PSQL中的条件更新声明

我正在尝试在我的网站上执行条件更新。每当用户单击某个链接时，数据库中的全局计数器变量会自行增加。PSQL中的条件更新声明

并发症是，当计数器数量超过我记录的网站数量时，我希望计数器回到1.我有一个更新声明，但它不工作，我看不出为什么。

#Increment global counter, set it back to one when it exceeds the number of websites on record 
cursor.execute("UPDATE url_reroute_counter SET counter_num = "+ 
        " CASE"+ 
         " WHEN counter_num>(SELECT count(*) FROM url_reroute_targeturl)"+ 
          " THEN counter_num = 1"+ 
         " ELSE"+ 
          " counter_num = counter_num+1"+ 
        " END"+ 
        " WHERE name_of_counter = 'url_count'")`

运行这段代码让我以下异常：

django.db.utils.ProgrammingError: column "counter_num" is of type integer but expression is of type boolean 
    LINE 1: UPDATE url_reroute_counter SET counter_num = CASE WHEN coun... 
                 ^
    HINT: You will need to rewrite or cast the expression.

我不习惯在任何SQL语言，所以这里的任何HLEP表示赞赏使用条件语句。

来源

2016-06-10 GreenGodot

我觉得比较合适的标签是postgresql – e4c5

您的查询应该如下

cursor.execute("UPDATE url_reroute_counter SET counter_num = "+ 
       " CASE"+ 
        " WHEN counter_num>(SELECT count(*) FROM url_reroute_targeturl)"+ 
         " THEN 1"+ 
        " ELSE"+ 
         " counter_num+1"+ 
       " END"+ 
       " WHERE name_of_counter = 'url_count'")`

而且顺便说一句，在多线Python字符串，你并不需要所有的+号。这个：https://stackoverflow.com/a/10660443/267540

来源

2016-06-10 12:25:40 e4c5

现在我觉得很傻，这很明显。 – GreenGodot

碰巧每个人\ – e4c5

PSQL中的条件更新声明

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