CUBRID学习笔记 41 sql语法之groupby 等

cubrid的中sql查询语法groupby

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GROUP BY ... HAVING Clause

按dept_no分组

SELECT dept_no, avg(sales_amount)
FROM sales_tbl
GROUP BY dept_no;

分组前先执行条件比较

SELECT dept_no, avg(sales_amount)
FROM sales_tbl
WHERE sales_amount > 100
GROUP BY dept_no;

分组后,having操作

SELECT dept_no, avg(sales_amount)
FROM sales_tbl
WHERE sales_amount > 100
GROUP BY dept_no HAVING avg(sales_amount) > 200;

使用别名

SELECT dept_no AS a1, avg(sales_amount) AS a2
FROM sales_tbl
WHERE sales_amount > 200 GROUP
BY a1 HAVING a2 > 200
ORDER BY a2;

WITH ROLLUP 分组后统计(没有用过)

SELECT dept_no AS a1, name AS a2, avg(sales_amount) AS a3
FROM sales_tbl
WHERE sales_amount > 100
GROUP BY a1, a2 WITH ROLLUP;

GROUP BY 排序
SELECT *
FROM sales_tbl
ORDER BY dept_no DESC, name ASC;

null排在前面还是后面
SELECT * FROM tbl ORDER BY b NULLS FIRST;
SELECT * FROM tbl ORDER BY b NULLS LAST;

limit 分页

SELECT t1.*
FROM (SELECT * FROM sales_tbl AS t2 WHERE sales_amount > 100 LIMIT 5) AS t1
LIMIT 1,3;

等同
SELECT t1.*
FROM (SELECT * FROM sales_tbl AS t2 WHERE sales_amount > 100 LIMIT 5) AS t1
LIMIT 3 OFFSET 1;

join 查询

1 Inner Join
SELECT DISTINCT h.host_year, o.host_nation
FROM history h INNER JOIN olympic o ON h.host_year = o.host_year AND o.host_year > 1950;
等同
SELECT DISTINCT h.host_year, o.host_nation
FROM history h, olympic o
WHERE h.host_year = o.host_year AND o.host_year > 1950;

2 Outer Join

SELECT DISTINCT h.host_year, o.host_year, o.host_nation
FROM history h RIGHT OUTER JOIN olympic o ON h.host_year = o.host_year
WHERE o.host_year > 1950;

SELECT DISTINCT h.host_year, o.host_year, o.host_nation
FROM olympic o LEFT OUTER JOIN history h ON h.host_year = o.host_year
WHERE o.host_year > 1950;

SELECT DISTINCT h.host_year, o.host_year, o.host_nation
FROM history h, olympic o
WHERE o.host_year = h.host_year(+) AND o.host_year > 1950;

SELECT DISTINCT h.host_year, o.host_year, o.host_nation
FROM olympic o LEFT OUTER JOIN history h ON h.host_year = o.host_year AND o.host_year > 1950;

3 CROSS JOIN

SELECT DISTINCT h.host_year, o.host_nation
FROM history h CROSS JOIN olympic o;
等同
SELECT DISTINCT h.host_year, o.host_nation
FROM history h, olympic o;

子查询

单行子查询

SELECT h.host_year, (SELECT host_nation FROM olympic o WHERE o.host_year=h.host_year) AS host_nation,
h.event_code, h.score, h.unit
FROM history h;

多行子查询

SELECT name, capital, list(SELECT host_city FROM olympic WHERE host_nation = name) AS host_cities
FROM nation;
结果

name capital host_cities

'Somalia' 'Mogadishu' {}
'Sri Lanka' 'Sri Jayewardenepura Kotte' {}
'Sao Tome & Principe' 'Sao Tome' {}
...
'U.S.S.R.' 'Moscow' {'Moscow'}
'Uruguay' 'Montevideo' {}
'United States of America' 'Washington.D.C' {'Atlanta ', 'St. Louis', 'Los Angeles', 'Los Angeles'}
'Uzbekistan' 'Tashkent' {}
'Vanuatu' 'Port Vila' {}

values函数
类似自定义了两列

SELECT a.*
FROM athlete a, (VALUES ('Jang Mi-Ran', 'F'), ('Son Yeon-Jae', 'F')) AS t(name, gender)
WHERE a.name=t.name AND a.gender=t.gender;

结果
code name gender nation_code event

    21111  'Jang Mi-Ran'       'F'      'KOR'              'Weight-lifting'
    21112  'Son Yeon-Jae'      'F'      'KOR'              'Rhythmic gymnastics'

for updae 为了更新或者删除,锁定前面查询出的结果

只有引用的表和视图被锁定
不能在子查询中使用,但是可以引用子查询
不能在包含group by ,distinct 或者汇总函数的sql声明中使用
不能引用union

CREATE TABLE t1(i INT);
INSERT INTO t1 VALUES (1), (2), (3), (4), (5);

CREATE TABLE t2(i INT);
INSERT INTO t2 VALUES (1), (2), (3), (4), (5);
CREATE INDEX idx_t2_i ON t2(i);

CREATE VIEW v12 AS SELECT t1.i AS i1, t2.i AS i2 FROM t1 INNER JOIN t2 ON t1.i=t2.i;

SELECT * FROM t1 ORDER BY 1 FOR UPDATE;
SELECT * FROM t1 ORDER BY 1 FOR UPDATE OF t1;
SELECT * FROM t1 INNER JOIN t2 ON t1.i=t2.i ORDER BY 1 FOR UPDATE OF t1, t2;

SELECT * FROM t1 INNER JOIN (SELECT * FROM t2 WHERE t2.i > 0) r ON t1.i=r.i WHERE t1.i > 0 ORDER BY 1 FOR UPDATE;

SELECT * FROM v12 ORDER BY 1 FOR UPDATE;
SELECT * FROM t1, (SELECT * FROM v12, t2 WHERE t2.i > 0 AND t2.i=v12.i1) r WHERE t1.i > 0 AND t1.i=r.i ORDER BY 1 FOR UPDATE OF r;