i have a problem in my SQL statement where the situation is I need to choose the data which have to meet several criteria.
Question: How to determine existing old company - Lodgement of (F557 & F559) or (F558 & F559) or (F557 & F55)
my SQL :
SELECT * from roclodgingdetails
WHERE(vchformtrx='559' AND vchformtrx='557')
OR (vchformtrx='558' AND vchformtrx='559')
OR (vchformtrx='557' AND vchformtrx='55')
but this statement give me the result empty, even there is data meet the condition.
vchformtrx in a single row cannot have multiple values at once, for example;
WHERE (vchformtrx='559' AND vchformtrx='557')
...would require vchformtrx in a single row to have both the value 559 AND 557 at the same time to be true and return a result. The same goes for the other AND conditions. Using OR on 3 false conditions will still always result in false.
Your quoted question does not quite give me enough info on what the condition should really be, but - in short - you won't get any hints since your current condition can never be true.
Related
I know that through
select cases if char.substr(variable_name,1,3)="I22".
I can select values based on the first # of characters but this is not exactly my question. I need to select RANGE OF values that start with few characters, here is an example of what I want:
if I have the following cases:
I22A33
I22B33
I22C33
I22D33
So I want to select I22B33 and I22C33 out of the above 4 values, so it's like a range of cases between b and c.
One way to flag any cases that meet your criteria is using INDEX and a series of OR conditions. Not particularly modular, but if you just have a couple of conditions you're searching for it could get you on your way.
Edit: These searches are case-insensitive (due to UPCASE) and search for matches at the start of the string. To search for matches anywhere within the string set the condition to > 0 (instead of = 1).
COMPUTE f_I22 = (INDEX(UPCASE(var_name),'I22B33') = 1)
OR (INDEX(UPCASE(var_name),'I22C33') = 1) .
EXE .
Assuming in this range of values that you want to select, all the values will start with either "I22B" or "I22C", you can simply use:
select cases if char.substr(variable_name,1,4)="I22B" or
char.substr(variable_name,1,4)="I22C".
In my model Listing, among other columns I have these two:
- seller_currency
- bidder_currency
The value of listings.seller_currency and listings.bidder_currency can be either 1 (USD) or 0 (EUR).
I am trying to get all listings, where seller_currency and bidder_currency is 0 (EUR) or at least one of them is 0 (EUR).
Is there a better way to write the condition than this?
Listing.where('(seller_currency=0) OR (bidder_currency=0) OR (seller_currency=0 AND bidder_currency=0)')
According to your example, it is enough to fulfill at least one condition.
Listing.where(seller_currency: 0).or(Listing.where(bidder_currency: 0))
You only need one or condition and it covers the case where they are both 0. This way is preferable because it is a quicker query since it evaluates both columns at the same time.
Also, in case you wanted to use variables, the question mark stops sql injection.
Listing.where("(seller_currency=?) OR (bidder_currency=?)",0,0)
In the documentation for query expressions, I found:
Note that the order of the keys around the = sign in a join expression is significant.
I can't, however, find any information about how exactly the order is significant, what difference it makes, or what the rationale was for making an equality operator non-symmetric.
Can anyone either explain or point me to some better documentation?
This is important for joins. For example, if you look at the sample for leftOuterJoin:
query {
for student in db.Student do
leftOuterJoin selection in db.CourseSelection on
(student.StudentID = selection.StudentID) into result
for selection in result.DefaultIfEmpty() do
select (student, selection)
}
The order determines what happens when "missing" values occur. The key is this line in the docs:
If any group is empty, a group with a single default value is used instead.
With the current order, every StudentID within db.Student will be represented, even if db.CourseSelection doesn't have a matching element. If you reverse the order, the opposite is true - every "course selection" will be represented, with missing students getting the default value. This would mean that, in the above, if you switched the order, any students without a course selection would have no representation in the results, where the current order always shows every student.
The expression on the left of the operator must be derived from the "outer" thing being joined and the expression on the right must be derived from the "inner" thing (as you mention in your comment on Reed's answer). This is because of the LINQ API - the actual method that is invoked to build the query looks like this:
static member Join<'TOuter, 'TInner, 'TKey, 'TResult> :
outer:IQueryable<'TOuter> *
inner:IEnumerable<'TInner> *
outerKeySelector:Expression<Func<'TOuter, 'TKey>> *
innerKeySelector:Expression<Func<'TInner, 'TKey>> *
resultSelector:Expression<Func<'TOuter, 'TInner, 'TResult>> -> IQueryable<'TResult>
So you can't join on arbitrary boolean expressions (which you can do in SQL - something like JOIN ON a.x + b.y - 7 > a.w * b.z is fine in SQL but not in LINQ), you can only join based on an equality condition between explicit projections of the outer and inner tables. In my opinion this is a very unfortunate design decision, but it's been carried forward from LINQ into F#.
I wanna update my table for all persons whoes activity lasted toooo long. The update should correct one time and for the subsequent rows I need to deal with new result. So thought about something like
UPDATE summary_table st
SET st.screen_on=newScreenOnValue
st.active_screen_on=st.active_screen_on-(st.screen_on-newScreenOnValue) --old-value minus thedifference
FROM (
SUB-SELECT with rowid, newScreenOnValue ... JOIN ... WHERE....
) nv
WHERE (st.rowid=nv.rowid)
I know that I can update the first and the second value directly, by rerunning the same query. But my problem is the costs of the subselect seems quite high and therefore wanna avoid a double-update resp. double-run of the same query.
The above SELECT is just a informal way of writting what I think I would like to get. I know that the st doesn't work, but I left it here for better understanding. When I try the above statement I always get back a SyntaxError at the position the FROM ends.
This can be achieved as follows:
UPDATE summary_table st
SET (st.screen_on, st.active_screen_on) =
((SELECT newScreenOnValue, st.active_screen_on-(st.screen_on-newScreenOnValue)
FROM ...
JOIN...
WHERE..))
[WHERE if any additional condition required];
The above query works perfectly fine on informix tried and tested until you make any errors in the FROM, JOIN, WHERE clauses.
Cheers !
Syntax error because a comma is missing between the first and second columns you're updating.
Never use ROWID's, they're volatile and also not used by default with IDS, unless you specify so.
Why are you using a subquery?
I have a table with 1 million+ records that contain names. I would like to be able to sort the list by the first letter in the name.
.. ABCDEFGHIJKLMNOPQRSTUVWXYZ
What is the most efficient way to setup the db table to allow for searching by the first character in the table.name field?
The best idea right now is to add an extra field which stores the first character of the name as an observer, index that field and then sort by that field. Problem is it's no longer necessarily alphabetical.
Any suggestions?
You said in a comment:
so lets ignore the first letter part. How can I all records that start with A? All A's no B...z ? Thanks – AnApprentice Feb 21 at 15:30
I issume you meant How can I RETURN all records...
This is the answer:
select * from t
where substr(name, 1, 1) = 'A'
I agree with the questions above as to why you would want to do this -- a regular index on the whole field is functionally equivalent. PostgreSQL (with some new ones in v. 9) has some rather powerful indexing capabilities for special cases which you might want to read about here http://www.postgresql.org/docs/9.1/interactive/sql-createindex.html