Help Center/ Data Lake Insight/ Flink SQL Syntax Reference/ Flink Opensource SQL 1.10 Syntax Reference/ Functions/ Built-In Functions/ Type Conversion Function
Updated on 2022-09-15 GMT+08:00
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Type Conversion Function

Syntax

CAST(value AS type)

Syntax Description

This function is used to forcibly convert types.

Precautions

If the input is NULL, NULL is returned.

Example

The following example converts the amount value to an integer.

insert into temp select cast(amount as INT) from source_stream;
Table 1 Examples of type conversion functions

Example

Description

Example

cast(v1 as string)

Converts v1 to a string. The value of v1 can be of the numeric type or of the timestamp, date, or time type.

Table T1:

| content (INT)           |
| -------------           |
| 5                       |

Statement:

SELECT
  cast(content as varchar)
FROM
  T1;

Result:

"5"

cast (v1 as int)

Converts v1 to the int type. The value of v1 can be a number or a character.

Table T1:

| content  (STRING)           |
| -------------               |
| "5"                         |

Statement:

SELECT
  cast(content as int)
FROM
  T1;

Result:

5

cast(v1 as timestamp)

Converts v1 to the timestamp type. The value of v1 can be of the string, date, or time type.

Table T1:

| content  (STRING)          |
| -------------              |
| "2018-01-01 00:00:01"     |

Statement:

SELECT
  cast(content as timestamp)
FROM
  T1;

Result:

1514736001000

cast(v1 as date)

Converts v1 to the date type. The value of v1 can be of the string or timestamp type.

Table T1:

| content  (TIMESTAMP)     |
| -------------            |
| 1514736001000            |

Statement:

SELECT
  cast(content as date)
FROM
  T1;

Result:

"2018-01-01"

Flink jobs do not support the conversion of bigint to timestamp using CAST. You can convert it using to_timestamp.

Detailed Sample Code

/** source **/
CREATE
TABLE car_infos (cast_int_to_string int, cast_String_to_int string,
case_string_to_timestamp string, case_timestamp_to_date timestamp(3)) WITH (
  'connector.type' = 'dis',
  'connector.region' = 'xxxxx',
  'connector.channel' = 'dis-input',
  'format.type' = 'json'
);
/** sink **/
CREATE
TABLE cars_infos_out (cast_int_to_string string, cast_String_to_int
int, case_string_to_timestamp timestamp(3), case_timestamp_to_date date) WITH (
  'connector.type' = 'dis',
  'connector.region' = 'xxxxx',
  'connector.channel' = 'dis-output',
  'format.type' = 'json'
);
/** Statistics on static car information**/
INSERT
INTO
  cars_infos_out
SELECT
  cast(cast_int_to_string as string),
  cast(cast_String_to_int as int),
  cast(case_string_to_timestamp as timestamp),
  cast(case_timestamp_to_date as date)
FROM
  car_infos;
Parent topic: Built-In Functions