I have an array of strings as one of my columns, and I want to sort the result by the first element of the array. This is what I have tried:
SELECT * FROM items ORDER BY aliases[0];
This did not work. How may this be accomplished?
Arrays in Postgres are indexed beginning at position 1, not 0. From the documentation:
By default PostgreSQL uses a one-based numbering convention for arrays, that is, an array of n elements starts with array[1] and ends with array[n].
With this in mind, try the following query:
SELECT * FROM items ORDER BY aliases[1];
Related
I want to extract a value out of an array of numerical values with index position in PostgreSQL.
My array is like {0.10,0.20,0.30}, type is numeric[], array position is an integer calculated with array_position. Syntax will be SELECT myarray[array_position];, but when I try (for example) :
SELECT'{0.10,0.20,0.30}'::numeric[][1];
It returned me the entire array.
How to extract a value out of an array with index position in PostgreSQL?
In your example [1] is the part of array definition: https://www.postgresql.org/docs/current/arrays.html#ARRAYS-DECLARATION
However, the current implementation ignores any supplied array size limits, i.e., the behavior is the same as for arrays of unspecified length.
Use parentheses to split the definition and reference:
SELECT ('{0.10,0.20,0.30}'::numeric[])[1];
I know there has to be a way to do this, but my googling was to no avail. I am trying to take a recordset, create an array and sort the elements alphabetically.
How would I accomplish this?
To do this you will need to use the ORDER BY clause in the ARRAY_AGG function.
Example:
SELECT ARRAY_AGG(fullname ORDER BY lastname)
FROM ...
This will return an array with names sorted by last name.
I want to select a single column in mgo which is array of strings currently using this returns a empty array
classifiedColl.Find(nil).Distinct("Tags", &tags)
and i want to group it how do i do it. The value i want to group is array of strings.
I have a problem with swift. I want to search an array of strings consists of 3 different elements filling this array in certain manner. Next i want to search the array for a subset of 3 particular strings next to each other and return their indexes. Is that a special array method for this?
Copied from comment:
Assumed i have an Int array like [1,2,1,3,2]. I want to search it for a subarray [1,2,1] and return indexes of those elements. Should i use findwithPredicate method?
I would just iterate the Array checking for matches.
Check the items in the array in sequence comparing the current item with the first item of the subarray. If it does not match move on. If it does start comparing the rest of the subarray, if it fails go bad to scanning the array.
I have two arrays
#one = ("1|1|the|dog|ran", "1|2|a|x|b", "2|8|e|s|e");
#two = ("1|2|a|x|b", "1|1|down|the|street", "2|8|e|s|e");
I need to match them by the first two "|" separated elements. So that when on $one[0] the search would return $two[1].
There are millions of lines in each array so I need the fastest way to do this.
EDIT:
Sorry for the confusion. I want to treat the first 2 "|" separated elements (ie. 1|2, 2|1) as a key for the array, loop through the first array and search the second array using that key to get the values in the second array. Does that help?
- For each record in the second array,
- Parse the record
- Add it to a hash keyed by the first two fields.
- For each record in the first array,
- Parse the record
- Look in the hash for a record with the appropriate key.
- If there is one,
- Do something with it.