Php 使用一个二进制字段从表中获取单独的值

我有如下学生出勤表：

id | Present | date
1  | 1
1  | 0
1  | 1
1  | 1
1  | 0

现在我想通过单个查询得到他在现场的总天数。可能吗

下面是我用来计算学生出席/缺席人数的方法：

select count(*) from table where present =1 
select count(*) from table where present =0

---

但是我想我可以从一个查询而不是两个查询中同时获得这两个查询。

您可以使用以下查询：

select (select count(*) from table where present=1) as "present"
      , (select count(*) from table where present=0) as "absent";

---

试试这个，效果很好：

SELECT SUM( present =1 ) AS present, SUM( present =0 ) AS absent
FROM details
WHERE id =1

屏幕截图：

SELECT SUM( present =1 ) AS present, SUM( present =0 ) AS absent
FROM details
WHERE id =1

试试这个： 适用于所有分组的学生

select id,present,absent from
(
    select id,sum(case when present = 1 then 1 else 0 end) as present,
        sum(case when present = 0 then 1 else 0 end) as absent
    from table_name
    group by id
) as absen

如果只想显示一个学生，只需在末尾添加

where子句

，如下所示：

select id,present,absent from
(
    select id,sum(case when present = 1 then 1 else 0 end) as present,
        sum(case when present = 0 then 1 else 0 end) as absent
    from table_name
    group by id
) as absen
where id = '1'

希望这对你有帮助