Good night, I am working in DB2 and I have been having some troubles making a query with case when
I have to find a way to make a query to define if a record of some category is valid only if the required fields of the relation are required and have been marked as selected, but in this case some registrys are empty and then I must exclude, I have a query like this:
Select (case (sum(category_id) where required='true' and selected='true') = sum(category_id) where required='true' then 'Yes'
else 'no'
from category_table
The problem, is that in some category the required field are all false (it's means do not exist) then I must put a condition like the sum equal to cero, but i always get a syntax error. I have something like this,
Select (case (sum(category_id) where required='true' and selected='true') = sum(category_id) where required='true' and (count(category_id) where required='true' != 0 ) then 'Yes'
else 'no'
from category_table
I have this problem in db2, saddly I can not put the original query hear because the proxy of my work don't le me pass emails to outside or even login at the web page from there.
I would be grateful for any help.
Have you tried using the VALUE function? if no rows will qualify the case conditions then you'll get Zero in the result.
Related
Can we use :xdo_user_name for filter logic with WebLogic?
I created a datamodel in oracle BI Publisher，with where clause like below:
WHERE (EMPLOYEE_NO = :xdo_user_name)
which works normally if I login with an employee account.
But I would like to make it show all data when I login as 'weblogic'，so I changed it to:
WHERE (EMPLOYEE_NO = :xdo_user_name
OR (CASE WHEN :xdo_user_name = 'weblogic' THEN 1=1 END))
Error is shown:
Character dat， right truncation occurred:for example， an update or insert value is a string that is too long for the column， or a datetime value cannot be assigned to a host variable， because it is too small.
Not so sure about why this error show up. Please advise.
Try it like this...
WHERE EMPLOYEE = CASE WHEN :xdo_user_name = 'weblogic' THEN EMPLOYEE ELSE :xdo_user_name END
this way, when logged in as 'weblogic', where condition will return True for every row - otherwise it will be True just for rows where EMPLOYEE = :xdo_user_name.
Regards...
I am new to Oracle apex.
I have a page with a form that is used to enter data into a table.
For Example there is P_ID, P_NAME, P_ADD_USER, P_VERIFIED_USER, P_SECOND_ID items. I want to make P_SECOND_ID read only based on multiple conditions.
Condition is
IF P_ADD_USER <> :APP_USER AND P_SECOND_ID = ' ' THEN
'P_SECOND_ID should be available to Edit.
ELSE
P_SECOND_ID will be read only.
I tried to use Type = Item!=Value but it is allowing me to add only one condition so is there any option that i can use both conditions and make that ITEM read only.
Condition I'd suggest in such a case is a function that returns a Boolean - if it returns TRUE, something will happen; otherwise, it won't.
So, if you want to make P_SECOND_ID editable if conditions you mentioned are satisfied, then you'd
return not ( :P_ADD_USER <> :APP_USER
and :P_SECOND_ID = ' '
);
Though, did you really want to say :P_SECOND_ID = ' '? Is there a space character in it? Should that, perhaps, be :P_SECOND_ID IS NULL?
SQL Expression allows you to include multiple conditions. You might want to rephrase your requirement to make the item read only ( versus making it editable ) under certain conditions. If I get your requirement right, the condition to make P_SECOND_ID read only is when
:P_ADD_USER = :APP_USER OR :P_SECOND_ID is not NULL
You can use this expression directly in the SQL Expression.
I have 2 values in table User: Address1, Address2. Both could be null. As part of a filter method, I am attempting something like the below:
var tempUsers = users.Where(q => q.Address1.ToLower().Contains(address.ToLower()) || q.Address2.ToLower().Contains(address.ToLower()));
This is returning a Null Reference Exception, and rightly so.
Linq queries need to be handled against null values
I would be attempting
null.ToLower() and null.Contains() within the query
What is the best way to go around it? If it was a simple 1 field Query, for e.g. just Address1, I would have simply filtered out all items with empty Address1, and continued normally in the second query. In this case, both fields are important to the filtering, as in, the input: address could be either in Address1 or Address2 of the User table.
I know this might not be possible in a 1 liner, but what is the best approach to take in terms of time and performance?
How about this:
var address = (GetAddressFromOuterWorld() ?? String.Empty).ToLower();
var tempUsers = users.Where(user => (user.Address1 ?? String.Empty).ToLower().Contains(address)
|| (user.Address2 ?? String.Empty).ToLower().Contains(address));
This definitely works with LINQ to Object, but probably fails with LINQ to SQL, but in that case you normally write user.Address1 == address || user.Addrss2 == address and your database uses a case-insensitive collate setting.
You can easily add null checks like this.
var tempUsers = users.Where(q =>
(!string.IsNullOrEmpty(q.Address1) && q.Address1.ToLower().Contains(address.ToLower())) ||
(!string.IsNullOrEmpty(q.Address2) && q.Address2.ToLower().Contains(address.ToLower())));
There is this stored procedure that builds a dynamic query string and then execute it. The sp works fine in development and testing environment, but the DBA of the client company has informed that this query is hitting really hard to the database in production. The IT area has asked us to tune up the query. So far so good, we've moved almost all this sp from building the query string dynamically into a single big query that performs really fast (compared to the old query).
We have found (among other things) that the sp built the where clause of the query string by evaluating if a parameter has a default value or a real value i.e.
IF P_WORKFLOWSTATUS <> 0 THEN
L_SQL := TRIM(L_SQL) || ' AND WORKFLOW.STATUS = ' || TO_CHAR(P_WORKFLOWSTATUS);
END IF;
So we optimized this behavior to
WHERE
...
AND (WORKFLOW.STATUS = P_WORKFLOWSTATUS OR P_WORKFLOWSTATUS = 0)
This kind of change has improved the query that affected numeric columns, but we have found a problem with a VARCHAR2 parameter and column. The current behavior is
--CLIENT.CODE is a VARCHAR2(14) column and there is an unique index for this column.
--The data stored in this field is like 'N0002077123', 'E0006015987' and similar
IF NVL(P_CLIENT_CODE, '') <> '' THEN
L_SQL := TRIM(L_SQL) || ' AND CLIENT.CODE = ''' || P_CLIENT_CODE || '''';
END IF;
We tried to change this to our optimized version of the query by doing
WHERE
...
AND (CLIENT.CODE = P_CLIENT_CODE OR NVL(P_CLIENT_CODE, '') = '')
but this change made the query lost performance. Is there a way to optimize this part of the query or should we turn our big query into a dynamic query (again) just to evaluate if this VARCHAR2 parameter should be added or not into the where clause?
Thanks in advance.
Oracle treats empty strings '' as NULL. So this condition NVL(P_CLIENT_CODE, '') = '' doesn't really make much sense. Moreover it will always be false, because here we are checking equality of NULLs, which is always false. To that end you might and probably should recode that part of the query as:
WHERE
...
AND ( (CLIENT.CODE = P_CLIENT_CODE) OR (CLIENT IS NULL) )
I recommend or to move this varchar2 parameters back to dynamic, or to use the following:
WHERE
...
AND CLIENT.CODE = nvl(P_CLIENT_CODE,CLIENT.CODE)
and be sure you have index on client.code.(Or the table partitioned on client.code, if possible.)
Of course, as it has already been said, you need need to perform correct null checks.
However, the trick is, the difference between
AND (CLIENT.CODE = P_CLIENT_CODE OR NVL(P_CLIENT_CODE, '') = '')
and
AND ( (CLIENT.CODE = P_CLIENT_CODE) OR (CLIENT IS NULL) )
is very unlikely to cause performance problems only by itself. I would even say that query with second clause could perform worse than with the first one, as it will yield true for more rows, resulting in larger result set for consequent joins/orders/filers etc.
I'd bet that adding this clause to your query somehow breaks its optimal execution plan. For instance, having obsolete statistics, the optimizer could make a sub-optimal decision to choose unselective index on client.code instead of others available.
However, it is hard to tell for sure without seeing actual (not the expected one, which you obtain with explain plan command!) execution plan of slow query and your table structure.
everyone! ))
Here is code.
var existingEntities = (from record in globalOne.serviceContext.records_out
where record.timestamp.Date == DateTime.Now.Date
select record ).ToList();
It doesn't work.
Another code:
var existingEntities = (from record in globalOne.serviceContext.records_out
where record.timestamp.Day == DateTime.Now.Day
select record ).ToList();
It does work.
So, problem id in next string:
where record.timestamp.**Date** == DateTime.Now.Date
also won't do
where record.timestamp.Date.Equals(DateTime.Now.Date)
But why? I have no clue. "Timestamp" field is dateTime field in MS SQL SERVER.
And - there is NO records in table.
And I almost forgot - what does it mean - "doesn't work".
App just will not reach the breakpoint after that query(first), without any error, without anything.
Thanks.
You can call record.timestamp.Date because EF can't convert it to required expression tree (then convert it to sql command). In fact EF supports limited number of functions and properties, But for DateTime, EF has some good Canonical functions. You can use them in your case, e.g you can use Day(),Month(),Year() functions to solve your problem (see the link).