Question

我有一个更新语句，用于更新字段x，y和z，其中id = xx。

在表格中，我有一些不同的x_created_datetime字段（对于不同人员维护/输入的记录的不同部分）。我想编写一个单独的查询，如果为null，将更新此字段，但如果不为null则不管它。

所以我拥有的是：

UPDATE newspapers
SET scan_notes = "data",
    scan_entered_by = "some_name",
    scan_modified_date = "current_unix_timestamp"
WHERE id = X

我需要的是一种添加以下内容的方法，但仍然总是更新以上内容：

scan_created_date = "current_unix_timestamp"
where scan_created_date is null

我希望我能在没有第二次交易的情况下做到这一点。关于如何实现这一目标的任何想法？

Answer 1

这样做：

UPDATE newspapers
SET scan_notes = "data",    
  scan_entered_by = "some_name",    
  scan_modified_date = "current_unix_timestamp",
  scan_created_date = COALESCE(scan_created_date, "current_unix_timestamp")
WHERE id = X

COALESCE函数选择第一个非空值。在这种情况下，它会将日期戳scan_created_date更新为相同的值（如果存在），否则它将取代您"current_unix_timestamp"替换的任何内容。

Answer 2

我认为您正在寻找的是IF()

UPDATE newspapers
SET scan_notes = "data",
    scan_entered_by = "some_name",
    scan_modified_date = "current_unix_timestamp",
    scan_created_date = IF(scan_created_date IS NOT NULL, "current_unix_timestamp", NULL)
WHERE id = X

Answer 3

mySQL有一个IFNULL函数，所以你可以这样做：

UPDATE newspapers
SET scan_notes = "data",
    scan_entered_by = "some_name",
    scan_modified_date = "current_unix_timestamp"
    scan_created_date = IFNULL( scan_created_date, "current_unix_timestamp" )
WHERE id = X

Answer 4

你可以使用COALESCE（）返回第一个NON-NULL值：

scan_created_date = COALESCE(scan_created_date, "current_unix_timestamp")

Answer 5

您可以这样做：

UPDATE newspapers a, newspapers b
SET a.scan_notes = "data",    
  a.scan_entered_by = "some_name",    
  a.scan_modified_date = "current_unix_timestamp",
  b.scan_created_date = "current_unix_timestamp"
WHERE a.id = X AND b.id = X AND b.scan_created_date is not NULL

Answer 6

它与Oracle的NVL相当。您可以使用参数

在预准备语句中使用它，如下所示

UPDATE
    tbl_cccustomerinfo
SET
    customerAddress = COALESCE(?,customerAddress),
    customerName =  COALESCE(?,customerName),
    description =  COALESCE(?,description)
WHERE
    contactNumber=?

不为空时更新字段

6 个答案: