一开始还以为两个sql是一样的，结果。第二个sql会返回不可预料的结果。
SELECT
count(*) FILTER (WHERE ("periods" < 10 OR periods is NULL) ) ,
( SELECT to_date( now( ), 'yyyy-MM-dd hh24:mi:ss' ) ) AS cal_date
FROM
"dbname"."model"
WHERE
AND dr = 0
SELECT
count( periods < 10 OR periods is NULL) ,
( SELECT to_date( now( ), 'yyyy-MM-dd hh24:mi:ss' ) ) AS cal_date
FROM
"dbname"."model"
WHERE
AND dr = 0
