Question

您好我有10列的列表（columnA，ColumnB，ColumnC ...），ColumnA用于ID。

我想以这种方式在php中进行更新：如果ColumnB不为空，则更新ColumnC，如果ColumnC不为空，则更新ColumnD ...直到找到空列。

我知道如何更新空列，但我不能详细说明如何实现IF语句。

到现在为止我有这个：

mysql_query("UPDATE tabel_name SET ColumnB = 'example' WHERE ColumnA = '$ID' ");

谢谢

Answer 1

您必须使用case仅更新选择性列。

示例：

update table_name set col1 = ( case when col1 is null then ? else col1 end ) , col2 = ( case when col2 is null then ? else col2 end ) -- , col3 = ... ;

使用mysql prepare替换查询参数。

另请参阅Quassnoi's answer to a similar posting。

更新：

如果ColumnB不为空则更新ColumnC，如果ColumnC不为空，则更新ColumnD ...直到找到空列。

您需要以相反的顺序设置列值检查。

update table_name set -- more next ( 4 to n ) columns here if required col3 = ( case when ( col2 is not null and col3 is null ) then 7 else col3 end ) , col2 = ( case when ( col1 is not null and col2 is null ) then 8 else col2 end ) , col1 = ( case when ( col1 is null ) then 9 else col1 end ) ;

示例表：

mysql> create table col_values ( id INT, col1 INT, col2 INT, col3 INT ); Query OK, 0 rows affected (0.06 sec) mysql> insert into col_values values ( 1, 1, 1, NULL ), ( 2, 1, NULL, NULL ), ( 3, NULL, NULL, NULL ); Query OK, 3 rows affected (0.01 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> select * from col_values; +------+------+------+------+ | id | col1 | col2 | col3 | +------+------+------+------+ | 1 | 1 | 1 | NULL | | 2 | 1 | NULL | NULL | | 3 | NULL | NULL | NULL | +------+------+------+------+ 3 rows in set (0.00 sec) mysql> update col_values set -> col3 = ( case when ( col2 is not NULL and col3 is NULL ) then 7 else col3 end ) -> , col2 = ( case when ( col1 is not NULL and col2 is NULL ) then 8 else col2 end ) -> , col1 = ( case when ( col1 is NULL ) then 9 else col1 end ) -> ; Query OK, 3 rows affected (0.02 sec) Rows matched: 3 Changed: 3 Warnings: 0 mysql> select * from col_values; +------+------+------+------+ | id | col1 | col2 | col3 | +------+------+------+------+ | 1 | 1 | 1 | 7 | | 2 | 1 | 8 | NULL | | 3 | 9 | NULL | NULL | +------+------+------+------+ 3 rows in set (0.00 sec)

您还可以使用if函数替代case语句。

mysql> truncate table col_values; Query OK, 3 rows affected (0.01 sec) mysql> insert into col_values values ( 1, 1, 1, NULL ), ( 2, 1, NULL, NULL ), ( 3, NULL, NULL, NULL ); Query OK, 3 rows affected (0.02 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> select * from col_values; +------+------+------+------+ | id | col1 | col2 | col3 | +------+------+------+------+ | 1 | 1 | 1 | NULL | | 2 | 1 | NULL | NULL | | 3 | NULL | NULL | NULL | +------+------+------+------+ 3 rows in set (0.00 sec) mysql> update col_values set -> col3 = if( ( col2 is not NULL and col3 is NULL ), 7, col3 ) -> , col2 = if( ( col1 is not NULL and col2 is NULL ), 8, col2 ) -> , col1 = if( col1 is NULL, 9, col1 ) -> ; Query OK, 3 rows affected (0.01 sec) Rows matched: 3 Changed: 3 Warnings: 0 mysql> select * from col_values; +------+------+------+------+ | id | col1 | col2 | col3 | +------+------+------+------+ | 1 | 1 | 1 | 7 | | 2 | 1 | 8 | NULL | | 3 | 9 | NULL | NULL | +------+------+------+------+ 3 rows in set (0.00 sec)

Answer 2

您可以执行类似

的操作

UPDATE table SET columnC = IF(columnB is not null, "value", columnC) where id = 1

Answer 3

您可以尝试这样的事情：

    $result=mysql_query('SELECT fav1, fav2, fav3, fav4, fav5 FROM users where id=".."');

    $row = mysql_fetch_array($result);

      foreach ($row as $columnName=>$value)
      {
         if ($value==null)
            {
             //update users set $columnName=pageID 
             break;
            }
      }

更新MySql字段（如果字段不为空，请转到下一个）

3 个答案: