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

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';

其他回答

在php中,使用mysqli实例的multi_query方法。

$sql = "SELECT COUNT(*) AS _num FROM test;
        INSERT INTO test(id) VALUES (1); 
        SELECT COUNT(*) AS _num FROM test; ";

$mysqli->multi_query($sql);

比较更新30,000 raw中的事务、插入、case方法的结果。

事务:5.5194580554962 插入:0.20669293403625 例:16.474853992462 多:0.0412278175354

如您所见,多语句查询比最高答案更有效。

以防万一你得到这样的错误信息:

PHP Warning:  Error while sending SET_OPTION packet

您可能需要增加mysql配置文件中的max_allowed_packet。

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';
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';
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

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