DESCRIBE 문

DESCRIBE 문 (DESCRIBE Statements)

DESCRIBE 문은 테이블이나 뷰의 스키마, 카탈로그나 함수의 메타데이터, 또는 Flink 클러스터의 지정된 job을 설명하는 데 사용돼요.

출처: 문서

본문

DESCRIBE 문 실행 (Run a DESCRIBE statement)

DESCRIBE 문은 TableEnvironment의 executeSql() 메서드로 실행할 수 있어요. executeSql() 메서드는 성공적인 DESCRIBE 작업이면 객체를 반환하고, 그렇지 않으면 예외를 던져요. 다음 예시는 TableEnvironment에서 DESCRIBE 문을 실행하는 방법을 보여줘요. DESCRIBE 문은 SQL CLI에서도 실행할 수 있어요.

TableEnvironment tableEnv = TableEnvironment.create(...);

// register a table named "Orders"
tableEnv.executeSql(
        "CREATE TABLE Orders (" +
        " `user` BIGINT NOT NULl comment 'this is primary key'," +
        " product VARCHAR(32)," +
        " amount INT," +
        " ts TIMESTAMP(3) comment 'notice: watermark'," +
        " ptime AS PROCTIME() comment 'this is a computed column'," +
        " PRIMARY KEY(`user`) NOT ENFORCED," +
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
        ") with (...)");

// print the schema
tableEnv.executeSql("DESCRIBE Orders").print();

// print the schema
tableEnv.executeSql("DESC Orders").print();

// register a catalog named "cat2"
tableEnv.executeSql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')");

// print the metadata
tableEnv.executeSql("DESCRIBE CATALOG cat2").print();

// print the complete metadata
tableEnv.executeSql("DESC CATALOG EXTENDED cat2").print();

// register a function named "MySum"
tableEnv.executeSql("CREATE FUNCTION MySum as 'org.example.SumScalarFunction' USING JAR 'file://home/users/mysum-udf.jar';").print();

// print the metadata
tableEnv.executeSql("DESCRIBE FUNCTION MySum").print();

// print the complete metadata
tableEnv.executeSql("DESC FUNCTION EXTENDED MySum").print();

val tableEnv = TableEnvironment.create(...)

// register a table named "Orders"
 tableEnv.executeSql(
        "CREATE TABLE Orders (" +
        " `user` BIGINT NOT NULl comment 'this is primary key'," +
        " product VARCHAR(32)," +
        " amount INT," +
        " ts TIMESTAMP(3) comment 'notice: watermark'," +
        " ptime AS PROCTIME() comment 'this is a computed column'," +
        " PRIMARY KEY(`user`) NOT ENFORCED," +
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS" +
        ") with (...)")

// print the schema
tableEnv.executeSql("DESCRIBE Orders").print()

// print the schema
tableEnv.executeSql("DESC Orders").print()

// register a catalog named "cat2"
tableEnv.executeSql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')")

// print the metadata
tableEnv.executeSql("DESCRIBE CATALOG cat2").print()

// print the complete metadata
tableEnv.executeSql("DESC CATALOG EXTENDED cat2").print()


// register a function named "MySum"
tableEnv.executeSql("CREATE FUNCTION MySum as 'org.example.SumScalarFunction' USING JAR 'file://home/users/mysum-udf.jar';").print()

// print the metadata
tableEnv.executeSql("DESCRIBE FUNCTION MySum").print()

// print the complete metadata
tableEnv.executeSql("DESC FUNCTION EXTENDED MySum").print()

table_env = TableEnvironment.create(...)

# register a table named "Orders"
table_env.execute_sql( \
        "CREATE TABLE Orders (" 
        " `user` BIGINT NOT NULl comment 'this is primary key'," 
        " product VARCHAR(32),"
        " amount INT,"
        " ts TIMESTAMP(3) comment 'notice: watermark',"
        " ptime AS PROCTIME() comment 'this is a computed column',"
        " PRIMARY KEY(`user`) NOT ENFORCED,"
        " WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS"
        ") with (...)");

# print the schema
table_env.execute_sql("DESCRIBE Orders").print()

# print the schema
table_env.execute_sql("DESC Orders").print()

# register a catalog named "cat2"
table_env.execute_sql("CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db')")

# print the metadata
table_env.execute_sql("DESCRIBE CATALOG cat2").print()

# print the complete metadata
table_env.execute_sql("DESC CATALOG EXTENDED cat2").print()


// register a function named "MySum"
table_env.execute_sql("CREATE FUNCTION MySum as 'org.example.SumScalarFunction' USING JAR 'file://home/users/mysum-udf.jar';").print()

// print the metadata
table_env.execute_sql("DESCRIBE FUNCTION MySum").print()

// print the complete metadata
table_env.execute_sql("DESC FUNCTION EXTENDED MySum").print()

Flink SQL> CREATE TABLE Orders (
>  `user` BIGINT NOT NULl comment 'this is primary key',
>  product VARCHAR(32),
>  amount INT,
>  ts TIMESTAMP(3) comment 'notice: watermark',
>  ptime AS PROCTIME() comment 'this is a computed column',
>  PRIMARY KEY(`user`) NOT ENFORCED,
>  WATERMARK FOR ts AS ts - INTERVAL '1' SECONDS
> ) with (
>  ...
> );
[INFO] Table has been created.

Flink SQL> DESCRIBE Orders;

Flink SQL> DESC Orders;

Flink SQL> CREATE CATALOG cat2 WITH ('type'='generic_in_memory', 'default-database'='db');
[INFO] Execute statement succeeded.

Flink SQL> DESCRIBE CATALOG cat2;

Flink SQL> DESC CATALOG EXTENDED cat2;

Flink SQL> CREATE FUNCTION MySum as 'org.example.SumScalarFunction' USING JAR 'file://home/users/mysum-udf.jar';

Flink SQL> DESCRIBE FUNCTION MySum;

Flink SQL> DESC FUNCTION EXTENDED MySum;
      
Flink SQL> DESCRIBE JOB '228d70913eab60dda85c5e7f78b5782c';
      
Flink SQL> DESC JOB '228d70913eab60dda85c5e7f78b5782c';

위 예시의 결과는 Java, Scala, Python, SQL CLI에서 각각 확인할 수 있어요.

구문 (Syntax)

DESCRIBE TABLE

{ DESCRIBE | DESC } [catalog_name.][db_name.]table_name

DESCRIBE CATALOG

{ DESCRIBE | DESC } CATALOG [EXTENDED] catalog_name

DESCRIBE FUNCTION

{ DESCRIBE | DESC } FUNCTION [EXTENDED] [catalog_name.][db_name.]function_name

DESCRIBE JOB

주의: DESCRIBE JOB 문은 SQL CLI 또는 SQL Gateway에서만 동작해요.

DESCRIBE MODEL

{ DESCRIBE | DESC } MODEL [EXTENDED] [catalog_name.][db_name.]model_name

더 알아보기 (Learn more)