SQL小示例

SQL示例

一、前言

• 安装MySQL

• 启动MySQL

  MySQL is configured to only allow connections from localhost by default

  To connect run:
  mysql -u root

  To start mysql now and restart at login:
  brew services start mysql

• 下载客户端工具Sequel Ace并登录

二、示例SQL

• where过滤数据

使用where过滤数据

SELECT
    *
FROM
    actor
WHERE
    last_name = 'ALLEN' OR last_name = 'DAVIS'
ORDER BY 
    `actor_id`;

where可以和and或者or联合使用，来圈定条件；常见的比较符：

=、<>、!=、>、<、>=、<=、IN、NOT IN、BETWEEN、LIKE、IS NULL、IS NOT NULL

• case when示例

统计address表格中，postal_code在区间的分布

select 

sum(
case when `postal_code` < 1000 then 1 else 0 
end
) as c1,

sum(
case 
	when (`postal_code` < 5000 and `postal_code`>=1000) then 1 else 0 
end
) as c2,

sum(
case 
	when (`postal_code` < 10000 and `postal_code`>=5000) then 1 else 0 
end
) as c3,

sum(
case when (`postal_code`>=10000) then 1 else 0 
end
) as c4

from address;

• 派生表的子查询

通过派生表temp1，统计符合条件的数量

select 
count(*) as cnt 
from(
	SELECT *
	FROM actor
	WHERE last_name = 'ALLEN' OR last_name = 'DAVIS'
	ORDER BY `actor_id`
    ) temp1;

• 常见通用格式(统计数字)

  SELECT t1.a1 -- 所有要展示的字段，都写在这里，可能不止来源一个表
  ,t1.a2
  ,COUNT(DISTINCT t1.a1) AS cnt
  ,t2.a3
  ,t2.a4
  FROM t1 -- 来源于第一个表
  LEFT JOIN (
  SELECT a3
  ,a4
  FROM xxx
  WHERE ds = 'xxx'
  ) t2 -- 第二个表
  ON t1.id = t2.id -- JOIN的关联条件
  WHERE t1.a1 = 'xx' -- 过滤条件
  AND t1.ds = '20230711'
  AND t1.a1 IS NOT NULL
  GROUP BY t1.a1 -- 分组：注意，所有select中出现的字段（除聚合函数外），都需要出现在GROUP BY中
  ,t1.a2
  ,t2.a3
  ,t2.a4
  HAVING cnt > 0 -- 对分组统计之后的最终数据做一个过滤，这里可以直接使用聚合函数as之后的别名
  ORDER BY cnt DESC -- 排序
  LIMIT 30
  ;

1.执行顺序：->from (去加载t1 和 t2这2个表 ) -> join -> on -> where -> group by->select 后面的聚合函数count,sum -> having -> distinct -> order by -> limit

2.FROM 子句执行顺序为从后往前、从右到左

• 查询最近几天某城市的xx

  SELECT ds
  ,SUM(CASE WHEN cnt >= 1 THEN 1 ELSE 0 END) AS fake_cnt_android
  ,COUNT(*) AS all_cnt_android
  FROM (
  SELECT user_id AS id
  ,SUM(CASE WHEN (location_type = '21' OR location_type = '25') THEN 1 ELSE 0 END) AS cnt
  ,ds
  FROM xxxxxxxx
  WHERE ds IN ('20230623','20230624','20230625','20230626','20230627')
  AND city_name = 'xx市'
  AND location_type IS NOT NULL -- 过滤掉无效数据
  AND location_type != -1 -- 过滤掉xxx
  GROUP BY ds
  ,id
  ) id_cnt
  GROUP BY ds
  ;

• 一个数据开发的ODPS SQL示例

  CREATE TABLE IF NOT EXISTS temp_xxx
  (
  city STRING COMMENT '城市'
  ,line_name STRING COMMENT 'xxx'
  ,fake_cnt BIGINT COMMENT 'xx数量'
  ,all_cnt BIGINT COMMENT '总数量'
  ,ratio STRING COMMENT '百分比'
  )
  COMMENT 'xxx情况表'
  PARTITIONED BY
  (
  ds STRING COMMENT 'day 分区字段'
  )
  LIFECYCLE 30
  ;

  INSERT OVERWRITE TABLE temp_xxx PARTITION (ds='{bizdate}') SELECT city ,line_name ,fake_cnt ,all_cnt ,CONCAT(CAST(ROUND(100 * fake_cnt / all_cnt,2) AS STRING),'%') AS ratio FROM ( SELECT CASE mode WHEN 'xx' THEN 'xxxxx' WHEN 'xx' THEN 'xxxxx' ELSE 'xxxxxx' END AS line_name ,city ,SUM(CASE WHEN cnt >= 1 THEN 1 ELSE 0 END) AS fake_cnt ,COUNT(*) AS all_cnt FROM ( SELECT rider_._id ,SUM(CASE WHEN location_type = '21' THEN 1 ELSE 0 END) AS cnt ,ds ,rider_.city_name AS city ,id_mode.tms_line_name AS mode FROM xxxxxxxxxx AS rider_ LEFT JOIN ( SELECT _id AS id ,tms_line_name FROM xxxxxxxx.xxxdi WHERE ds = '{bizdate}'
  AND tms_line_name IS NOT NULL
  ) id_mode
  ON id_mode.id = rider_._id
  WHERE ds = '${bizdate}'
  AND id IS NOT NULL
  AND city_id IN ('91','66')
  AND location_type IS NOT NULL -- 过滤掉无效数据
  GROUP BY ds
  ,rider.id
  ,mode
  ,rider.city_name
  ) id_cnt
  GROUP BY city
  ,line_name --GROUP BY ROLLUP(city,mode)
  ) mod_cnt
  ;

其中bizdate可以在调度配置中设置

附

参考资料：https://help.aliyun.com/zh/maxcompute/