我试图了解如何更新具有不同值的多行,我只是没有得到它。解决方案无处不在,但对我来说,它看起来很难理解。

例如,对一个查询进行三次更新:

UPDATE table_users
SET cod_user = '622057'
    , date = '12082014'
WHERE user_rol = 'student'
    AND cod_office = '17389551'; 

UPDATE table_users
SET cod_user = '2913659'
    , date = '12082014'
WHERE user_rol = 'assistant'
    AND cod_office = '17389551'; 

UPDATE table_users
SET cod_user = '6160230'
    , date = '12082014'
WHERE user_rol = 'admin'
    AND cod_office = '17389551'; 

我读了一个例子,但我真的不明白如何进行查询。即:

UPDATE table_to_update
SET cod_user= IF(cod_office = '17389551','622057','2913659','6160230')
    ,date = IF(cod_office = '17389551','12082014')
WHERE ?? IN (??) ;

我不完全清楚如何做查询,如果有多个条件在哪里和在if条件..有什么想法?


当前回答

UPDATE table_name
SET cod_user = 
    CASE 
    WHEN user_rol = 'student' THEN '622057'
    WHEN user_rol = 'assistant' THEN '2913659'
    WHEN user_rol = 'admin' THEN '6160230'
    END, date = '12082014'

WHERE user_rol IN ('student','assistant','admin')
AND cod_office = '17389551';

其他回答

UPDATE Table1 SET col1= col2 FROM (SELECT col2, col3 FROM Table2) as newTbl WHERE col4= col3

这里col4和col1在表1中。col2和col3在表2中,我试图更新每个col1,其中col4 = col3为每行不同的值

UPDATE table_name
SET cod_user = 
    CASE 
    WHEN user_rol = 'student' THEN '622057'
    WHEN user_rol = 'assistant' THEN '2913659'
    WHEN user_rol = 'admin' THEN '6160230'
    END, date = '12082014'

WHERE user_rol IN ('student','assistant','admin')
AND cod_office = '17389551';

你可以使用CASE语句来处理多个if/then场景:

UPDATE table_to_update 
SET  cod_user= CASE WHEN user_rol = 'student' THEN '622057'
                   WHEN user_rol = 'assistant' THEN '2913659'
                   WHEN user_rol = 'admin' THEN '6160230'
               END
    ,date = '12082014'
WHERE user_rol IN ('student','assistant','admin')
  AND cod_office = '17389551';

我是这样做的:

<update id="updateSettings" parameterType="PushSettings">
    <foreach collection="settings" item="setting">
        UPDATE push_setting SET status = #{setting.status}
        WHERE type = #{setting.type} AND user_id = #{userId};
    </foreach>
</update>

其中PushSettings是

public class PushSettings {

    private List<PushSetting> settings;
    private String userId;
}

它运行正常

MySQL提供了一种更易读的方式来将多个更新组合到一个查询中。这似乎更符合你描述的场景,更容易阅读,并避免了那些难以理清的多重情况。

INSERT INTO table_users (cod_user, date, user_rol, cod_office)
VALUES
('622057', '12082014', 'student', '17389551'),
('2913659', '12082014', 'assistant','17389551'),
('6160230', '12082014', 'admin', '17389551')
ON DUPLICATE KEY UPDATE
 cod_user=VALUES(cod_user), date=VALUES(date)

这里假设user_rol, cod_office组合是一个主键。如果其中只有一个是主键,则将另一个字段添加到UPDATE列表。 如果它们都不是主键(这似乎不太可能),那么这种方法总是会创建新记录——这可能不是我们想要的。

但是,这种方法使准备好的语句更容易构建,也更简洁。