§ Oracle兼容-函数-CURRENT_TIMESTAMP()函数
§ 1. 语法
CURRENT_TIMESTAMP[([n])]
1
§ 2. 定义和用法
返回当前时间戳。
参数 n 说明：
- n的值要小于等于6。
- 在ORACLE mode中，
CURRENT_TIMESTAMP等价于CURRENT_TIMESTAMP(6)，小数位是6（n=6），而CURRENT_TIMESTAMP()小数位是0（n=0）。而在DEFAULT mode中，CURRENT_TIMESTAMP和CURRENT_TIMESTAMP()等价，小数位都是0（n=0）。 - 在ORACLE mode中，输出值格式为
dd-mm-yy hh:mm:ss[.dec] am|pm timezone，而在DEFAULT mode中，输出值格式为yyyy-mm-dd hh24:mm:ss[.dec]。 - 在ORACLE mode中，时间格式与原有的不一样，这会导致部分函数（如
UNIX_TIMESTAMP()）当其参数值为CURRENT_TIMESTAMP时会显示异常。
§ 3. 示例
greatsql> SET sql_mode = ORACLE;
greatsql> SELECT CURRENT_TIMESTAMP;
+------------------------------------+
| CURRENT_TIMESTAMP |
+------------------------------------+
| 30-10-23 03:53:18.127314 PM +08:00 |
+------------------------------------+
greatsql> SELECT CURRENT_TIMESTAMP();
+-----------------------------+
| CURRENT_TIMESTAMP() |
+-----------------------------+
| 30-10-23 03:53:30 PM +08:00 |
+-----------------------------+
greatsql> SELECT CURRENT_TIMESTAMP(6);
+------------------------------------+
| CURRENT_TIMESTAMP(6) |
+------------------------------------+
| 30-10-23 03:53:41.122988 PM +08:00 |
+------------------------------------+
-- 小数位>6时会报错
greatsql> SELECT CURRENT_TIMESTAMP(7);
ERROR 1426 (42000): Too-big precision 7 specified for 'now'. Maximum is 6.
greatsql> CREATE TABLE t1(
id INT,
c VARCHAR2(64)
);
greatsql> INSERT INTO t1 VALUES(1, CURRENT_TIMESTAMP),
(2, CURRENT_TIMESTAMP()),
(3, CURRENT_TIMESTAMP(3)),
(4, CURRENT_TIMESTAMP(6));
greatsql> SELECT * FROM t1;
+------+------------------------------------+
| id | c |
+------+------------------------------------+
| 1 | 30-10-23 03:55:12.024380 PM +08:00 |
| 2 | 30-10-23 03:55:17 PM +08:00 |
| 3 | 30-10-23 03:55:26.559 PM +08:00 |
| 4 | 30-10-23 03:55:29.372250 PM +08:00 |
+------+------------------------------------+
greatsql> SET sql_mode = DEFAULT;
greatsql> SELECT CURRENT_TIMESTAMP;
+---------------------+
| CURRENT_TIMESTAMP |
+---------------------+
| 2023-10-30 15:55:59 |
+---------------------+
greatsql> SELECT CURRENT_TIMESTAMP();
+---------------------+
| CURRENT_TIMESTAMP() |
+---------------------+
| 2023-10-30 15:56:08 |
+---------------------+
greatsql> SELECT CURRENT_TIMESTAMP(6);
+----------------------------+
| CURRENT_TIMESTAMP(6) |
+----------------------------+
| 2023-10-30 15:56:17.512329 |
+----------------------------+
greatsql> INSERT INTO t1 VALUES(5, CURRENT_TIMESTAMP),
(6, CURRENT_TIMESTAMP()),
(7, CURRENT_TIMESTAMP(3)),
(8, CURRENT_TIMESTAMP(6));
greatsql> SELECT * FROM t1;
+------+------------------------------------+
| id | c |
+------+------------------------------------+
| 1 | 30-10-23 03:55:12.024380 PM +08:00 |
| 2 | 30-10-23 03:55:17 PM +08:00 |
| 3 | 30-10-23 03:55:26.559 PM +08:00 |
| 4 | 30-10-23 03:55:29.372250 PM +08:00 |
| 5 | 2023-10-30 15:56:31 |
| 6 | 2023-10-30 15:56:34 |
| 7 | 2023-10-30 15:56:37.998 |
| 7 | 2023-10-30 15:56:39.494867 |
+------+------------------------------------+
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