mySQL str_to_date()函数返回错误 [英] mySQL str_to_date() function returns error

问题描述

当尝试使用str_to_date()将我的Estimates表中的字符串日期值的列CreatedDate转换为mySQL日期格式时，我一直收到错误消息.我的数据列包含m/d/yy格式的日期(例如:1/26/16或3/3/16).

I keep receiving an error message when trying to convert a column, CreatedDate, of string date values in my Estimates table into the mySQL date format using str_to_date(). My column of data contains dates in m/d/yy format (for example: 1/26/16 or 3/3/16).

我运行了这个查询:

UPDATE Estimates
SET CreatedDate = str_to_date( CreatedDate, '%c/%e/%y' )

mySQL返回此错误消息:

mySQL is returning this error message:

Error
SQL query:
UPDATE Estimates
SET CreatedDate = str_to_date( CreatedDate, '%c/%e/%y' )
MySQL said: #1411 - Incorrect datetime value: '' for function str_to_date

我的查询出了什么问题?

What is wrong with my query?

推荐答案

清理数据的常用策略如下:

The usual strategy for cleaning up data like this is as follows:

ALTER TABLE Estimates CHANGE COLUMN CreatedDate CreatedDateString VARCHAR(255);
ALTER TABLE Estimates ADD COLUMN CreatedDate DATE

UPDATE Estimates SET CreatedDate=STR_TO_DATE(CreatedDateString, '%c/%e/%y'))
  WHERE CreatedDateString IS NOT NULL AND CreatedDateString != ''

然后，当您确信一切都已正确转换时:

Then when you're confident everything got converted correctly:

ALTER TABLE Estimates DROP COLUMN CreatedDateString

适当的DATE字段的优点是它们具有一致的格式，并且当您在它们上添加INDEX时，数据检索非常快，即使是在范围内，例如:

The advantage to proper DATE fields is they're in a consistent format and when you add an INDEX on them data retrieval is very fast, even on ranges, like:

SELECT * FROM Estimates WHERE CreatedDate BETWEEN '2016-01-01' AND '2016-06-30'

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