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 defaultTo connect run:mysql -u rootTo 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*
FROMactor
WHERElast_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 c4from 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 actorWHERE 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,a4FROM    xxxWHERE   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,dsFROM    xxxxxxxxWHERE   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xxxGROUP 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='${bizdate}')
SELECT  city,line_name,fake_cnt,all_cnt,CONCAT(CAST(ROUND(100 * fake_cnt / all_cnt,2) AS STRING),'%') AS ratio
FROM    (SELECT  CASE    modeWHEN 'xx' THEN 'xxxxx'WHEN 'xx' THEN 'xxxxx'ELSE 'xxxxxx'END AS line_name,city,SUM(CASE WHEN cnt >= 1 THEN 1 ELSE 0 END) AS fake_cnt,COUNT(*) AS all_cntFROM    (SELECT  rider_._id,SUM(CASE WHEN location_type = '21' THEN 1 ELSE 0 END) AS cnt,ds,rider_.city_name AS city,id_mode.tms_line_name AS modeFROM    xxxxxxxxxx AS rider_LEFT JOIN   (SELECT  _id AS id,tms_line_nameFROM    xxxxxxxx.xxxdiWHERE   ds = '${bizdate}'AND     tms_line_name IS NOT NULL) id_modeON      id_mode.id = rider_._idWHERE   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_cntGROUP BY city,line_name --GROUP BY ROLLUP(city,mode)) mod_cnt
;

其中bizdate可以在调度配置中设置