The following Postgres table contains some sample content where the binary data is stored as bit varying (https://www.postgresql.org/docs/10/datatype-bit.html):
ID | Binary data
----------------------
1 | 01110
2 | 0111
3 | 011
4 | 01
5 | 0
6 | 00011
7 | 0001
8 | 000
9 | 00
10 | 0
11 | 110
12 | 11
13 | 1
Q: Is there any query (either native SQL or as Postgres function) to return all rows where the binary data field is equal to all sub-strings of the target bit array. To make it more clear lets look at the example search value 01101:
01101 -> no result
0110 -> no result
011 -> 3
01 -> 4
0 -> 5, 10
The result returned should contain the rows: 3, 4, 5 and 10.
Edit:
The working query is (thanks to Laurenz Albe):
SELECT * FROM table WHERE '01101' LIKE (table.binary_data::text || '%')
Furthermore I found this discussion about Postgres bit with fixed size vs bit varying helpful:
PostgreSQL Bitwise operators with bit varying "cannot AND bit strings of different sizes"
How about
WHERE '01101' LIKE (col2::text || '%')
I think you are looking for bitwise and:
where col2 & B'01101' = col2
Related
I would like to create a script that takes the rows of a table which have a specific mathematical difference in their ASCII sum and to add the rows to a separate table, or even to flag a different field when they have that difference.
For instance, I am looking to find when the ASCII sum of word A and the ASCII sum of word B, both stored in rows of a table, have a difference of 63 or 31.
I could probably use a loop to select these rows, but SQL is not my greatest virtue.
ItemID | asciiSum |ProperDiff
-------|----------|----------
1 | 100 |
2 | 37 |
3 | 69 |
4 | 23 |
5 | 6 |
6 | 38 |
After running the code, the field ProperDiff will be updated to contain 'yes' for ItemID 1,2,3,5,6, since the AsciiSum for 1 and 2 (100-37) = 63 etc.
This will not be fast, but I think it does what you want:
update t
set ProperDiff = 'yes'
where exists (select 1
from t t2
where abs(t2.AsciiSum - t.AsciiSum) in (63, 31)
);
It should work okay on small tables.
I have data of the form
-----------------------------|
6031566779420 | 25 | 163698 |
6031566779420 | 50 | 98862 |
6031566779420 | 75 | 70326 |
6031566779420 | 95 | 51156 |
6031566779420 | 100 | 43788 |
6036994077620 | 25 | 41002 |
6036994077620 | 50 | 21666 |
6036994077620 | 75 | 14604 |
6036994077620 | 95 | 11184 |
6036994077620 | 100 | 10506 |
------------------------------
and would like to create a dynamic number of new columns by treating each series of (25, 50, 75, 95, 100) and corresponding values as a new series. What I'm looking for as target output is,
--------------------------
| 25 | 163698 | 41002 |
| 50 | 98862 | 21666 |
| 75 | 70326 | 14604 |
| 95 | 51156 | 11184 |
| 100 | 43788 | 10506 |
--------------------------
I'm not sure what the name of the sql / postgres operation I want is called nor how to achieve it. In this case the data has 2 new columns but I'm trying to formulate a solution that has has many new columns as are groups of data in the output of the original query.
[Edit]
Thanks for the references to array_agg, that looks like it would be helpful! I should've mentioned this earlier but I'm using Redshift which reports this version of Postgres:
PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.1007
and it does not seem to support this function yet.
ERROR: function array_agg(numeric) does not exist
HINT: No function matches the given name and argument types. You may need to add explicit type casts.
Query failed
PostgreSQL said: function array_agg(numeric) does not exist
Hint: No function matches the given name and argument types. You may need to add explicit type casts.
Is crosstab the type of transformation I should be looking at? Or something else? Thanks again.
I've used array_agg() here
select idx,array_agg(val)
from t
group by idx
This will produce result like below:
idx array_agg
--- --------------
25 {163698,41002}
50 {98862,21666}
75 {70326,14604}
95 {11184,51156}
100 {43788,10506}
As you can see the second column is an array of two values(column idx) that corresponding to column idx
The following select queries will give you result with two separate column
Method : 1
SELECT idx
,col [1] col1 --First value in the array
,col [2] col2 --Second vlaue in the array
FROM (
SELECT idx
,array_agg(val) col
FROM t
GROUP BY idx
) s
Method : 2
SELECT idx
,(array_agg(val)) [1] col1 --First value in the array
,(array_agg(val)) [2] col2 --Second vlaue in the array
FROM t
GROUP BY idx
Result:
idx col1 col2
--- ------ -----
25 163698 41002
50 98862 21666
75 70326 14604
95 11184 51156
100 43788 10506
You can use array_agg function. Asuming, your columns are named A,B,C:
SELECT B, array_agg(C)
FROM table_name
GROUP BY B
Will get you output in array form. This is as close as you can get to variable columns in a simple query. If you really need variable columns, consider defining a PL/pgSQL procedure to convert array into columns.
I'm trying to create a "filter" with SQL.
I have a table named ARTICLE like this :
CODE | NAME | QUANTITY |
_______________|_________________|_______________
0020717270084 | MANGO FRUIT 1L | 3 |
0884394000774 | ALOE VERA 50CL | 4 |
16 | CHEWING GUM | 10 |
IGLOO | IGLOO ICE | 5 |
I want to do a SELECT with a verification on CODE.
If CODE is a number AND has a length of 8 OR 10 OR 13 digits, i display CODE ELSE i have to display * before CODE (simple concat).
I can do CASE WHEN but this one is a little bit tricky for me.
Thanks for your help.
You would do this with a case statement. Databases do the checks differently. The following is an approach using SQL Server:
select (case when len(code) in (8, 10, 13) and code not like '%[^0-9]%'
then code
else '*' + code
end)
Im using ransack search with ruby on rails and trying to output random rows between 1-6, whose time adds up to a given value specified by the search.
For example search for rows whose time value adds up to 40. In this case id 12 and 14 will be returned. Any combination between 1-6 can be randomly outputted.
If a combination of 3 rows meet the criteria then 3 rows should be outputted. likewise 1,2,3,4,5,6. If no single row or combination can be found then the output should return nil
id | title | time
----+-------------------------+-----------
26 | example | 10
27 | example | 26
14 | example | 20
28 | example | 50
12 | example | 20
20 | example | 6
Note - Not sure if ransack search is the best to perform this type of query
Thanks in advance
I want to represent the list "hi", "hello", "goodbye", "good day", "howdy" (with that order), in a SQL table:
pk | i | val
------------
1 | 0 | hi
0 | 2 | hello
2 | 3 | goodbye
3 | 4 | good day
5 | 6 | howdy
'pk' is the primary key column. Disregard its values.
'i' is the "index" that defines that order of the values in the 'val' column. It is only used to establish the order and the values are otherwise unimportant.
The problem I'm having is with inserting values into the list while maintaining the order. For example, if I want to insert "hey" and I want it to appear between "hello" and "goodbye", then I have to shift the 'i' values of "goodbye" and "good day" (but preferably not "howdy") to make room for the new entry.
So, is there a standard SQL pattern to do the shift operation, but only shift the elements that are necessary? (Note that a simple "UPDATE table SET i=i+1 WHERE i>=3" doesn't work, because it violates the uniqueness constraint on 'i', and also it updates the "howdy" row unnecessarily.)
Or, is there a better way to represent the ordered list? I suppose you could make 'i' a floating point value and choose values between, but then you have to have a separate rebalancing operation when no such value exists.
Or, is there some standard algorithm for generating string values between arbitrary other strings, if I were to make 'i' a varchar?
Or should I just represent it as a linked list? I was avoiding that because I'd like to also be able to do a SELECT .. ORDER BY to get all the elements in order.
As i read your post, I kept thinking 'linked list'
and at the end, I still think that's the way to go.
If you are using Oracle, and the linked list is a separate table (or even the same table with a self referencing id - which i would avoid) then you can use a CONNECT BY query and the pseudo-column LEVEL to determine sort order.
You can easily achieve this by using a cascading trigger that updates any 'index' entry equal to the new one on the insert/update operation to the index value +1. This will cascade through all rows until the first gap stops the cascade - see the second example in this blog entry for a PostgreSQL implementation.
This approach should work independent of the RDBMS used, provided it offers support for triggers to fire before an update/insert. It basically does what you'd do if you implemented your desired behavior in code (increase all following index values until you encounter a gap), but in a simpler and more effective way.
Alternatively, if you can live with a restriction to SQL Server, check the hierarchyid type. While mainly geared at defining nested hierarchies, you can use it for flat ordering as well. It somewhat resembles your approach using floats, as it allows insertion between two positions by assigning fractional values, thus avoiding the need to update other entries.
If you don't use numbers, but Strings, you may have a table:
pk | i | val
------------
1 | a0 | hi
0 | a2 | hello
2 | a3 | goodbye
3 | b | good day
5 | b1 | howdy
You may insert a4 between a3 and b, a21 between a2 and a3, a1 between a0 and a2 and so on. You would need a clever function, to generate an i for new value v between p and n, and the index can become longer and longer, or you need a big rebalancing from time to time.
Another approach could be, to implement a (double-)linked-list in the table, where you don't save indexes, but links to previous and next, which would mean, that you normally have to update 1-2 elements:
pk | prev | val
------------
1 | 0 | hi
0 | 1 | hello
2 | 0 | goodbye
3 | 2 | good day
5 | 3 | howdy
hey between hello & goodbye:
hey get's pk 6,
pk | prev | val
------------
1 | 0 | hi
0 | 1 | hello
6 | 0 | hi <- ins
2 | 6 | goodbye <- upd
3 | 2 | good day
5 | 3 | howdy
the previous element would be hello with pk=0, and goodbye, which linked to hello by now has to link to hey in future.
But I don't know, if it is possible to find a 'order by' mechanism for many db-implementations.
Since I had a similar problem, here is a very simple solution:
Make your i column floats, but insert integer values for the initial data:
pk | i | val
------------
1 | 0.0 | hi
0 | 2.0 | hello
2 | 3.0 | goodbye
3 | 4.0 | good day
5 | 6.0 | howdy
Then, if you want to insert something in between, just compute a float value in the middle between the two surrounding values:
pk | i | val
------------
1 | 0.0 | hi
0 | 2.0 | hello
2 | 3.0 | goodbye
3 | 4.0 | good day
5 | 6.0 | howdy
6 | 2.5 | hey
This way the number of inserts between the same two values is limited to the resolution of float values but for almost all cases that should be more than sufficient.