如何在PostgreSQL查询中显示行号？

Question

我想显示PostgreSQL查询返回的每条记录的观察数.

我认为在8.4窗口函数中可以执行此功能.

Answer 1

select   row_number() over (order by <field> nulls last) as rownum, *
from     foo_tbl
order by <field>

如果没有必要订购,这个答案也可以简化:

select row_number() over(), *  -- notice: no fields are needed
from   foo_tbl

Answer 2

对于8.4之前的版本:

SELECT    count(*) rownum, foo.*
FROM      datatable foo
JOIN      datatable bar
          ON (foo.pk_id < bar.pk_id)
GROUP BY  foo.pk_id, foo.a, foo.b
ORDER BY  rownum
;

-- if there isn't a single unique/primary key field, you can concatenate fields
--    Example: ON (foo.a||foo.b||foo.c < bar.a||bar.b||bar.c)

希望这有助于某人.