-- 聚合查询

SELECT city, max(temp_lo)

FROM weather

WHERE city LIKE 'S%'

GROUP BY city

HAVING max(temp_lo) < 40; -- HAVING 子句始终包含聚合函数, 否则没有意义

-- 更新语句

UPDATE weather

    SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2

    WHERE date > '1994-11-28';

-- 事务

BEGIN;

UPDATE accounts SET balance = balance - 100.00

    WHERE name = 'Alice';

SAVEPOINT my_savepoint;

UPDATE accounts SET balance = balance + 100.00

    WHERE name = 'Bob';

-- oops ... forget that and use Wally's account

ROLLBACK TO my_savepoint;

UPDATE accounts SET balance = balance + 100.00

    WHERE name = 'Wally';

COMMIT;

francs=> create table test_3(id int4,name text);

CREATE TABLE  

francs=> insert into test_3 (id,name) values (1,'kate''s horse');

INSERT 0  1  

francs=>  select  *  from test_3;

id | name

----+--------------

 1  | kate's horse