§ Oracle兼容-函数-SYSTIMESTAMP()函数
§ 1. 语法
SYSTIMESTAMP
SYSTIMESTAMP()
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§ 2. 定义和用法
SYSTIMESTAMP() 函数的作用是返回当前的日期和时间，类似于原生的函数NOW()。当未显式指定微秒位数时，时间的微秒位数默认值为6。
§ 3. 示例
-- 默认微秒位数为6
greatsql> SELECT SYSTIMESTAMP FROM DUAL;
greatsql> SELECT SYSTIMESTAMP, SYSTIMESTAMP() FROM DUAL;
+----------------------------+----------------------------+
| SYSTIMESTAMP | SYSTIMESTAMP() |
+----------------------------+----------------------------+
| 2023-11-02 17:43:25.990131 | 2023-11-02 17:43:25.990131 |
+----------------------------+----------------------------+
-- 自行指定微秒位数
greatsql> SELECT SYSTIMESTAMP(0), SYSTIMESTAMP(3) FROM DUAL;
+---------------------+-------------------------+
| SYSTIMESTAMP(0) | SYSTIMESTAMP(3) |
+---------------------+-------------------------+
| 2023-11-02 17:43:45 | 2023-11-02 17:43:45.189 |
+---------------------+-------------------------+
-- 指定微秒位数超出范围会报错
greatsql> SELECT SYSTIMESTAMP(10) FROM DUAL;
ERROR 1426 (42000): Too-big precision 10 specified for 'now'. Maximum is 6.
greatsql> SELECT SYSTIMESTAMP(-1) FROM DUAL;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-1) FROM DUAL' at line 1
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