MYSQL:最简单的方法是只更新非空的字段？

Question

假设我有这张表:

ID | col1 | col2 | col3 | col4
1  |  val |      |  val |

有没有办法修改此查询:

UPDATE table set col1 = "bla", col2 = "bla", col3 = "bla", col4 = "bla where id = 1

所以我最终得到:

ID | col1 | col2 | col3 | col4
1  |  val |  bla |  val |  bla

换句话说,查询必须只更新非空字段.你是怎样做的？

Answer 1

最简单的答案是使用 COALESCE

UPDATE table 
set     col1 = COALESCE(col1,"bla"), 
        col2 = COALESCE(col2,"bla"), 
        col3 = COALESCE(col3,"bla"), 
        col4 = COALESCE(col4,"bla")
where   id = 1

• SQLFiddle演示

其他链接.

• MySQL COALESCE