Question

我有2个表， med 和 viz ，结构如下：

MED

CREATE TABLE med 
(id_med INT AUTO_INCREMENT PRIMARY KEY,
name_m VARCHAR(50),
surname_m VARCHAR(50),
spec VARCHAR(50),
UNIQUE (surname_m,name_m));

即

CREATE TABLE viz
(id_m INT NOT NULL,
id_p INT  NOT NULL,
id_c INT  NOT NULL,
dt DATETIME)

我需要一个选择查询，该查询将提供med的全名，其中id_p＆lt; 250的计数和dt的年份是2010。以下查询给出了一个错误的结果：

select count(id_p)<250 as no_p,
(select distinct concat(name_m,' ',surname_m) from med where id_med=id_m) as fullname
from viz where year(dt)=2010;

Answer 1

尝试以下查询：

SELECT concat(m.name_m,' ',m.surname_m) AS fullname, COUNT(v.id_p)
FROM med m JOIN viz v
ON m.id_med = v.id_m
WHERE year(dt)=2010
GROUP BY m.id_med
HAVING COUNT(v.id_p) < 250

选择具有2个条件的计数

1 个答案: