postgresql - Join mutiple tables with date -


i have 3 tables

**table a** +-----------------+ | name      | id  | +------------------ | a1        | 1   | | a2        | 2   | | a3        | 3  | +------------------   **table b**                   +---------------------------------------+-----+-------+ | timestamp                             | type|    id | +---------------------------------------+-----+-------+ | 2013-05-10 08:10:10.161302-04         | b1   |  1   | | 2013-05-10 09:20:10.171302-04         | b1   |  1   | | 2013-05-12 08:10:10.161302-04         | b2   |  3   |  | 2013-05-13 08:10:10.161302-04         | b2   |  3   | | 2013-05-14 08:10:10.161302-04         | b1   |  2   | +---------------------------------------+------+------+  **table c**                   +---------------------------------------+-----+-------+ | timestamp                             | type|  id   | +---------------------------------------+-----+-------+ | 2013-05-12 08:10:10.161302-04         | c1   |  1   | | 2013-05-12 09:20:10.171302-04         | c2   |  2   | | 2013-05-12 08:10:10.161302-04         | c1   |  2   | | 2013-05-12 08:10:10.161302-04         | c3   |  1   | | 2013-05-13 08:10:10.161302-04         | c1   |  2   | | 2013-05-13 08:10:10.161302-04         | c3   |  3   | | 2013-05-14 08:10:10.161302-04         | c1   |  1   | +---------------------------------------+------+------+-  **expected result of query** +---------------------------------------+-----------------------------+ | date                | b.count(b1 entries)   |  c.count(c1 entries)  | +---------------------+-----------------------+-----------------------+ | 2013-05-10          |        2              |    0                  | | 2013-05-12          |        0              |    2                  | | 2013-05-13          |        0              |    1                  | | 2013-05-14          |        1              |    1                  | +---------------------+-----------------------+-----------------------+
  • the id in table b , table c refer table a.id
  • the query looking : for each day count number of b1 entries in table b , number of c1 entries in table c ids {1,2}

any suggestions welcome.

try query 

select  case when b.dtpart null a.dtpart else b.dtpart end dtpart, case when a.cnt null 0 else a.cnt end acnt,  case when b.cnt null 0 else b.cnt end bcnt   (select  date_trunc('day', "timestamp" ) dtpart, count(*) cnt  tbl1  "id" in (1,2) group date_trunc('day', "timestamp" ))  full join  (select  date_trunc('day', "timestamp" ) dtpart, count(*) cnt  tbl2  "id" in (1,2) group date_trunc('day', "timestamp" )) b on a.dtpart=b.dtpart

sql fiddle:

|                     dtpart | acnt | bcnt | -------------------------------------------- | may, 14 2013 00:00:00+0000 |    1 |    1 | | may, 10 2013 00:00:00+0000 |    2 |    0 | | may, 13 2013 00:00:00+0000 |    0 |    1 | | may, 12 2013 00:00:00+0000 |    0 |    4 |

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