I am creating a SQL query in which I need a conditional where clause.
It should be something like this:
SELECT
DateAppr,
TimeAppr,
TAT,
LaserLTR,
Permit,
LtrPrinter,
JobName,
JobNumber,
JobDesc,
ActQty,
(ActQty-LtrPrinted) AS L,
(ActQty-QtyInserted) AS M,
((ActQty-LtrPrinted)-(ActQty-QtyInserted)) AS N
FROM
[test].[dbo].[MM]
WHERE
DateDropped = 0
--This is where i need the conditional clause
AND CASE
WHEN #JobsOnHold = 1 THEN DateAppr >= 0
ELSE DateAppr != 0
END
The above query is not working. Is this not the correct syntax or is there another way to do this that I don't know?
I don't want to use dynamic SQL, so is there any other way or do I have to use a workaround like using if else and using the same query with different where clauses?
Try this
SELECT
DateAppr,
TimeAppr,
TAT,
LaserLTR,
Permit,
LtrPrinter,
JobName,
JobNumber,
JobDesc,
ActQty,
(ActQty-LtrPrinted) AS L,
(ActQty-QtyInserted) AS M,
((ActQty-LtrPrinted)-(ActQty-QtyInserted)) AS N
FROM
[test].[dbo].[MM]
WHERE
DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) != 1 AND DateAppr != 0)
)
You can read more about conditional WHERE here.
Try this one -
WHERE DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) != 1 AND DateAppr != 0)
)
To answer the underlying question of how to use a CASE expression in the WHERE clause:
First remember that the value of a CASE expression has to have a normal data type value, not a boolean value. It has to be a varchar, or an int, or something. It's the same reason you can't say SELECT Name, 76 = Age FROM [...] and expect to get 'Frank', FALSE in the result set.
Additionally, all expressions in a WHERE clause need to have a boolean value. They can't have a value of a varchar or an int. You can't say WHERE Name; or WHERE 'Frank';. You have to use a comparison operator to make it a boolean expression, so WHERE Name = 'Frank';
That means that the CASE expression must be on one side of a boolean expression. You have to compare the CASE expression to something. It can't stand by itself!
Here:
WHERE
DateDropped = 0
AND CASE
WHEN #JobsOnHold = 1 AND DateAppr >= 0 THEN 'True'
WHEN DateAppr != 0 THEN 'True'
ELSE 'False'
END = 'True'
Notice how in the end the CASE expression on the left will turn the boolean expression into either 'True' = 'True' or 'False' = 'True'.
Note that there's nothing special about 'False' and 'True'. You can use 0 and 1 if you'd rather, too.
You can typically rewrite the CASE expression into boolean expressions we're more familiar with, and that's generally better for performance. However, sometimes is easier or more maintainable to use an existing expression than it is to convert the logic.
The problem with your query is that in CASE expressions, the THEN and ELSE parts have to have an expression that evaluates to a number or a varchar or any other datatype but not to a boolean value.
You just need to use boolean logic (or rather the ternary logic that SQL uses) and rewrite it:
WHERE
DateDropped = 0
AND ( #JobsOnHold = 1 AND DateAppr >= 0
OR (#JobsOnHold <> 1 OR #JobsOnHold IS NULL) AND DateAppr <> 0
)
Often when you use conditional WHERE clauses you end upp with a vastly inefficient query, which is noticeable for large datasets where indexes are used. A great way to optimize the query for different values of your parameter is to make a different execution plan for each value of the parameter. You can achieve this using OPTION (RECOMPILE).
In this example it would probably not make much difference, but say the condition should only be used in one of two cases, then you could notice a big impact.
In this example:
WHERE
DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) <> 1 AND DateAppr <> 0)
)
OPTION (RECOMPILE)
Source Parameter Sniffing, Embedding, and the RECOMPILE Options
This seemed easier to think about where either of two parameters could be passed into a stored procedure. It seems to work:
SELECT *
FROM x
WHERE CONDITION1
AND ((#pol IS NOT NULL AND x.PolicyNo = #pol) OR (#st IS NOT NULL AND x.State = #st))
AND OTHERCONDITIONS
Related
SUM((CASE WHEN ([t2].[__measure__8] > 1) THEN (CASE WHEN [t2].[__measure__8] = 0 THEN NULL ELSE (CAST([t2].[__measure__9] as float) / [t2].[__measure__8]) END) ELSE [t2].[__measure__9] END))
when I use this calculation above Correlated Subquery which has a group by too . Its is taking more than 5 minutes to receive the result set. Moreover, the inner subset of query retrieves in just 4 sec. Am I missing something else?
What is the best way to write this case expression?
Sub case statement looks like unnecessary. You can remove CASE WHEN [t 2].[_ measure _8] = 0
SUM(CASE
WHEN ([t2].[__measure__8] > 1) THEN (CAST([t2].[__measure__9] as float) / [t2].[__measure__8])
ELSE [t2].[__measure__9]
END )
Since you only have 1 condition on your case statement, I suggest to use iif function instead.
sum(
iif([t2].[__measure__8] > 1,
iif([t2].[__measure__8] = 0, null, cast([t2].[__measure__9] as float)/[t2].[__measure__8]),
[t2].[__measure__9])
)
Try to break down your query by using subqueries, remove the sum() first then check the improvements.
I am trying to use the SUBSTR and NVL functions inside the case. The case is in the where clause of the select statement.
The code below gives the following error:
ORA-00905: missing keyword
AND ( CASE
WHEN SUBSTR(upper(p_open_invoice),1,1) = 'Y' THEN
NVL(P.AMOUNT_DUE_REMAINING,0) = 0
ELSE
1=1
END)
This looks like a syntax error around equal operator of NVL function.
That is not how case expressions work (in Oracle) -- there is no boolean type to return.
The simplest method is to remove the `case and express this as simple logic:
AND (SUBSTR(upper(p_open_invoice), 1, 1) <> 'Y' OR
COALESCE(P.AMOUNT_DUE_REMAINING, 0) = 0
)
If p_open_invoice can be NULL, you need to take that into account as well.
You cannot use a collation as a result for case..when statements, it's better converting the condition to
AND (( SUBSTR(upper(p_open_invoice),1,1) = 'Y' AND NVL(P.AMOUNT_DUE_REMAINING,0) = 0 )
OR SUBSTR(upper(p_open_invoice),1,1) != 'Y' )
If you're accustomed to programming in PL/SQL you may have seen that there's a BOOLEAN type in PL/SQL. However, this is not true in the Oracle database itself. The way I usually work around this is to use character expressions which return 'Y' or 'N' instead of TRUE or FALSE.
Keeping this in mind - if you really want to use a CASE expression similar to what you had originally you can use the following:
AND CASE
WHEN SUBSTR(upper(p_open_invoice),1,1) = 'Y'
THEN CASE
WHEN NVL(P.AMOUNT_DUE_REMAINING,0) = 0 THEN 'Y'
ELSE 'N'
END
ELSE 'Y'
END = 'Y'
Here the CASE expression returns either 'Y' or 'N', which is then compared with 'Y'.
So I have EXISTS in huge query which looks like this:
EXISTS(
SELECT
*
FROM
ExistTable
WHERE
ExTableFieldA = #SomeGuid AND
ExTableFieldB = MainTableFieldB AND
ExTableFieldA <> (
CASE
WHEN MainTableFieldZ = 10 THEN MainTableFieldYYY
ELSE NULL
END
)
)
The problem comes from ELSE part of CASE statement, this ExTableFieldA <> NULL will be always false. I could easily write another parameter #EmptyGuid and make it equal to '00000000-0000-0000-0000-000000000000' and everything will work but is this the best approach ?
Pretty much I want to execute another check into the exist for the small size of the records which return the "main" query.
How about removing the case and just using boolean logic?
WHERE ExTableFieldA = #SomeGuid AND
ExTableFieldB = MainTableFieldB AND
(MainTableFieldZ <> 10 OR ExTableFieldA <> MainTableFieldYYY)
I would also recommend that you qualify the column names by including the table alias.
Note: This does assume that MainTableFieldZ is not NULL. If that is a possibility than that logic can easily be incorporated.
ELSE NULL is implied even if you don't list it, but you could use ISNULL here.
ISNULL(ExTableFieldA,'') <> (
CASE
WHEN MainTableFieldZ = 10 THEN MainTableFieldYYY
ELSE ''
END
)
You may need to use some other value like 9999 instead of ''
I'm trying to use the following logical expression as part of a stored procedure for Microsoft SQL Server 2012, where #filter1 and #filter2 are of type bit (i.e. boolean).
((#filter1 <> 0) = (T.ID = '123')) and
((#filter2 <> 0) or (T.FK is null))
I get a syntax error at the first =. Evidently results of boolean terms can be combined using AND and OR but cannot be checked for equality with other such terms.
Is this indeed the case and if so, how would one normall reformulate such a condition for this SQL environment? Do I have to compare something like case when TERM then 1 else 0 end?
If memory serves me right you can't evaluate the assignment operation as a boolean value (in the way you can in C for instance) so I think you would have to do this:
((#filter1) = (case when T.ID = '123' then 1 end)) and
((#filter2 <> 0) or (T.FK is null))
This should work.
(((#filter1 <> 0) AND (T.ID = '123')) OR ((#Filter1 = 0) AND (t.ID <> '123'))) and
((#filter2 <> 0) or (T.FK is null))
I am creating a SQL query in which I need a conditional where clause.
It should be something like this:
SELECT
DateAppr,
TimeAppr,
TAT,
LaserLTR,
Permit,
LtrPrinter,
JobName,
JobNumber,
JobDesc,
ActQty,
(ActQty-LtrPrinted) AS L,
(ActQty-QtyInserted) AS M,
((ActQty-LtrPrinted)-(ActQty-QtyInserted)) AS N
FROM
[test].[dbo].[MM]
WHERE
DateDropped = 0
--This is where i need the conditional clause
AND CASE
WHEN #JobsOnHold = 1 THEN DateAppr >= 0
ELSE DateAppr != 0
END
The above query is not working. Is this not the correct syntax or is there another way to do this that I don't know?
I don't want to use dynamic SQL, so is there any other way or do I have to use a workaround like using if else and using the same query with different where clauses?
Try this
SELECT
DateAppr,
TimeAppr,
TAT,
LaserLTR,
Permit,
LtrPrinter,
JobName,
JobNumber,
JobDesc,
ActQty,
(ActQty-LtrPrinted) AS L,
(ActQty-QtyInserted) AS M,
((ActQty-LtrPrinted)-(ActQty-QtyInserted)) AS N
FROM
[test].[dbo].[MM]
WHERE
DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) != 1 AND DateAppr != 0)
)
You can read more about conditional WHERE here.
Try this one -
WHERE DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) != 1 AND DateAppr != 0)
)
To answer the underlying question of how to use a CASE expression in the WHERE clause:
First remember that the value of a CASE expression has to have a normal data type value, not a boolean value. It has to be a varchar, or an int, or something. It's the same reason you can't say SELECT Name, 76 = Age FROM [...] and expect to get 'Frank', FALSE in the result set.
Additionally, all expressions in a WHERE clause need to have a boolean value. They can't have a value of a varchar or an int. You can't say WHERE Name; or WHERE 'Frank';. You have to use a comparison operator to make it a boolean expression, so WHERE Name = 'Frank';
That means that the CASE expression must be on one side of a boolean expression. You have to compare the CASE expression to something. It can't stand by itself!
Here:
WHERE
DateDropped = 0
AND CASE
WHEN #JobsOnHold = 1 AND DateAppr >= 0 THEN 'True'
WHEN DateAppr != 0 THEN 'True'
ELSE 'False'
END = 'True'
Notice how in the end the CASE expression on the left will turn the boolean expression into either 'True' = 'True' or 'False' = 'True'.
Note that there's nothing special about 'False' and 'True'. You can use 0 and 1 if you'd rather, too.
You can typically rewrite the CASE expression into boolean expressions we're more familiar with, and that's generally better for performance. However, sometimes is easier or more maintainable to use an existing expression than it is to convert the logic.
The problem with your query is that in CASE expressions, the THEN and ELSE parts have to have an expression that evaluates to a number or a varchar or any other datatype but not to a boolean value.
You just need to use boolean logic (or rather the ternary logic that SQL uses) and rewrite it:
WHERE
DateDropped = 0
AND ( #JobsOnHold = 1 AND DateAppr >= 0
OR (#JobsOnHold <> 1 OR #JobsOnHold IS NULL) AND DateAppr <> 0
)
Often when you use conditional WHERE clauses you end upp with a vastly inefficient query, which is noticeable for large datasets where indexes are used. A great way to optimize the query for different values of your parameter is to make a different execution plan for each value of the parameter. You can achieve this using OPTION (RECOMPILE).
In this example it would probably not make much difference, but say the condition should only be used in one of two cases, then you could notice a big impact.
In this example:
WHERE
DateDropped = 0
AND (
(ISNULL(#JobsOnHold, 0) = 1 AND DateAppr >= 0)
OR
(ISNULL(#JobsOnHold, 0) <> 1 AND DateAppr <> 0)
)
OPTION (RECOMPILE)
Source Parameter Sniffing, Embedding, and the RECOMPILE Options
This seemed easier to think about where either of two parameters could be passed into a stored procedure. It seems to work:
SELECT *
FROM x
WHERE CONDITION1
AND ((#pol IS NOT NULL AND x.PolicyNo = #pol) OR (#st IS NOT NULL AND x.State = #st))
AND OTHERCONDITIONS