PGSQL查询最近N天的数据及SQL语句实现替换字段内容

1、用SQL查询最近N天的数据

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;

2、用SQL语句实现替换字段里的内容

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\’;

3、SQL将查询结果赋值

–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;

4、SQL查询字段内容为 NULL值时候赋值

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;