Question

假设我有一个像这样的MySQL数据库：

physicians database
Name   |   Specialty
----------------
Bob        Nurse
Susan      Nurse
Joan       Driver

我想更新数据库，以便将任何小于2的专业移到Other Specialties

所以数据库应该像这样更新：

physicians database
Name   |   Specialty
----------------
Bob        Nurse
Susan      Nurse
Joan       Other Specialties

此查询的真实数据库要大得多。

我尝试了这个查询：

UPDATE physicians 
 (SELECT Specialty FROM physicians GROUP BY Specialty
   HAVING COUNT(Specialty) = 1) AS counter
SET Specialty = 'Other Specialties'
WHERE Specity = counter

但是我收到语法错误，不确定我做错了什么。

Answer 1

试试这个UPDATE：

UPDATE physicians 
SET Specialty = 'Other Specialties'
WHERE Specialty IN (SELECT Specialty 
                   FROM (SELECT Specialty 
                         FROM physicians
                         GROUP BY Specialty
                         HAVING COUNT(*) = 1) AS t)

此UPDATE使用子查询以使所有Specialty值都是唯一的。然后，它使用这些值来执行UPDATE。

注意：子查询包含在另一个子查询中，因为SELECT无法直接使用UPDATE语句来更新同一个表。

Demo here

Answer 2

如果您想使用查询结构，可以将其更改为

UPDATE physicians inner join   
(SELECT Specialty FROM physicians GROUP BY Specialty
HAVING COUNT(Specialty) = 1) AS counter on physicians.speciality = counter.specialty
SET Specialty = 'Other Specialties'

Answer 3

update physicians
set Specialty = 'Other Specialties'
where Specialty in (
        select Specialty
        from physicians
        group by Specialty
        having COUNT(Specialty) < 2
        )

更新：更新医生 SET Specialty ='其他特产' 特色IN（SELECT专业 FROM（选择专业来自医生 GROUP BY专业有计数（专业）＆lt; 2）AS空间性值）;

更新列数＆lt;的列2在MySQL中

3 个答案: