Alternative to relying on execution order of conditions in SQL 'where' clause - sql

In languages such as JavaScript you can have 2 conditional statements and "protect" the second one with the first one. For instance:
if( scarryObject != null && scarryObject.scarryMethod() ) { ... }
// if scarryObject is null scarryMethod will not be called
I thought I would achieve the same in SQL like so:
where int_date > 19500101
and month(CONVERT(smalldatetime, ... int_date))
The problem here is that if int_date is some "bad" value like -1, 0, 1 the conversion will fail and the sp will stop with an error. I thought the first check int_date > 19500101 would get evaluated first and if false the second condition would be skipped.
It seems like it does not work like this... or? Is there any other way of doing this?
Thanks!


Your query is syntactically not correct, as the clausemonth(CONVERT.... is not a condition.
Let's assume you want to compare with a certain number, a possible way of expressing what you want would be
SELECT *
FROM myTable
WHERE case
when int_date > 19500101
then -1
else month(CONVERT(smalldatetime, ... int_date))
end = #YourMonth
You would 'protect' the evaluation of the 'month' and not the condition.


You could try splitting the query into two. Here is the concept:
SELECT *
FROM (
SELECT *
FROM myTable
WHERE int_date > 19500101
) t
WHERE month(CONVERT(smalldatetime, ... t.int_date))

Related

Where statement in my query is supposed to return only today's and yesterday's dates, but is still returning earlier dates

I am looking to only retrieve data from the past 24 hours. The WHERE statement I am using, in theory, should retrieve only from those productiondates. However, I am still having week-old productiondates returned. Any thoughts on how to improve this, or am I doing it wrong? I am using periscope.
select example1,
example2,
example3,
productiondate,
example4,
example5
from final
where exampleX = exampleY or exampleX is null
and productiondate > DATEADD(day,-1, GETDATE())
and example1 <> 'XXX'
and example2 <> 'YYY'
and example2 <> 'ZZZ'
order by 2

Logical operator precedence in SQL can be surprising. You need parentheses around the OR.
where (exampleX = exampleY or exampleX is null)
Alternatively, you could do this:
where coalesce(exampleX, exampleY) = exampleY

CASE in WHERE clause returns Error

I'm running this code:
SELECT hID
FROM logonsHistory
WHERE aIDs NOT LIKE '%''101''%' AND
CASE src
WHEN 0 THEN
uID IN(29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481)
END
I get this error:
Incorrect syntax near the keyword 'IN'
I have no idea what's wrong.

A CASE statement is not appropriate in this case. Just use a simple OR condition:
SELECT hID
FROM logonsHistory
WHERE aIDs NOT LIKE '%''101''%'
AND (
src <> 0 -- add a COALESCE here if src can be NULL
OR uID IN(29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481)
)
... which basically is the equivalent of only applying the uID filtering if src = 0, which is what you appeared to be trying to accomplish with your query.

It sounds like you don't have to use CASE please test this
SELECT hID
FROM logonsHistory
WHERE aIDs NOT LIKE '%''101''%'
AND ( (src = 0 --scr is 0 => must have uid in the list
AND UID IN (29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481))
OR src <> 0) --else src is not 0 and there is no additional condition
i have a doubt on your not like condition have you tested it alone?

Guess this is what you are looking for
WHERE aIDs NOT LIKE '%''101''%' or
(
src = 0
AND
uID IN(29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481
)

It looks like your statement is not formatted properly. you placed a condition rather than a value to set within "When 0 then ...... END
the uID IN(29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481) you have there is a condition and shouldn't have been there

The when part of a case statement should select a single value. what you are trying to do is to check for a condition.
Or if you are checking for uid in those values, you should do
case when src = 0 then
case when uID IN (29,41,42,45,49,50,57,73,83,107,166,349,356,367,375,376,416,471,472,473,474,481)
then 'It is a Client ID'
-- add another when or else part here if required
end
else 'Not a UID and not a Client ID'
end

Conditional Where clauses in JasperReports

Let's say I want a JasperReport that lets the user filter on a date if they so wish. The SQL is as follows:
select * from foo where bar = $P{bar} and some_date > $P{some.date}
Now, I don't want to filter by some date if they didn't pass the date in. I found the following kludge that people use:
select * from foo where bar = $P{bar} $P!{some.date.fragment}
And the some.date.fragment parameter is defined with the following default:
($P{some.date} == null || $P{some.date}.equals("")) ? "" : "AND some_date >'" + new java.sql.Date($P{some.date}.getTime()).toString() + "'"
This is not working as the toString doesn't output the date in a format that my SQL server understands. I would like to have the conditional still use a prepared statement with the jdbc driver and toss the parameter in, I just want the prepared statement to be dependent on if the parameter is null or not. Can this be done?

Before you have used the $P!{} expression the JDBC-Driver does all formatting for you.
But if you use the $P!{} expression you have to format yourself.
Something like this should work:
(
$P{some.date} == null
?
""
:
"AND some_date >'" + (new SimpleDateFormat("dd.MM.yyyy HH:mm:ss.SSS")).format($P{some.date}) + "'"
)
Depending on your data type you have to customize dd.MM.yyyy HH:mm:ss.SSS.
If you don't want to use the $P!{} expression you can avoid it with the solution below.
I personally don't like this way. It also may cause a bad execution plan.
If don't want to use $P!{} because you worry about sql injection. It's needless as long your parameter $P{some.date} contains a safe data type like java.lang.Date.
Create a parameter. Let's call it ${is_null_pram} and add a default expression with param class Integer:
($P{some.date} == null ? 1 : 0)
Now you can query:
SELECT
*
FROM foo
WHERE
bar = $P{bar}
AND
(
some_date > $P{some.date}
OR 1 = $P{is_null_pram}
)

I think you can use the function:
$X{EQUAL, <column_name>, <parameter_name>}
It optimizes the query as you can see in this help page.

You can use this conditional statement
select *
from foo
where bar = $P{bar} and some_date > $P{some.date} or $P{some.date} is null

How to select if a row exists in HQL

EDIT: Specifically talking about querying against no table. Yes I can use exists, but I'd have to do
select case when exists (blah) then 1 else 0 end as conditionTrue
from ARealTableReturningMultipleRows
In T-SQL I can do:
select case when exists(blah) then 1 else 0 end as conditionTrue
In Oracle I can do:
select case when exists(blah) then 1 else 0 end as conditionTrue from DUAL
How can I achieve the same thing in HQL?
select count() seems like the second-best alternative, but I don't want to have to process every row in the table if I don't need to.

Short answer: I believe it's NOT possible.
My reasoning:
According to Where can I find a list of all HQL keywords? Hibernate project doesn't publish HQL grammar on their website, it's available in the Hibernate full distribution as a .g ANTLR file though.
I don't have much experience with .g files from ANTLR, but you can find this in the file (hibernate-distribution-3.6.1.Final/project/core/src/main/antlr/hql.g):
selectFrom!
: (s:selectClause)? (f:fromClause)? {
// If there was no FROM clause and this is a filter query, create a from clause. Otherwise, throw
// an exception because non-filter queries must have a FROM clause.
if (#f == null) {
if (filter) {
#f = #([FROM,"{filter-implied FROM}"]);
}
else
throw new SemanticException("FROM expected (non-filter queries must contain a FROM clause)");
}
which clearly states there are some HQL queries having no FROM clause, but that's acceptable if that's a filter query. Now again, I am not an expert in HQL/Hibernate, but I believe a filter query is not a full query but something you define using session.createFilter (see How do I turn item ordering HQL into a filter query?), so that makes me think there's no way to omit the FROM clause.

I'm use fake table with one row for example MyDual.
select case when exists(blah) then 1 else 0 end as conditionTrue from MyDual

According to http://docs.jboss.org/hibernate/core/3.3/reference/en/html/queryhql.html#queryhql-expressions it looks like they support both case and exists statements.

No Result Returned From SQL Query

I am running the following query, but no rows are returned even though a record exists that should match the query.
SELECT
*
FROM
tblsignup
WHERE
usr_email='amir#gmail.com'
AND
(status=1 or status=2)

You should try by simplifying the query (yeah...even if it's so simple)
try this
Select * from tblsignup
then
Select * from tblsignup where
usr_email = 'amir#gmail.com'
then
Select * from tblsignup where
usr_email='amir#gmail.com' and
status > 0
//I know you won't use > 0 at the end, but we want to eliminate the most cause of error we simplify by > 0 only to be easier to read
Tell us from where you start getting 0 line, this could lead us to the problem, I know I already had a problem like that with a field named "date", because date is already used by MySQL, funny MySQL still let me use that fieldname tho.

Try this:
select * from `tblsignup` where `usr_email`='amir#gmail.com' and (`status`=1 or `status`=2)
I have a feeling "status" might be reserved for something special. It might be worth a shot changing it to `status`.

Try wrapping brackets around the status column name:
SELECT *
FROM tblsignup
WHERE usr_email = 'amir#gmail.com'
AND ([status] = 1
OR [status] = 2);
EDIT
After reading your comment, why not use:
SELECT *
FROM tblsignup
WHERE usr_email = 'amir#gmail.com'
AND [status] > 0;

May it be that your column or table has case sensitive collation and the address is typed different ('Amir...')? As your query is correct SQL. You can find that with:
EXEC sp_help DatabaseName