out of the transaction, then wrap it in GO's
CREATE FUNCTION CalculateAge(#DOB DATE)
RETURNS INT
AS
BEGIN
DECLARE #Age INT
SET #DOB='08/12/1990'
SET #Age =DATEDIFF(YEAR,#DOB,GETDATE()) -
CASE
WHEN (MONTH (#DOB)> MONTH (GETDATE ())) OR
(MONTH (#DOB)= MONTH (GETDATE ()) AND DAY (#DOB) >DAY (GETDATE ()))
THEN 1
ELSE 0
END
SELECT #Age
END
The Error is given to you in only query Page But if you execute the query then it will successfully execute.
CREATE FUNCTION getLavel(#id int ,#lavel char)
RETURNS date
BEGIN
DECLARE #date date
select #date = (select authorization_date from Authorized WHERE diver_number = #id and #lavel = level_name)
return #date
END
GO

SQL server Function - Take column name as input parameter

I need to write a SQL function to return column specific values, so I am passing the column name as a parameter to SQL-function to return its corresponding value. Here is the sample function
CREATE FUNCTION GETDATETIME(#columnName VARCHAR(100))
RETURNS DATETIME
AS
BEGIN
RETURN (SELECT TOP 1.#columnName FROM TEST_TABLE )
END
GO
The above function seems to be straight forward, but it not working as expected.
And when I execute the function
SELECT dbo.GETDATETIME('DATETIMECOLUMNNAME')
I am getting this error:
Conversion failed when converting date and/or time from character string.
Can someone help me to identify the issue?
For that you need to write dynamic sql. But Functions won't support execute statement.
So you need to write multiple If conditions for each column.
CREATE FUNCTION GETDATETIME(#columnName VARCHAR(100))
RETURNS DATETIME
AS
BEGIN
DECLARE #RESULT DATETIME;
IF (#columnName = 'ABC')
Begin
SELECT TOP 1 #RESULT = [ABC] FROM TEST_TABLE
END
ELSE IF (#columnName = 'DEF')
Begin
SELECT TOP 1 #RESULT = [DEF] FROM TEST_TABLE
END
ELSE IF (#columnName = 'GHI')
Begin
SELECT TOP 1 #RESULT = [GHI] FROM TEST_TABLE
END
RETURN #RESULT
END
GO
Edit 2:
If your column always return Datetime, then you can do like below.
CREATE TABLE A_DUM (ID INT, STARTDATE DATETIME, ENDDATE DATETIME, MIDDLEDATE DATETIME)
INSERT INTO A_DUM
SELECT 1, '2019-07-24 11:35:58.910', '2019-07-28 11:35:58.910', '2019-07-26 11:35:58.910'
UNION ALL
SELECT 2, '2019-07-29 11:35:58.910', '2019-08-01 11:35:58.910', '2019-07-24 11:35:58.910'
And your function like below
CREATE FUNCTION GETDATETIME(#columnName VARCHAR(100))
RETURNS DATETIME
AS
BEGIN
DECLARE #RESULT DATETIME;
SELECT TOP 1 #RESULT = CAST(PROP AS DATETIME)
FROM A_DUM
UNPIVOT
(
PROP FOR VAL IN (STARTDATE, ENDDATE,MIDDLEDATE)
)UP
WHERE VAL = #columnName
RETURN #RESULT
END
GO
There's a workaround to this, similar to #Shakeer's answer - if you are attempting to GROUP BY or perform a WHERE on a column name, then you can just use a CASE statement to create a clause to match on specific column names (if you know them).
Obviously this doesn't work very well if you have many columns to hard-code, but at least it's a way to achieve the general idea.
E.g. with WHERE clause:
WHERE
(CASE
WHEN #columnname = 'FirstColumn' THEN FirstColumnCondition
WHEN #columnname = 'SecondColumn' THEN SecondColumnCondition
ELSE SomeOtherColumnCondition
END)
Or with GROUP BY:
GROUP BY
(CASE
WHEN #columnname = 'FirstColumn' THEN FirstColumnGroup
WHEN #columnname = 'SecondColumn' THEN SecondColumnGroup
ELSE SomeOtherColumnGroup
END)
No you cannot use dynamic sql in functions in SQL. Please check this link for more info link.
So it is not possible to achieve this by any function, yes you may use stored procedures with output parameter for same.
You may find this link for reference link.

SQL IF ELSE performance issue

I have a stored procedure that can get data from 2 different sources depending on if the user requests data from a single closed period (archived into a data warehouse table) or from an open period (data from transaction tables).
If I pass parameters that limit the select to the data warehouse table (providing a year and period for a closed period) the procedure takes a very long time to return results unless I comment out the ELSE BEGIN… code. No data is coming from the ELSE portion of code but it is still slowing down the procedure. If I comment out the ELSE portion of code, it is very fast.
I have tried OPTION (RECOMPILE) and I’m using local variables to avoid parameter sniffing but it’s not helping. Is there any way to get around this?
The following is an example of what I’m doing that runs slow:
IF #Year <> 0 AND #Period <> 0 AND (SELECT PerClosedTimestamp
FROM Period
WHERE
PerCompanyID = #CompanyID AND
PerYear = #Year AND
PerPeriod = #Period) IS NOT NULL
BEGIN
SELECT
datawhse.column1, datawhse.column2, etc …
FROM
datawhse
END
ELSE
BEGIN
SELECT
trantable.column1, trantable.column2, etc…
FROM
trantable
END
If I exclude the ELSE statement it runs very fast:
IF #Year <> 0
AND #Period <> 0
AND (SELECT PerClosedTimestamp
FROM Period
WHERE PerCompanyID = #CompanyID
AND PerYear = #Year
AND PerPeriod = #Period) IS NOT NULL
BEGIN
SELECT datawhse.column1
,datawhse.column2, etc …
FROM datawhse
END
Are #Year and #Period directly from the input of the stored procedure? like in your sproc definition, did you write in this following way?
create proc USP_name #Year int, #Period int as
begin
...
end
You can try using local variable, according to my experience in many cases like this, local variables help a lot.
create proc USP_name #Year int, #Period int as
begin
declare #Year_local int, #Period_local int
set #Year_local = #Year, #Period_local = #period
if #Year_local <> 0 AND #Period_local <> 0 AND ...
....
end
As mentioned in the comments, the definitive answer to why is it slow is always to be found in the query plan.
At a guess, the appearance of trantable in the procedure is biasing the query optimizer in a way that disfavors datawhse. I'd be tempted to at least try UNION ALL instead of IF/THEN, something along the lines of
SELECT
datawhse.column1, datawhse.column2, etc …
FROM
datawhse
WHERE #Year <> 0 AND #Period <> 0 AND (SELECT PerClosedTimestamp
FROM Period
WHERE
PerCompanyID = #CompanyID AND
PerYear = #Year AND
PerPeriod = #Period) IS NOT NULL
UNION ALL
SELECT
trantable.column1, trantable.column2, etc…
FROM
trantable
WHERE #Year = 0 OR #Period = 0 OR (SELECT PerClosedTimestamp
FROM Period
WHERE
PerCompanyID = #CompanyID AND
PerYear = #Year AND
PerPeriod = #Period) IS NULL
It would be interesting to see how the query plans compare.
Thanks everyone for your suggestions. I ended up creating 2 separate functions to return data from either the data warehouse table or the transaction tables. I select from the functions within the IF THEN ELSE statement and that seems to have solved my problem.

Looking for a General "Minimum" User Defined Function

I created the following function to simplify a piece of particularly complex code.
CREATE FUNCTION [dbo].[DSGetMinimumInt] (#First INT, #Second INT)
RETURNS INT
AS
BEGIN
IF #First < #Second
RETURN #First
RETURN #Second
END
However, it only works for the INT datatype. I know I could create one for numeric and possibly for Varchar and Datetime.
Is it possible to create one master "Minimum" function to deal with them all? Has anyone done this?
I've Googled it, but come up empty.
here is a basic one you can work with, I'd be careful using this in queries, as it will slow them down in proportion to the number of rows it is used on:
CREATE FUNCTION [dbo].[DSGetMinimum] (#First sql_variant, #Second sql_variant)
RETURNS varchar(8000)
AS
BEGIN
DECLARE #Value varchar(8000)
IF SQL_VARIANT_PROPERTY(#First,'BaseType')=SQL_VARIANT_PROPERTY(#Second,'BaseType')
OR #First IS NULL OR #Second IS NULL
BEGIN
IF SQL_VARIANT_PROPERTY(#First,'BaseType')='datetime'
BEGIN
IF CONVERT(datetime,#First)<CONVERT(datetime,#Second)
BEGIN
SET #Value=CONVERT(char(23),#First,121)
END
ELSE
BEGIN
SET #Value=CONVERT(char(23),#Second,121)
END
END --IF datetime
ELSE
BEGIN
IF #First < #Second
SET #Value=CONVERT(varchar(8000),#First)
ELSE
SET #Value=CONVERT(varchar(8000),#Second)
END
END --IF types the same
RETURN #Value
END
GO
EDIT
Test Code:
DECLARE #D1 datetime , #D2 datetime
DECLARE #I1 int , #I2 int
DECLARE #V1 varchar(5) , #V2 varchar(5)
SELECT #D1='1/1/2010', #D2='1/2/2010'
,#I1=5 , #I2=999
,#V1='abc' , #V2='xyz'
PRINT dbo.DSGetMinimumInt(#D1,#D2)
PRINT dbo.DSGetMinimumInt(#I1,#I2)
PRINT dbo.DSGetMinimumInt(#V1,#V2)
Test Output:
2010-01-01 00:00:00.000
5
abc
If you are going to use this in a query, I would just use an inline CASE statement, which would be MUCH faster then the UDF:
CASE
WHEN #valueAnyType1<#ValueAnyType2 THEN #valueAnyType1
ELSE #ValueAnyType2
END
you can add protections for NULL if necessary:
CASE
WHEN #valueAnyType1<=ISNULL(#ValueAnyType2,#valueAnyType1) THEN #valueAnyType1
ELSE #ValueAnyType2
END
All major databases except SQL Server support LEAST and GREATEST which do what you want.
In SQL Server, you can emulate it this way:
WITH q (col1, col2) AS
(
SELECT 'test1', 'test2'
UNION ALL
SELECT 'test3', 'test4'
)
SELECT (
SELECT MIN(col)
FROM (
SELECT col1 AS col
UNION ALL
SELECT col2
) qa
)
FROM q
, though it will be a little bit less efficient than a UDF.
Azure SQL DB (and future SQL Server versions) now supports GREATEST/LEAST:
GREATEST
LEAST

Is there a way to make a TSQL variable constant?

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

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