PGSQL查询最近N天的数据及SQL语句实现替换字段内容（sql查询连续三天活跃用户）这都可以

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目录1、用SQL查询最近N天的数据2、用SQL语句实现替换字段里的内容3、SQL将查询结果赋值4、SQL查询字段内容为 NULL值时候赋值总结

思路：先获取当前的时间，然后更具当前时间去减去对应的天数，就可以得到需要的天数了。然后用这些天数作为条件，然后即可查询出需要多少天的数据了。

— 获取当前时间
SELECT CURRENT_TIMESTAMP;
— 或
SELECT now();
select CURRENT_TIMESTAMP :: DATE AS “当前日期”;
SELECT CURRENT_DATE;
select CURRENT_TIMESTAMP :: TIME AS “当前时间”;
SELECT CURRENT_TIME;

最近N天

— 最近7天
SELECT DATE( T ) AS DAY
FROM
generate_series ( ( CURRENT_TIMESTAMP – INTERVAL ‘6 day’ ) :: DATE,CURRENT_TIMESTAMP :: DATE, ‘1 days’ ) AS T ;

当然6 day、1 day这些也是可修改的；

–统计最近30、7、昨天、今天的数据
SELECT
count(*) AS AllData,
count(*) filter ( WHERE create_time BETWEEN ( SELECT CURRENT_DATE – INTERVAL ’30 day’ ) AND CURRENT_DATE ) AS Last30DayData,
count(*) filter ( WHERE create_time BETWEEN ( SELECT CURRENT_DATE – INTERVAL ‘7 day’ ) AND CURRENT_DATE ) AS Last7DayData,
count(*) filter ( WHERE create_time BETWEEN ( SELECT CURRENT_DATE – INTERVAL ‘1 day’ ) AND CURRENT_DATE ) AS YesterdayData,
count(*) filter ( WHERE create_time >=CURRENT_DATE ) AS todayAddData
FROM
table_name;

实例如下：查询lic_plate字段不为空和为空的最近7天的数据

— 查询lic_plate字段不为空的最近7天的数据
select count(tn.lic_plate) AS number,tn.create_time AS percentage
from table_name tn
where tn.create_time in (SELECT DATE(T) AS DAY
FROM generate_series((CURRENT_TIMESTAMP – INTERVAL ‘6 day’) :: DATE, CURRENT_TIMESTAMP :: DATE,’1 days’) AS T) AND lic_plate is not null
group by tn.create_time order by tn.create_time;

— 查询lic_plate字段为空的最近7天的数据
select count(id) AS number,CSQV.create_time AS percentage
from (select * from table_name tn where lic_plate is null) AS CSQV where CSQV.create_time in (SELECT DATE(T) AS DAY
FROM generate_series((CURRENT_TIMESTAMP – INTERVAL ‘6 day’) :: DATE, CURRENT_TIMESTAMP :: DATE,’1 days’) AS T)
group by CSQV.create_time;

思路：使用替换函数替换即可

— 替换语句
update 表名 set 替换字段名=replace(替换字段名,’被替换内容’,’替换内容’);

实例如下：将 my_test 表的 test_content 字段内容进行替换

update my_test set test_content=replace(test_content,’1′,’18’);

替换函数：如果没有可以创建，创建函数如下：

— replace all occurrences in string of old_substr with new_substr
— auto-generated definition
create function replace(text, text, text) returns text
immutable
strict
cost 1
language internal
as
$$begin
— missing source code
end;$$;

comment on function replace(text, text, text) is ‘replace all occurrences in string of old_substr with new_substr’;

–查询表数据，给test_content字段并赋值
select test_id,test_code,’测试数据’ test_content from my_test;
–查询表数据给自定义 ABCD字段并赋值
select test_id,test_code,’测试数据’ ABCD from my_test;

select test_id,test_code,COALESCE(test_content,’测试数据’) ABCD from my_test;
— ||
select test_id,test_code,
CASE
WHEN test_content IS NOT NULL THEN test_content
ELSE ‘测试数据’
END ABCD from my_test;

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