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
FROM customer
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=1144 width=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(dot)Elphick(at)lfix(dot)co(dot)uk
Isle of Wight http://www.lfix.co.uk/oliver
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