gaps-and-islands

I have a series of records containing some information (product type) with temporal validity. I would like to meld together adjacent validity intervals, provided that the grouping information (the product type) stays the same. I cannot use a simple GROUP BY with MIN and MAX , because some product types ( A , in the example) can "go away" and "come back". Using Oracle 11g. A similar question for MySQL is: How can I do a contiguous group by in MySQL? Input data : | PRODUCT | START_DATE | END_DATE | |---------|----------------------------------|----------------------------------| | A | July, 01

Thanks to Mike for the suggestion to add the create/insert statements. create table test ( pid integer not null, date date not null, primary key (pid, date) ); insert into test values (1,'2014-10-1') , (1,'2014-10-2') , (1,'2014-10-3') , (1,'2014-10-5') , (1,'2014-10-7') , (2,'2014-10-1') , (2,'2014-10-2') , (2,'2014-10-3') , (2,'2014-10-5') , (2,'2014-10-7'); I want to add a new column that is 'days in current streak' so the result would look like: pid | date | in_streak -------|-----------|---------- 1 | 2014-10-1 | 1 1 | 2014-10-2 | 2 1 | 2014-10-3 | 3 1 | 2014-10-5 | 1 1 | 2014-10-7 | 1 2

In PostgreSQL (9.3) I have a table defined as: CREATE TABLE charts ( recid serial NOT NULL, groupid text NOT NULL, chart_number integer NOT NULL, "timestamp" timestamp without time zone NOT NULL DEFAULT now(), modified timestamp without time zone NOT NULL DEFAULT now(), donotsee boolean, CONSTRAINT pk_charts PRIMARY KEY (recid), CONSTRAINT chart_groupid UNIQUE (groupid), CONSTRAINT charts_ichart_key UNIQUE (chart_number) ); CREATE TRIGGER update_modified BEFORE UPDATE ON charts FOR EACH ROW EXECUTE PROCEDURE update_modified(); I would like to replace the chart_number with a sequence like:

Guys i have a requirement to list all the dates of the previous month like below 20101201 20101202 20101203 20101204 20101205 .. .. .. .. .. .. .. .. 20101231 kindly let me know if any better way to do than this query. select TO_CHAR(TRUNC(SYSDATE,'MM')-1,'YYYYMMDD')-(level-1) as EACH_DATE from dual A connect by level < (TO_NUMBER(TO_CHAR(TRUNC(SYSDATE,'MM')-1,'DD'))+1) Also please let me know the problem with this query it says "missing right parenthesis" SELECT /*+ PARALLEL (A,8) */ /*+ DRIVING_STATE */ TO_CHAR(TRUNC(TRUNC(SYSDATE,'MM')-1,'MM'),'MONYYYY') "MONTH", TYPE AS "TRAFF", COLUMN, A

So lets say I have some records that look like: 2011-01-01 Cat 2011-01-02 Dog 2011-01-04 Horse 2011-01-06 Lion How can I construct a query that will return 2011-01-03 and 2011-01-05, ie the unused dates. I postdate blogs into the future and I want a query that will show me the days I don't have anything posted yet. It would look from the current date to 2 weeks into the future. Update: I am not too excited about building a permanent table of dates. After thinking about it though it seems like the solution might be to make a small stored procedure that creates a temp table. Something like:

I have a database table which holds each user's checkins in cities. I need to know how many days a user has been in a city, and then, how many visits a user has made to a city (a visit consists of consecutive days spent in a city). So, consider I have the following table (simplified, containing only the DATETIME s - same user and city): datetime ------------------- 2011-06-30 12:11:46 2011-07-01 13:16:34 2011-07-01 15:22:45 2011-07-01 22:35:00 2011-07-02 13:45:12 2011-08-01 00:11:45 2011-08-05 17:14:34 2011-08-05 18:11:46 2011-08-06 20:22:12 The number of days this user has been to this city