1. 常用的内置函数
2. .字符串转时间类型（TO_TIMESTAMP、TIMESTAMP和UNIX_TIMESTAMP）
2.1 使用
语法
TIMESTAMP TO_TIMESTAMP(BIGINT time)
TIMESTAMP TO_TIMESTAMP(VARCHAR date)
TIMESTAMP TO_TIMESTAMP(VARCHAR date, VARCHAR format)
使用
Flink SQL> select TO_TIMESTAMP('2022-09-05 18:51:44') ;
+----+-------------------------+
| op | EXPR$0 |
+----+-------------------------+
| +I | 2022-09-05 18:51:44.000 |
+----+-------------------------+
Received a total of 1 row
Flink SQL>
*****************************************************************
Flink SQL> select TIMESTAMP '2022-09-05 18:51:44' a;
+----+---------------------+
| op | a |
+----+---------------------+
| +I | 2022-09-05 18:51:44 |
+----+---------------------+
Received a total of 1 row
Flink SQL>
****************************************************************
Flink SQL> select UNIX_TIMESTAMP ('2022-09-05 18:51:44') a;
+----+----------------------+
| op | a |
+----+----------------------+
| +I | 1662375104 |
+----+----------------------+
Received a total of 1 row
Flink SQL>
2.1 时间类型转字符串（DATE_FORMAT和FROM_UNIXTIME）
Flink SQL> select DATE_FORMAT('2022-09-05 18:51:44', 'yyyy-MM-dd HH:mm:ss');
+----+--------------------------------+
| op | EXPR$0 |
+----+--------------------------------+
| +I | 2022-09-05 18:51:44 |
+----+--------------------------------+
Received a total of 1 row
Flink SQL>
*******************************************
将时间String 类型转化
TO_TIMESTAMP(string1[, string2]) # 将 字符串类型的时间戳 转化为 TIMESTAMP 类型，默认解析格式为 'yyyy-MM-dd HH:mm:ss'
TO_TIMESTAMP(DATE_FORMAT(LOCALTIMESTAMP, 'yyyy-MM-dd HH:mm:ss')) ts
TO_TIMESTAMP(string1[, string2]) # 将 字符串类型的时间戳 转化为 TIMESTAMP 类型，默认解析格式为 'yyyy-MM-dd HH:mm:ss'
select DATE_FORMAT(LOCALTIMESTAMP, 'yyyy-MM-dd HH:mm:ss');
Flink SQL> select DATE_FORMAT(LOCALTIMESTAMP, 'yyyy-MM-dd HH:mm:ss');
*************************************************************************************************************************
SQL Query Result (Table)
Table program finished. Page: Last of 1 Updated: 16:13:23.571
EXPR$0
2022-09-05 16:13:18