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DESCRIBE TABLE
DESCRIBE TABLE
Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Description

DESCRIBE TABLE statement returns the basic metadata information of a table. The metadata information includes column name, column type and column comment. Optionally a partition spec or column name may be specified to return the metadata pertaining to a partition or column respectively.

Syntax

{ DESC | DESCRIBE } [ TABLE ] [ format ] table_identifier [ partition_spec ] [ col_name ] [ AS JSON ]

Parameters

  • format

    Specifies the optional format of describe output. If EXTENDED or FORMATTED is specified then additional metadata information (such as parent database, owner, and access time) is returned. Also if EXTENDED or FORMATTED is specified, then the metadata can be returned in JSON format by specifying AS JSON at the end of the statement.

  • table_identifier

    Specifies a table name, which may be optionally qualified with a database name.

    Syntax: [ database_name. ] table_name

  • partition_spec

    An optional parameter that specifies a comma separated list of key and value pairs for partitions. When specified, additional partition metadata is returned.

    Syntax: PARTITION ( partition_col_name = partition_col_val [ , ... ] )

  • col_name

    An optional parameter that specifies the column name that needs to be described. The supplied column name may be optionally qualified. Parameters partition_spec and col_name are mutually exclusive and can not be specified together. Currently nested columns are not allowed to be specified.

    JSON format is not currently supported for individual columns.

    Syntax: [ database_name. ] [ table_name. ] column_name

  • AS JSON

    An optional parameter to return the table metadata in JSON format. Only supported when EXTENDED or FORMATTED format is specified (both produce equivalent JSON).

    Syntax: [ AS JSON ]

    Schema:

    Below is the full JSON schema. In actual output, null fields are omitted and the JSON is not pretty-printed (see Examples).

      {
    "table_name": "<table_name>",
    "catalog_name": "<catalog_name>",
    "schema_name": "<innermost_namespace_name>",
    "namespace": ["<namespace_names>"],
    "type": "<table_type>",
    "provider": "<provider>",
    "columns": [
      {
        "name": "<name>",
        "type": <type_json>,
        "comment": "<comment>",
        "nullable": <boolean>,
        "default": "<default_val>"
      }
    ],
    "partition_values": {
      "<col_name>": "<val>"
    },
    "partition_columns": ["col1", "col2"],
    "clustering_columns": ["col1", "col2"],
    "location": "<path>",
    "view_text": "<view_text>",
    "view_original_text": "<view_original_text>",
    "view_schema_mode": "<view_schema_mode>",
    "view_catalog_and_namespace": "<view_catalog_and_namespace>",
    "view_query_output_columns": ["col1", "col2"],
    // Spark SQL configurations captured at the time of permanent view creation
    "view_creation_spark_configuration": {
      "conf1": "<value1>",
      "conf2": "<value2>"
    },
    "comment": "<comment>",
    "table_properties": {
      "property1": "<property1>",
      "property2": "<property2>"
    },
    "storage_properties": {
      "property1": "<property1>",
      "property2": "<property2>"
    },
    "serde_library": "<serde_library>",
    "input_format": "<input_format>",
    "output_format": "<output_format>",
    "num_buckets": <num_buckets>,
    "bucket_columns": ["<col_name>"],
    "sort_columns": ["<col_name>"],
    "created_time": "<yyyy-MM-dd'T'HH:mm:ss'Z'>",
    "created_by": "<created_by>",
    "last_access": "<yyyy-MM-dd'T'HH:mm:ss'Z'>",
    "partition_provider": "<partition_provider>",
    "collation": "<default_collation>"
  }

    Below are the schema definitions for <type_json>:

Spark SQL Data Types JSON Representation
ByteType { "name" : "tinyint" }
ShortType { "name" : "smallint" }
IntegerType { "name" : "int" }
LongType { "name" : "bigint" }
FloatType { "name" : "float" }
DoubleType { "name" : "double" }
DecimalType { "name" : "decimal", "precision": p, "scale": s }
StringType { "name" : "string", "collation": "<collation>" }
VarCharType { "name" : "varchar", "length": n }
CharType { "name" : "char", "length": n }
BinaryType { "name" : "binary" }
BooleanType { "name" : "boolean" }
DateType { "name" : "date" }
VariantType { "name" : "variant" }
TimestampType { "name" : "timestamp_ltz" }
TimestampNTZType { "name" : "timestamp_ntz" }
YearMonthIntervalType { "name" : "interval", "start_unit": "<start_unit>", "end_unit": "<end_unit>" }
DayTimeIntervalType { "name" : "interval", "start_unit": "<start_unit>", "end_unit": "<end_unit>" }
ArrayType { "name" : "array", "element_type": <type_json>, "element_nullable": <boolean> }
MapType { "name" : "map", "key_type": <type_json>, "value_type": <type_json>, "value_nullable": <boolean> }
StructType { "name" : "struct", "fields": [ {"name" : "field1", "type" : <type_json>, “nullable”: <boolean>, "comment": “<comment>”, "default": “<default_val>”}, ... ] }

Examples

-- Creates a table `customer`. Assumes current database is `salesdb`.
CREATE TABLE customer(
        cust_id INT,
        state VARCHAR(20),
        name STRING COMMENT 'Short name'
    )
    USING parquet
    PARTITIONED BY (state);
    
INSERT INTO customer PARTITION (state = 'AR') VALUES (100, 'Mike');
    
-- Returns basic metadata information for unqualified table `customer`
DESCRIBE TABLE customer;
+-----------------------+---------+----------+
|               col_name|data_type|   comment|
+-----------------------+---------+----------+
|                cust_id|      int|      null|
|                   name|   string|Short name|
|                  state|   string|      null|
|# Partition Information|         |          |
|             # col_name|data_type|   comment|
|                  state|   string|      null|
+-----------------------+---------+----------+

-- Returns basic metadata information for qualified table `customer`
DESCRIBE TABLE salesdb.customer;
+-----------------------+---------+----------+
|               col_name|data_type|   comment|
+-----------------------+---------+----------+
|                cust_id|      int|      null|
|                   name|   string|Short name|
|                  state|   string|      null|
|# Partition Information|         |          |
|             # col_name|data_type|   comment|
|                  state|   string|      null|
+-----------------------+---------+----------+

-- Returns additional metadata such as parent database, owner, access time etc.
DESCRIBE TABLE EXTENDED customer;
+----------------------------+------------------------------+----------+
|                    col_name|                     data_type|   comment|
+----------------------------+------------------------------+----------+
|                     cust_id|                           int|      null|
|                        name|                        string|Short name|
|                       state|                        string|      null|
|     # Partition Information|                              |          |
|                  # col_name|                     data_type|   comment|
|                       state|                        string|      null|
|                            |                              |          |
|# Detailed Table Information|                              |          |
|                    Database|                       default|          |
|                       Table|                      customer|          |
|                       Owner|                 <TABLE OWNER>|          |
|                Created Time|  Tue Apr 07 22:56:34 JST 2020|          |
|                 Last Access|                       UNKNOWN|          |
|                  Created By|               <SPARK VERSION>|          |
|                        Type|                       MANAGED|          |
|                    Provider|                       parquet|          |
|                    Location|file:/tmp/salesdb.db/custom...|          |
|               Serde Library|org.apache.hadoop.hive.ql.i...|          |
|                 InputFormat|org.apache.hadoop.hive.ql.i...|          |
|                OutputFormat|org.apache.hadoop.hive.ql.i...|          |
|          Partition Provider|                       Catalog|          |
+----------------------------+------------------------------+----------+

-- Returns partition metadata such as partitioning column name, column type and comment.
DESCRIBE TABLE EXTENDED customer PARTITION (state = 'AR');
+------------------------------+------------------------------+----------+
|                      col_name|                     data_type|   comment|
+------------------------------+------------------------------+----------+
|                       cust_id|                           int|      null|
|                          name|                        string|Short name|
|                         state|                        string|      null|
|       # Partition Information|                              |          |
|                    # col_name|                     data_type|   comment|
|                         state|                        string|      null|
|                              |                              |          |
|# Detailed Partition Inform...|                              |          |
|                      Database|                       default|          |
|                         Table|                      customer|          |
|              Partition Values|                    [state=AR]|          |
|                      Location|file:/tmp/salesdb.db/custom...|          |
|                 Serde Library|org.apache.hadoop.hive.ql.i...|          |
|                   InputFormat|org.apache.hadoop.hive.ql.i...|          |
|                  OutputFormat|org.apache.hadoop.hive.ql.i...|          |
|            Storage Properties|[serialization.format=1, pa...|          |
|          Partition Parameters|{transient_lastDdlTime=1586...|          |
|                  Created Time|  Tue Apr 07 23:05:43 JST 2020|          |
|                   Last Access|                       UNKNOWN|          |
|          Partition Statistics|                     659 bytes|          |
|                              |                              |          |
|         # Storage Information|                              |          |
|                      Location|file:/tmp/salesdb.db/custom...|          |
|                 Serde Library|org.apache.hadoop.hive.ql.i...|          |
|                   InputFormat|org.apache.hadoop.hive.ql.i...|          |
|                  OutputFormat|org.apache.hadoop.hive.ql.i...|          |
+------------------------------+------------------------------+----------+

-- Returns the metadata for `name` column.
-- Optional `TABLE` clause is omitted and column is fully qualified.
DESCRIBE customer salesdb.customer.name;
+---------+----------+
|info_name|info_value|
+---------+----------+
| col_name|      name|
|data_type|    string|
|  comment|Short name|
+---------+----------+

-- Returns the table metadata in JSON format.
DESC FORMATTED customer AS JSON;
{"table_name":"customer","catalog_name":"spark_catalog","schema_name":"default","namespace":["default"],"columns":[{"name":"cust_id","type":{"name":"integer"},"nullable":true},{"name":"name","type":{"name":"string"},"comment":"Short name","nullable":true},{"name":"state","type":{"name":"varchar","length":20},"nullable":true}],"location": "file:/tmp/salesdb.db/custom...","created_time":"2020-04-07T14:05:43Z","last_access":"UNKNOWN","created_by":"None","type":"MANAGED","provider":"parquet","partition_provider":"Catalog","partition_columns":["state"]}

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