聚合函数
-- 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
-- 更新语句
UPDATE weather
SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
WHERE date > '1994-11-28';
事务
-- 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;
单引号与双引号
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
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