Re: Conditional operators ALL, ANY in WHERE clause

"Vladimir V. Zolotych" wrote: >Please give me hints how can I use "conditional operators ALL, ANY" in >WHERE clause. 
[This query would have been better directed to the pgsql-sql list.]
 >Some examples will be appreciated.

ALL is used to test a value against all of a list of items.

Find the customer whose account has been created the longest:
 SELECT id, date_opened   FROM customer   WHERE date_opened IS NOT NULL AND date_opened <= ALL (SELECT date_opened
FROMcustomer     WHERE date_opened IS NOT NULL);
 
   id   | date_opened  -------+-------------  25832 | 1998-01-05 (1 row)


ANY is used to compare against any item of the list; "x = ANY y" is the
same as "x IN y":
  SELECT COUNT(*)   FROM customer   WHERE area = ANY (SELECT id     FROM country);  count  -------    216 (1 row)


But note that use of ALL may be very inefficient:

bray=# explain select id,date_opened from customer where date_opened is not 
null and date_opened <= all (select date_opened from customer where 
date_opened is not null);
NOTICE:  QUERY PLAN:

Seq Scan on customer  (cost=0.00..240125.47 rows=1144 width=16) SubPlan   ->  Seq Scan on customer  (cost=0.00..139.89
rows=1144width=4)
 

EXPLAIN
bray=# explain select id,date_opened from customer where date_opened is not 
null and date_opened <= (select min(date_opened) from customer);
NOTICE:  QUERY PLAN:

Seq Scan on customer  (cost=0.00..148.47 rows=381 width=16) InitPlan   ->  Aggregate  (cost=139.89..139.89 rows=1
width=4)        ->  Seq Scan on customer  (cost=0.00..131.31 rows=3431 width=4)
 

EXPLAIN
-- 
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
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