Oracle 参数 NLS_TIMESTAMP_FORMAT 官方解释，作用，如何配置最优化建议
本站中文解释
NLS_TIMESTAMP_FORMAT参数定义Oracle默认的时间戳格式，使用指定的格式在系统上向客户端传送与时间戳有关的信息，例如查询SELECT文中，把查询结果转换成单独的时间戳值，召回与时间戳有关的信息时。
正确设置NLS_TIMESTAMP_FORMAT的方法，首先需要确定用户的定义及操作系统的当前地点，IDE工具，客户端应用程序等，确定表示时间和时间戳的本地要求；然后依据要求的格式，使用Oracle支持的格式，在SQL中指定要使用的时间戳格式；最后在Oracle中实际设置NLS_TIMESTAMP_FORMAT参数，可以使用ALTER SESSION语句或者ALTER SYSTEM语句，例如：alter system set nls_timestamp_format=’yyyy-mm-dd hh24:mi:ss’;
官方英文解释
NLS_TIMESTAMP_FORMAT defines the default timestamp format to use with the TO_CHAR and TO_TIMESTAMP functions.
| Property | Description |
|---|---|
|
Parameter type |
String |
|
Syntax |
|
|
Default value |
Derived from |
|
Modifiable |
|
|
Modifiable in a PDB |
Yes |
|
Range of values |
Any valid datetime format mask |
|
Basic |
No |
The value must be surrounded by quotation marks as follows:
NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH:MI:SS.FF'
You can specify the value of NLS_TIMESTAMP_FORMAT by setting it in the initialization parameter file. You can specify its value for a client as a client environment variable.
You can also alter the value of NLS_TIMESTAMP_FORMAT by changing its value in the initialization parameter and then restarting the instance. To alter the value during a session use the ALTER SESSION SET statement.
Note:
The value of this initialization parameter NLS_TIMESTAMP_FORMAT is used to initialize the session value of this parameter, which is the actual value referenced by the SQL query processing. This initial value is overridden by a client-side value if the client uses the Oracle JDBC driver or if the client is OCI-based and the NLS_LANG client setting (environment variable) is defined. The initialization parameter value is, therefore, usually ignored.
See Also:
Oracle Database
Globalization Support Guide for more information about this parameter
