I have two params that are passed in a function which passed down to the SQL string. Variables can be null or has a value (int). If x is not null, use "this" column else use "that" column. I'm using SQL Server.
// Inside a function with two variables passed, x and y
$sql = "
SELECT
[...]
FROM
[...]
WHERE
[...]
AND [...]
-- This is the tricky part
AND
--- if $x is not null, use foo column else use bar column
IF (x, R.column = 2, R.another_column = 3)
[...]
";
Is this possible to select a column based on the value of the variable passed in?
AND
(
($x is not null and R.column = 2) OR
($x is null and R.another_column = 3)
)
Unless I'm misunderstanding, you just need logic, or a case statement would work.
$sql = "
SELECT
[...]
FROM
[...]
WHERE
[...]
AND
[...]
-- This is the tricky part
AND
--- if $x is not null, use foo column else use bar column
-- IF (x, R.column = 2, R.another_column = 3)
(
(X IS NULL AND R.column = 2)
OR
(X IS NOT NULL AND R.another_column = 3)
)
";
AND
--- if $x is not null, use foo column else use bar column
case
when x is NULL then R.another_column = 3
else R.column = 2
end
--in SQL Server...
DECLARE #x INT = 3;
SELECT *
FROM sys.schemas
WHERE (#x IS NULL AND schema_id = 2)
OR (#x IS NOT NULL and schema_id = 3)
--optional depending on how much you execute this query, it may help
OPTION(RECOMPILE)
Related
I'm trying to execute a raw query in Django where I dynamically want to pick column names.
Eg
def func(all=True){
if all:
query_parameters = {
'col': '*'
}
else:
query_parameters = {
'col': 'a,b,c'
}
with connections["redshift"].cursor() as cursor:
cursor.execute(
"select %(col)s from table limit 2 ;",
query_parameters,
)
val = dictfetchall(cursor)
return val
}
Django is executing it like.
select "*" from table limit 2;
so the output is just like select "*"
*
and in the else case it is executed like
select "a,b,c" from table limit 2;
so the output is a,b,c
How can I run the command so that Django run it like
select a , b , c from table limit 2
so that the output is
a b c
1 2 3
4 5 6
I found a hack myself.
See Here
Explanation
Prepared query step by step
Input data (Columns I need)
self.export_col = “a,b,c”
def calc_col(self):
if self.exp == 'T':
select_col = ""
self.export_col = self.export_col.split(',')
for col in self.export_col:
select_col += col + ","
select_col = select_col[:-1]
self.export_col = select_col
else:
self.export_col += '*'
def prepare_query(self):
query += " SELECT "
query += self.export_col
query += """ from table limit 2;"""
I have a desktop application that I am converting to web and I am having trouble understanding the purpose of the IsNull parts of the query. The query is for Ms SQL and I know it has a IsNull function but this is not it. So I'm confused as to it's purpose. Below is my query:
UPDATE tb_category
SET
Email = #Email,
CandidateID = #CandidateID,
Code = #Code,
TestDate = #TestDate,
Description = #Description,
PointsEarned = #PointsEarned,
PointsAvailable = #PointsAvailable,
Average25th = #Average25th,
Average75th = #Average75th,
ImportedDate = #ImportedDate,
CreationDate = #CreationDate,
TestNum = #TestNum,
CategoryNum = #CategoryNum
WHERE ((Email = #Original_Email)
AND (CandidateID = #Original_CandidateID)
AND (Code = #Original_Code)
AND (TestDate = #Original_TestDate)
AND ((#IsNull_Description = 1 AND Description IS NULL) OR (Description = #Original_Description))
AND (PointsEarned = #Original_PointsEarned)
AND ((#IsNull_PointsAvailable = 1 AND PointsAvailable IS NULL) OR (PointsAvailable =
#Original_PointsAvailable))
AND ((#IsNull_Average25th = 1 AND Average25th IS NULL) OR (Average25th = #Original_Average25th))
AND ((#IsNull_Average75th = 1 AND Average75th IS NULL) OR (Average75th = #Original_Average75th))
AND ((#IsNull_ImportedDate = 1 AND ImportedDate IS NULL) OR (ImportedDate = #Original_ImportedDate))
AND ((#IsNull_CreationDate = 1 AND CreationDate IS NULL) OR (CreationDate = #Original_CreationDate))
AND (TestNum = #Original_TestNum)
AND (CategoryNum = #Original_CategoryNum));
I tried simplifying the update statement by removing the IsNull sections but that did not work.
In SQL null is not equal (=) to anything—not even to another null, so in your query in case if both values are null (old and new one) you need to take that into account and check values with IS NULL.
I'm seeing this pattern repeated several times in the WHERE clause:
#IsNull_Description = 1 AND Description IS NULL
It means that a variable, #IsNull_SomeColumnName, which is presumably set earlier in the code, has a value of 1, and the column that the variable relates to is currently NULL.
The function IsNull(Param1, Param2) is used to substitute the value of the second parameter for the value of the first parameter if the first parameter IS NULL, and the function returns the value of Param2.
In SQL Server, and quite a few other RDBMSs, the IS NULL syntax is used to check if a value is currently NULL. Here, Description IS NULL will return TRUE if, well, Description is null, and FALSE if it is not.
I have, as a part of a bigger query, some subqueries that I would like to convert to CASE statements instead.
The subquery looks like this (and works):
(SELECT (((SUM(DAm)-(SUM(StcCst)*-1))*100)/NULLIF(SUM(DAm),0)) AS 'DG' FROM [F0001].[dbo].[ProdTr] WHERE AcYrPr = '201601' AND ProdTr.TrTp = 1 AND [F0001].[dbo].[ProdTr].CustNo = '12773') AS dg_period_1
However, I don't seem to find any logical way to put this into a CASE-statement.
Any help would be appreciated!
(
SELECT CASE
WHEN SUM(t1.DAm) <> 0
THEN (SUM(t1.DAm) + SUM(t1.StcCst)) * 100 / SUM(t1.DAm)
ELSE 0 /* or whatever you want to have in this case */
END AS 'DG'
FROM [F0001].[dbo].[ProdTr] t1
WHERE t1.AcYrPr = '201601' AND
t1.TrTp = 1 AND
t1.CustNo = '12773'
) AS dg_period_1
I also removed some unneeded parentheses and simplified an operation (x - (y * -1) = x + y)
You could use the following statement with CASE provided you want to return a null when SUM(DAm) is null or 0.
(SELECT CASE
WHEN SUM(DAm) IS NOT NULL and SUM(DAm) <> 0 THEN (((SUM(DAm) - (SUM(StcCst) * -1)) * 100) /SUM(DAm))
ELSE NULL
END AS 'DG'
FROM [F0001].[dbo].[ProdTr]
WHERE AcYrPr = '201601'
AND ProdTr.TrTp = 1
AND [F0001].[dbo].[ProdTr].CustNo = '12773') AS dg_period_1
MY QUERY IS
DECLARE #AutoApprove BIT
SET #AutoApprove = (
SELECT AutoApprove
FROM dbo.CommentBox_Setting
WHERE UserModuleID = #myModuleID
AND PortalID = #portalID
AND CultureCode = #cultureCode
)
From this i will get whether 1 OR 0 (TRUE OR FALSE) furthermore i have
SELECT * FROM ComentBox_Comment
WHERE UpperModuleID = #UpperModuleID
AND ModuleID = #myModuleID
AND portalID = #portalID
AND cultureCode = #cultureCode
AND //Here i need to check condition
(IF(#AutoApprove=0){ THEN isapprove=1}else {do not check})
Note here isapprove is table filedName
I know ,i can do this with long query i need short and easy way.
Help me out.
Try something like
AND CASE WHEN #AutoApprove=0 THEN isapprove ELSE 1 END = 1
This will check isapprove = 1 if #AutoApprove = 0, or 1=1(ignore) otherwise.
CASE (Transact-SQL)
Is there a way to do this shorter, for instance using some sort of conditional operator in Transact-sql?
IF #ParentBinaryAssetStructureId = -1
BEGIN
SET #ParentBinaryAssetStructureId = NULL
END
UPDATE BinaryAssets.BinaryAssetStructures
SET ParentBinaryAssetStructureId = #ParentBinaryAssetStructureId
WHERE BinaryAssetStructureId = #OriginalBinaryAssetStructureId
USE NULLIF()
UPDATE BinaryAssets.BinaryAssetStructures
SET ParentBinaryAssetStructureId = NULLIF(#ParentBinaryAssetStructureId,-1)
WHERE BinaryAssetStructureId = #OriginalBinaryAssetStructureId
The ternary (conditional) operator in c like languages:
x = doSomething ? 5 : 7
would be written like this in SQL:
SELECT #x = CASE WHEN #doSomething = 1 THEN 5 ELSE 0 END
There can be multiple cases (when clauses):
SELECT #x = CASE WHEN #doSomething = 1 THEN 5 WHEN #somethingElse = 1 THEN 20 ELSE 0 END
UPDATE BinaryAssets.BinaryAssetStructures
SET ParentBinaryAssetStructureId =
CASE ParentBinaryAssetStructureId
WHEN -1 THEN NULL
ELSE ParentBinaryAssetStructureId
END
WHERE BinaryAssetStructureId = #OriginalBinaryAssetStructureId
Give that a whirl