使用CAST或STR_TO_DATE链接JSON_EXTRACT失败 [英] Chaining JSON_EXTRACT with CAST or STR_TO_DATE fails

问题描述

我正在尝试从MySQL中的JSONFIELD数据"中提取日期时间.

I'm trying to extract a datetime from a JSONFIELD "data" in MySQL.

但是，如果我执行简单的JSON_EXTRACT，则返回字段类型为JSON.

If I do a simple JSON_EXTRACT however, the return field type is a JSON.

mysql> select JSON_EXTRACT(data, "$.new_time") from analytics limit 10;
+----------------------------------+
| JSON_EXTRACT(data, "$.new_time") |
+----------------------------------+
| NULL                             |
| "2016-09-30T04:00:00+00:00"      |
| "2016-09-29T05:30:00+00:00"      |
| NULL                             |
| "2016-10-01T05:30:00+00:00"      |
| "2016-09-27T23:00:00+00:00"      |
| NULL                             |
| "2016-09-23T01:30:00+00:00"      |
| "2016-09-23T04:00:00+00:00"      |
| "2016-09-27T01:30:00+00:00"      |
+----------------------------------+

我想将其转换为MySQL DATETIME.但是，如果我链接JSON_EXTRACT和STR_TO_DATETIME，我会得到所有NULL值:

I want to convert this to a MySQL DATETIME. But if I chain JSON_EXTRACT and STR_TO_DATETIME, I get all NULL values:

mysql> select STR_TO_DATE(JSON_EXTRACT(data, "$.new_time") ,"%Y-%m-%d") from analytics_calendaranalytics limit 10;
+-----------------------------------------------------------+
| STR_TO_DATE(JSON_EXTRACT(data, "$.new_time") ,"%Y-%m-%d") |
+-----------------------------------------------------------+
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
| NULL                                                      |
+-----------------------------------------------------------+

同样，以DATETIME进行CAST也会失败:

Likewise, a CAST as DATETIME also fails:

mysql> select CAST(JSON_EXTRACT(data, "$.new_time") as DATETIME) from analytics_calendaranalytics limit 10;
+----------------------------------------------------+
| CAST(JSON_EXTRACT(data, "$.new_time") as DATETIME) |
+----------------------------------------------------+
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
| NULL                                               |
+----------------------------------------------------+

当我从字符串值开始时，这两个命令都起作用:

Both these commands work when I start with the string value:

mysql> select CAST("2016-09-30T04:00:00+00:00" as DATETIME);
+-----------------------------------------------+
| CAST("2016-09-30T04:00:00+00:00" as DATETIME) |
+-----------------------------------------------+
| 2016-09-30 04:00:00                           |
+-----------------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> select STR_TO_DATE("2016-09-30T04:00:00+00:00", "%Y-%m-%d");
+------------------------------------------------------+
| STR_TO_DATE("2016-09-30T04:00:00+00:00", "%Y-%m-%d") |
+------------------------------------------------------+
| 2016-09-30                                           |
+------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

将感谢您为解决此问题提供的任何帮助！

Would appreciate any help in resolving this!

推荐答案

您必须使用

会工作.我要说的是，因为您尚未提供示例数据.我尝试如下:

Would work. I am saying would because you haven't provided sample data. I tried as follows:

select @js := JSON_OBJECT('new_time',"2016-09-30T04:00:00+00:00"  );

select CAST(JSON_UNQUOTE(JSON_EXTRACT(@js,'$.new_time')) as DATETIME);

以下查询也可以

 select STR_TO_DATE(JSON_UNQUOTE(JSON_EXTRACT(@js,'$.new_time')) ,"%Y-%m-%d");

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