Is there any way to execute the following Sql query in HiveQL?
select * from my_table
where (a,b,c) not in (x,y,z)
where a,b,c correspond respectively to x,y,z
Thanks:)
You'll have to break these down to separate conditions:
SELECT *
FROM my_table
WHERE a != x AND b != y AND c != z
Is this what you intend?
where a <> x or b <> y or c <> z
Or this?
where a not in (x, y, z) and
b not in (x, y, z) and
c not in (x, y, z)
Or some other variation?
Related
trying to learn answer set programming and decided to give the n-queens problem a go. This is what I have so far:-
% Queens are placed on an n x n chess board.
% Each queens must not attack each other.
% Represent the chess board squares.
square(1..n, 1..n).
% Place a Queen on one chess square.
queen(1..n).
5 { on(Q, X, Y) : queen(Q), square(X, Y) } 5.
:- queen(Q), on(Q, X, Y), on(Q, X', Y'), X != X', Y != Y'.
% Make sure each square only has one queen.
:- queen(Q), queen(Q'), on(Q, X, Y), on(Q', X, Y), Q != Q'.
% A Queen attacks another if both are on the same vertical, horizontal or diagonal.
:- on(Q, X, Y), on(Q', X, Y'), Q != Q', Y != Y'.
:- on(Q, X, Y), on(Q', X', Y), Q != Q', X != X'.
:- on(Q, X, Y), on(Q', X', Y'), Q != Q', |X-X'| = |Y-Y'|.
I am using clingo with the command - clingo n-queens.lp --const n=5 --models 2. The output that I get is:-
As you can see, despite stating that the queens should not be in the same column or row, the output contains some. What is wrong with the program?
Do you guys have some tips in general for getting better at ASP? I feel like I always get stuck when trying to describe the knowledge in ASP syntax.
There are 2 issues with your program:
5 { on(Q, X, Y) : queen(Q), square(X, Y) } 5.
should be
n { on(Q, X, Y) : queen(Q), square(X, Y) } n.
if you want it for anything else than n=5 and
:- queen(Q), on(Q, X, Y), on(Q, X', Y'), X != X', Y != Y'.
should be
:- queen(Q), on(Q, X, Y), on(Q, X', Y'), X != X'.
:- queen(Q), on(Q, X, Y), on(Q, X', Y'), Y != Y'.
This is because you want to write :- ..., X != X' OR Y != Y' and not :- ..., X != X' AND Y != Y' - causing this constraint to take effect only if both values differ.
For the output I added also:
#show on/3.
tested with the online version of clingo (added #const n=5. to the code):
clingo version 5.5.0
Reading from stdin
Solving...
Answer: 1
on(2,3,3) on(4,4,5) on(5,2,1) on(1,1,4) on(3,5,2)
SATISFIABLE
Please note that the online version provides a very neat example of n-queens.
Your program works but there is room for improvement. If you want to implement efficient code, a first hint would be to reduce the size of the ground logic program. This can be done - for example - by reducing the arity of predicates.
We got this query:
SELECT * FROM table WHERE A AND ( B = X1 OR B = X2 ) AND ( C = X3 OR D = TRUE ) AND E = 0;
I created this index:
CREATE INDEX _my_index ON public.table USING btree (A, B, C, D, E);
But I don't get any better performances ... how to deal with such queries for indexing ?
Thank you !
I'll assume that X1, X2 and X3 are constants and not table columns.
You won't be able to index C = X3 OR D = TRUE — OR is always a performance problem.
The condition B = X1 OR B = X2 should be rewritten to B IN (X1, X2).
Then this is the best index:
CREATE INDEX ON "table" (e, a, b);
If you always want to query for truth of a and e = 0, a partial index would be even better:
CREATE INDEX ON "table" (b) WHERE a AND e = 0;
If you need to index the conditions on c and d as well, and the table has a primary key, you can rewrite the query to:
SELECT * FROM "table"
WHERE a AND b IN (X1, X2) AND c = X3 AND e = 0
UNION
SELECT * FROM "table"
WHERE a AND b IN (X1, X2) AND d AND e = 0;
For this query, the following two indexes are commendable:
CREATE INDEX ON "table" (c, a, e, b);
CREATE INDEX ON "table" (e, a, d, b);
Again, you can move certain index columns into a WHERE condition if you always query for a certain value.
I would like to achieve the above for the following:
Rn = 0.009; % Resolution of simulation (in m^3)
Xs = -1 : Rn : 1;
Ys = -1 : Rn : 1;
Zs = 0 : Rn : 1;
[X Y Z] = meshgrid(Xs, Ys, Zs);
alpha = atan2(Z,X);
ze = x.^2 + y.^2; % define some condition
m = 0.59; % manual input
cond = (pi/3 <= alpha) & ...
(alpha <= (2*pi/3)) & ...
(m <= Z) & ...
(Z <= ze); % more conditions
xl = nnz(cond); % the number of non-zero elements
f = abs(xl*1000 - 90) % guessing m to get f as low as possible
How do I turn m into a variable for some f function so I can call fminsearch to quickly find the corresponding m for f ≈ 0?
In order to use m as a variable, you need to define a function handle. So you need to write:
cond = #(m) ((pi/3) <= alpha) & (alpha <= (2*pi/3)) & (m <= Z) & (Z <= ze);
However, you cannot use a function handle in the nnz routine, since it only accepts matrices as inputs. But, the solution to the problem is that you only have Boolean variables in cond. This means, you can simply sum over cond and get the same result as with nnz.
The only issue I see is how to implement the sum in fminsearch. Unfortunately, I do not have access to fminsearch, however I would assume that you can do something with reshape and then multiply with dot (i.e. .*) with the unity vector to get a sum. But you'll have to try that one out, not sure about it.
I am runining a following "simple query" from tables a1, a2, ..., a20. each table a1, a2, ...., a20 has milions of rows, and each of them have same columns, X, Y, Z.
CREATE TABLE A_bis as
SELECT
X, Y, Z
FROM a1
WHERE
Y= 3
UNION
SELECT
X, Y, Z
FROM a2
WHERE
Y= 3
UNION
SELECT
X, Y, Z
FROM a3
WHERE
Y= 3
UNION
...
SELECT
X, Y, Z
FROM a20
WHERE
Y= 3
and I get table A_bis, but it takes at least 20 minutes.
I'd like to:
a) optimize the query so it is faster.
b) improve the code (loop ? ) so I don't have to literally write a 7 lines for each of tables a1, .... a20 to get 130 lines of code
Comments answered your question A (Basically : Add an index on each aX table).
For the question B, you can use PostgreSQL inheritance:
CREATE TABLE aParent (x INT, y INT, z INT);
ALTER TABLE a1 INHERITS aParent;
ALTER TABLE a2 INHERITS aParent;
...
ALTER TABLE a20 INHERITS aParent;
Then you can do
SELECT X, Y, Z FROM aParent WHERE Y = 3;
Can someone tell me if I made this good? I am not so sure, especially about one thing explained by second diagram: does this green region means values of X AND Z, or rather X OR Z?
I made some corrects in code, but it seems that I am not using parentheses correctly. Don't know if this code is good
-- 1
/*
// Values stored in Y, that are parts of X and Z
"Y NOT IN (Y EXCEPT (UNION OF X AND Y))"
*/
SELECT Val FROM Y
EXCEPT
SELECT Val FROM X
EXCEPT
SELECT Val FROM Z
-- 2
/*
// Values stored in Y, that are parts of X and Z
"Y NOT IN (Y EXCEPT (UNION OF X AND Y))"
*/
SELECT VAL FROM Y
INTERSECT (
SELECT Val FROM Y
EXCEPT
SELECT Val FROM X
EXCEPT
SELECT Val FROM Z
)
-- 3
/*
// Values stored in X and Z. that are not a part of Y
"(UNION OF X & Z) EXCEPT Y"
*/
SELECT VAL FROM X
UNION
SELECT VAL FROM Z
EXCEPT
SELECT VAL FROM Y
-- 4
/*
// Every value of X, and same values from Y and Z
"(Y NOT IN (Y EXCEPT (UNION OF X AND Y))) UNION X"
*/
SELECT Val FROM X
UNION(
SELECT Val FROM Y
INTERSECT
SELECT Val FROM Z)
I agree with 1,3 and 4 but 2 should be:
SELECT VAL FROM Y
EXCEPT (
SELECT Val FROM Y
EXCEPT
SELECT Val FROM X
EXCEPT
SELECT Val FROM Z
or alternatively:
(SELECT Val FROM Y
INTERSECT
SELECT Val FROM X)
UNION
(SELECT Val FROM Y
INTERSECT
SELECT Val FROM X)