如何选择字段的默认值 [英] How to SELECT DEFAULT value of a field

问题描述

我似乎找不到或编写一个选择默认值的sqlquery

I can't seem to find or write a sqlquery that SELECTS the DEFAULT VALUE

(而且我认为我无法在phpmyadmin中生成它以便复制)

(and I don't think I can generate it in phpmyadmin for me to copy)

我试图选择它，就好像它是一条记录，但无济于事...

I tried to SELECT it as if it was a record but to no avail...

 $defaultValue_find = mysql_query(
         "SELECT $group FROM grouptable WHERE $group='DEFAULT'")  
      or die("Query failed:".mysql_error());
 $defaultValue_fetch = mysql_fetch_row($defaultValue_find);
 $defaultValue = $defaultValue_fetch[0];
 echo $defaultValue;

推荐答案

"SELECT $group FROM grouptable WHERE $group=DEFAULT( $group ) "

或者我认为更好:

"SELECT DEFAULT( $group ) FROM grouptable LIMIT 1 "

---

更新-更正

正如@Jeff Caron指出的那样，以上内容仅在grouptable中至少有1行的情况下有效.如果即使分组表没有行也要得到结果，则可以使用以下方法:

As @Jeff Caron pointed, the above will only work if there is at least 1 row in grouptable. If you want the result even if the grouptable has no rows, you can use this:

"SELECT DEFAULT( $group ) 
 FROM (SELECT 1) AS dummy
   LEFT JOIN grouptable 
     ON True
 LIMIT 1 ;"

这篇关于如何选择字段的默认值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！