Thread: Possible to UPDATE array[] columns?
Using SQL is it possible to UPDATE (append) onto an array[] column. For example say I have a column named "scores int[]". ID | scores 2 | {54,14,21,8} 3 | {12,0,7} Now I want to append the score of 12 on row:ID 2 so the new scores would read {54,14,21,8,12}. I thought maybe simply leaving the array key empty would auto-append "UPDATE table set scores[] = 12 WHERE id = 2", not so.... Thanks!
2009/10/30 Blake Starkenburg <blake@oldride.com>: > Using SQL is it possible to UPDATE (append) onto an array[] column. For > example say I have a column named "scores int[]". > > ID | scores > 2 | {54,14,21,8} > 3 | {12,0,7} > > Now I want to append the score of 12 on row:ID 2 so the new scores would > read {54,14,21,8,12}. I thought maybe simply leaving the array key empty > would auto-append "UPDATE table set scores[] = 12 WHERE id = 2", not so.... > You could use the concatenation operator so it would be: UPDATE TABLE set scores[] = scores[] || 12 WHERE id = 2; Thom
2009/10/30 Blake Starkenburg <blake@oldride.com>: > Using SQL is it possible to UPDATE (append) onto an array[] column. For > example say I have a column named "scores int[]". > > ID | scores > 2 | {54,14,21,8} > 3 | {12,0,7} > > Now I want to append the score of 12 on row:ID 2 so the new scores would > read {54,14,21,8,12}. I thought maybe simply leaving the array key empty > would auto-append "UPDATE table set scores[] = 12 WHERE id = 2", not so.... > > Thanks! > postgres=# create table foo(a int[]); CREATE TABLE postgres=# insert into foo values('{}'); INSERT 0 1 postgres=# update foo set a = a || 10; UPDATE 1 postgres=# update foo set a = a || 20; UPDATE 1 postgres=# update foo set a = a || 30; UPDATE 1 postgres=# select * from foo; a ------------ {10,20,30} (1 row) regards Pavel Stehule > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
On Fri, Oct 30, 2009 at 10:47:26AM -0700, Blake Starkenburg wrote: > ID | scores > 2 | {54,14,21,8} > 3 | {12,0,7} > > Now I want to append the score of 12 on row:ID 2 so the new scores would > read {54,14,21,8,12}. You need to use the normal array concatenation operator, ||, for example: UPDATE table SET scores = scores || ( SELECT scores FROM table WHERE id = 12) WHERE id = 2; This pulls out the scores for id=12 and appends them onto all the scores of the rows where id=2. The reason for the sub-select is that any query can only ever refer to the "current" row and not to any other row, the way to get around this is to join tables together and then you are able to compare every row with every other row. -- Sam http://samason.me.uk/
On Fri, Oct 30, 2009 at 06:23:28PM +0000, Sam Mason wrote: > On Fri, Oct 30, 2009 at 10:47:26AM -0700, Blake Starkenburg wrote: > > ID | scores > > 2 | {54,14,21,8} > > 3 | {12,0,7} > > > > Now I want to append the score of 12 on row:ID 2 so the new scores would > > read {54,14,21,8,12}. > > You need to use the normal array concatenation operator, ||, for > example: > > UPDATE table SET scores = scores || ( > SELECT scores FROM table WHERE id = 12) > WHERE id = 2; Doh, sorry, I was thinking you were asking for something more complicated. I don't seem to be doing very well here at all today! -- Sam http://samason.me.uk/
On Fri, Oct 30, 2009 at 1:47 PM, Blake Starkenburg <blake@oldride.com> wrote: > Using SQL is it possible to UPDATE (append) onto an array[] column. For > example say I have a column named "scores int[]". > > ID | scores > 2 | {54,14,21,8} > 3 | {12,0,7} > > Now I want to append the score of 12 on row:ID 2 so the new scores would > read {54,14,21,8,12}. I thought maybe simply leaving the array key empty > would auto-append "UPDATE table set scores[] = 12 WHERE id = 2", not so.... As other mentioned, you want the || operator. Just remember that all array operations read and write the entire array. This is one of the reasons why arrays are pretty lousy for OLTPish operations...they don't scale well and are inflexible in terms of querying. Before putting the array in the table, always ask yourself if you're better off with a separate table instead. The advantage of arrays of course are they they are very compact and you will get efficient use of the index on ID (if you are always interested in all the scores for an ID, maybe array is a good choice). merlin