I need help with this check constraint, I get the following error message: "Msg 102, Level 15, State 1, Line 14
Incorrect syntax near '='."
Or maybe the question I should ask is if this is possible using a check constraint
What I am trying to achieve is: If InformationRestricted is True, InformationNotRestricted cannot be true and InformationRestrictedFromLevel1, InformationRestrictedFromLevel2, InformationRestrictedFromLevel3, InformationRestrictedFromLevel4, InformationRestrictedFromLevel5 cannot be true
I am not trying to assign values to the columns, just trying to ensure the values of the columns = 0 (i.e. false) if InformationRestricted is True
Here is the script:
CREATE TABLE EmployeeData
(FirstName varchar(50),
Last Name varchar(50),
Age int,
Address varchar(100),
InformationRestricted bit,
InformationNotRestricted bit,
InformationRestrictedFromLevel1 bit,
InformationRestrictedFromLevel2 bit
InformationRestrictedFromLevel3 bit
InformationRestrictedFromLevel4 bit
InformationRestrictedFromLevel5 bit);
ALTER TABLE EmployeeData ADD CONSTRAINT ck_EmployeeData
CHECK (CASE WHEN InformationRestricted = 1 THEN InformationNotRestricted = 0 --InformationRestricted is true, InformationNotRestricted is false
AND( InformationRestrictedFromLevel1 = 0 --is false
OR InformationRestrictedFromLevel2 = 0 --is false
OR InformationRestrictedFromLevel3 = 0 --is false
OR InformationRestrictedFromLevel4 = 0 --is false
OR InformationRestrictedFromLevel5 = 0)); --is false
A CASE expression is something that returns a value of a particular data type (the type to be determined by the various datatypes of each THEN clause).
SQL Server doesn't have a boolean data type, so you can't return the result of a comparison operation.
Try adding additional comparisons into WHEN clauses, and having the THENs return either 1 or 0, if you want to allow or disallow the outcome (respectively). Then compare the overall result to 1.
I can't parse out the sense of your condition entirely, but something like:
CHECK(CASE WHEN InformationRestricted = 1 THEN
CASE WHEN InformationNotRestricted = 0 AND
(InformationRestrictedFromLevel1 = 0 --is false
OR InformationRestrictedFromLevel2 = 0 --is false
OR InformationRestrictedFromLevel3 = 0 --is false
OR InformationRestrictedFromLevel4 = 0 --is false
OR InformationRestrictedFromLevel5 = 0)
THEN 1
ELSE 0
END
--Other conditions?
END = 1)
My confusion is I'd have though you'd want to check that one and only one of the InformationRestrictedFromXXX columns would be one. In fact, from the general description, (without knowing more about your problem domain), I'd have probably just created a column InformationRestrictionLevel, of type int, with 0 meaning unrestricted, and higher values indicating the level it's restricted from.
Looks like you're not closing the case with end. The basic format of a check constraint using case is:
check(case when <condition> then 1 else 0 end = 1)
If you nest multiple cases, be sure to match the number of cases with the number of ends:
check
(
1 =
case
when <condition> then
case
when <condition> then 1
else 0
end
else 0
end
)
Formatting all elements of the same case with the same indentation can be a big help.
Related
I need to compare variable in case condition in stored procedure.
case when #column <> 0 then ...
ELSE 0 END
but whenever am getting #column as NULL, then the above script returning as 0.
will sql consider both 0 & NULL as same.
Am using sql server 2014.
Thanks All
No. SQL considers NULL as "I have no idea". Comparing anything with "I have no idea" results in an answer of "I totally have no idea". Look:
- How high is John?
- I have no idea.
- What is two centimeters higher than John?
- I have no idea.
Even comparison between two NULL values is not true: if I have no idea how tall John is and if I also have no idea how tall Jack is, I can't conclude that John is equally tall as Jack (and I can't conclude that John is not equally tall as Jack). The only sensible answer is... "I have no idea".
The way to test for NULL is with IS operator, which specifically exists for this scenario (e.g. #column IS NULL, or #column IS NOT NULL).
So NULL is not equal to 0, nor is it NOT equal to 0. The result of NULL <> 0 is NULL. However, NULL is falsy where conditionals are concerned, so CASE thinks you should get the ELSE branch any time #column is NULL.
In case if you want to execute the then part of case if the column value is null, then modify your condition to check for nulls also
CASE WHEN (#column <> 0 OR #column IS NULL) then ...
ELSE 0 END
I have a general question for when you are using a CASE statement in SQL (Server 2008), and more than one of your WHEN conditions are true but the resulting flag is to be different.
This is hypothetical example but may be transferable when applying checks across multiple columns to classify data in rows. The output of the code below is dependant on how the cases are ordered, as both are true.
DECLARE #TESTSTRING varchar(5)
SET #TESTSTRING = 'hello'
SELECT CASE
WHEN #TESTSTRING = 'hello' THEN '0'
WHEN #TESTSTRING <> 'hi' THEN '1'
ELSE 'N/A'
END AS [Output]
In general, would it be considered bad practice to create flags in this way? Would a WHERE, OR statement be better?
Case statements are guaranteed to be evaluated in the order they are written. The first matching value is used. So, for your example, the value 0 would be returned.
This is clearly described in the documentation:
Searched CASE expression:
Evaluates, in the order specified, Boolean_expression for each WHEN clause.
Returns result_expression of the first Boolean_expression that evaluates to TRUE.
If no Boolean_expression evaluates to TRUE, the Database Engine returns the else_result_expression if an ELSE clause is specified, or
a NULL value if no ELSE clause is specified.
As for whether this is good or bad practice, I would lean on the side of neutrality. This is ANSI behavior so you can depend on it, and in some cases it is quite useful:
select (case when val < 10 then 'Less than 10'
when val < 100 then 'Between 10 and 100'
when val < 1000 then 'Between 100 and 1000'
else 'More than 1000' -- or NULL
end) as MyGroup
To conclude further - SQL will stop reading the rest of the of the case/when statement when one of the WHEN clauses is TRUE. Example:
SELECT
CASE
WHEN 3 = 3 THEN 3
WHEN 4 = 4 THEN 4
ELSE NULL
END AS test
This statement returns 3 since this is the first WHEN clause to return a TRUE, even though the following statement is also a TRUE.
I have a stored procedure that is calculating the number of documents I have that are not in complete (1000) or canceled (1100). When I have just one of those conditionals it counts the number correctly but once I add the or, it simply grabs everything ignoring any of the logic. There must be some fundamental thing i'm missing with SQL here
SELECT
[PartnerCoId] as DisplayID
,[PartnerCompanyName] as DisplayName
,Count(*) as DocumentTotal
FROM vwDocuments
where coid = #inputCoid and DocumentType = 'order'
and Status <> 1100
and PartnerCoId <> #inputCoid
group by
[PartnerCoId]
,[PartnerCompanyName]
union all
SELECT [CoId] as DisplayID
,[CompanyName] as DisplayName
,Count(*) as DocumentTotal
FROM vwDocuments
where PartnerCoId = #inputCoid and DocumentType = 'order'
and Status <> 1100
and CoId <> #inputCoid
group by [CoId]
,[CompanyName]
order by [DisplayName]
This will return the number of documents not in canceled status. If I change the 1100 to 1000 it returns the number of documents not in complete status. Once I update the query to:
and (Status <> 1100 or Status <> 1000)
It breaks the logic.
Thoughts? I have tried quite a number of different combinations of query logic and cannot straighten this out.
Rather than wrestle with boolean logic, use not in:
and Status not in (1100, 1000)
It's easier to read and understand, because it's practically English, and because it's all in one statement you don't need brackets around it either.
If I understand you correctly, you want everything where Status is neither 1100 nor 1000.
If so, then you need this:
and (Status <> 1100 and Status <> 1000)
If you use or, then a Status of 1100 will pass the test because it is <> 1000.
I think your logic may be a little bit off. Saying (NOT complete or NOT cancelled) will return all of your documents because all rows will fit this criteria.
Take a document with status of 1100. This will be returned in the query because it evaluates to TRUE on half of the OR statement.
Try replacing that line with
AND Status NOT IN (1000,1100)
This should return only documents that are neither completed or cancelled. Hope this helps!
Let's simplify and think about your logic.
DECLARE #i INT = 1;
IF (#i <> 1 OR #i <> 2)
PRINT 'true';
ELSE
PRINT 'false';
Can you provide a value for #i that generates false? I can't think of one. Think about it:
if #i = 1, then #i <> 1 is false, but #i <> 2 is true. Since only one of these conditions has to be true for the whole condition to be true, the result is true.
if #i = 2, then #i <> 1 is true, but #i <> 2 is false. Since only one of these conditions has to be true for the whole condition to be true, the result is true.
if #i is any other value outside of 1 and 2, then both conditions are true.
As the other answers demonstrate, the way to fix this is to change OR to AND, or use NOT IN (though I like NOT IN less because when you are checking a column, and the column is NULLable, the results surprise and confuse most people - and I prefer to program consistently instead of having to be aware of the cases where something works and the cases where it really, really doesn't).
Since the following code prints 'First' and 'Second' INSERT that order, can I conclude that the first condition satisfied is ALWAYS executed?
DECLARE #Constant1 int = 1
DECLARE #Constant2 int = 2
select
case
when #Constant1 = 1
then 'First'
when #Constant1 = 1 and #Constant2 = 2
then 'Second'
end as Result
select
case
when #Constant1 = 1 and #Constant2 = 2
then 'Second'
when #Constant1 = 1
then 'First'
end as Result
I know that sometimes parallel processing effects the outcome and I was trying to understand IF this type of situation that I see in Production would always return the same result.
This question is intended to understand if there is a potential issue in production code. If I were going to write the code anew, I think I would try to make the code explicitly mutually exclusive..
select
case
when #Constant1 = 1 and #Constant2 != 2
then 'First'
when #Constant1 = 1 and #Constant2 = 2
then 'Second'
end as Result
The Documentation for CASE states.
Searched CASE expression:
Evaluates, in the order specified, Boolean_expression for each WHEN clause.
Returns result_expression of the first Boolean_expression that evaluates to TRUE.
If no Boolean_expression evaluates to TRUE, the Database Engine returns the else_result_expression if an ELSE clause is specified, or
a NULL value if no ELSE clause is specified.
So it will return the first true branch.
For a simple query such as in the question I would expect it to not evaluate the other branches either.
A few cases where this short circuiting behaviour does not work as expected/advertised are discussed in this DBA site question.
Does SQL Server read all of a COALESCE function even if the first argument is not NULL?
But just to be clear these issues do not affect the left to right precedence order of the result (except for the case when evaluating a later branch causes an error to occur such that no result is returned at all)
I would like to use AND/OR between the conditions in a stored procedure, and the decision is dependent on the parameter value whether it was 0 (AND) or 1 (OR)
Can anyone help me with this please, i guess this is an easy thing to do but i can't seem to figure it out. Thanks
The easiest way (on first glance) would be to concatenate the query string using dynamic SQL, but dynamic SQL has its issues.
See The Curse and Blessings of Dynamic SQL for an in-depth explanation.
So I would try to avoid dynamic SQL, which is no big deal if your queries are not too complex.
The easiest way is just to fire two different queries depending on the parameter value:
CREATE PROCEDURE spTest
#AndOr bit
AS
BEGIN
if #AndOr = 0 begin
select * from YourTable where foo = 1 and bar = 2
end
else begin
select * from YourTable where foo = 1 or bar = 2
end
END
This is of course an example with a very simple query.
If you have lots of queries, or if your queries are very complex, this might not be the best solution because it forces you to duplicate all queries...but as always, it depends :-)
You can implement your logic on a CASE statement. Something like this:
CREATE PROCEDURE dbo.MySP #OrAnd BIT
AS
BEGIN
SELECT *
FROM MyTable
WHERE CASE WHEN Condition1 AND Condition2 AND #OrAnd = 0 THEN 1
WHEN (Condition1 OR Condition2) AND #OrAnd = 1 THEN 1 ELSE 0 END = 1
END
If you convert the simple conditions' boolean results into numeric ones (0 or 1), you will be able to use your parameter in the following way:
(
(CASE WHEN condition1 THEN 1 ELSE 0 END ^ #AndOr)
&
(CASE WHEN condition2 THEN 1 ELSE 0 END ^ #AndOr)
) ^ #AndOr = 1
Here #AndOr is your parameter, ^ is the Transact-SQL bitwise exclusive OR operator, & stands for the bitwise AND in Transact-SQL, and the CASE expressions are used to convert the boolean results into 0 or 1.
If #AndOr = 0 (which means we want AND between the conditions), the above expression effectively boils down to this:
case1 & case2 = 1
because X XOR 0 yields X and so neither individual values of case1 and case2 nor the entire result of the & operator are not affected by the ^ operators. So, when #AndOr is 0, the result of the original expression would be equivalent to the result of condition1 AND condition2.
Now, if #AndOr = 1 (i.e. OR), then every ^ operator in the expression returns the inverted value of its left operand, in other words, negates the left operand, since 1 XOR 1 = 0 and 0 XOR 1 = 1. Therefore, the original expression would essentially be equivalent to the following:
¬ (¬ case1 & ¬ case2) = 1
where ¬ means negation. Or, converting it back to the booleans, it would be this:
NOT (NOT condition1 AND NOT condition2)
According to one of De Morgan's laws,
(NOT A) AND (NOT B) = NOT (A OR B)
Applying it to the above condition, we get:
NOT (NOT condition1 AND NOT condition2) = NOT (NOT (condition1 OR condition2)) =
= condition1 OR condition2
So, when #AndOr is 1, the expression given in the beginning of my answer is equivalent to condition1 OR condition2. Thus, it works like expected based on the value of #AndOr.
Having the input parameter you can use a IF clause to make different selects.
If input parameter = 0 make the AND conditions, otherwise make the OR conditions.
I can't see any particular elegant way to do it. So here's the straightforward approach
create function myfun (#parm1 int, #parm2 int, #andor int) returns int
begin
if (#andor = 0 AND #parm1 = 99 AND #parm2 = 99) return 1
else if (#andor = 1 AND (#parm1 = 99 OR #parm2 = 99)) return 1
return 0
end
go
select dbo.myfun(99,98,0) -- AND condition should return 0
select dbo.myfun(99,98,1) -- OR condition should return 1
select dbo.myfun(98,98,0) -- AND condition should return 0
select dbo.myfun(98,98,1) -- OR condition shoujld return 0