CREATE EXTERNAL TABLE - Amazon Redshift
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CREATE EXTERNAL TABLE

Creates a new external table in the specified schema. All external tables must be created in an external schema. Search path isn't supported for external schemas and external tables. For more information, see CREATE EXTERNAL SCHEMA.

To create external tables, you must be the owner of the external schema or a superuser. To transfer ownership of an external schema, use ALTER SCHEMA to change the owner. Access to external tables is controlled by access to the external schema. You can't GRANT or REVOKE permissions on an external table. Instead, grant or revoke USAGE on the external schema.

In addition to external tables created using the CREATE EXTERNAL TABLE command, Amazon Redshift can reference external tables defined in an Amazon Glue or Amazon Lake Formation catalog or an Apache Hive metastore. Use the CREATE EXTERNAL SCHEMA command to register an external database defined in the external catalog and make the external tables available for use in Amazon Redshift. If the external table exists in an Amazon Glue or Amazon Lake Formation catalog or Hive metastore, you don't need to create the table using CREATE EXTERNAL TABLE. To view external tables, query the SVV_EXTERNAL_TABLES system view.

By running the CREATE EXTERNAL TABLE AS command, you can create an external table based on the column definition from a query and write the results of that query into Amazon S3. The results are in Apache Parquet or delimited text format. If the external table has a partition key or keys, Amazon Redshift partitions new files according to those partition keys and registers new partitions into the external catalog automatically. For more information about CREATE EXTERNAL TABLE AS, see Usage notes.

You can query an external table using the same SELECT syntax you use with other Amazon Redshift tables. You can also use the INSERT syntax to write new files into the location of external table on Amazon S3. For more information, see INSERT (external table).

To create a view with an external table, include the WITH NO SCHEMA BINDING clause in the CREATE VIEW statement.

You can't run CREATE EXTERNAL TABLE inside a transaction (BEGIN … END). For more information about transactions, see Serializable isolation.

Syntax

CREATE EXTERNAL TABLE
external_schema.table_name  
(column_name data_type [, …] )
[ PARTITIONED BY (col_name data_type [, … ] )] 
[ { ROW FORMAT DELIMITED row_format |
  ROW FORMAT SERDE 'serde_name' 
  [ WITH SERDEPROPERTIES ( 'property_name' = 'property_value' [, ...] ) ] } ]
STORED AS file_format
LOCATION { 's3://bucket/folder/' | 's3://bucket/manifest_file' }
[ TABLE PROPERTIES ( 'property_name'='property_value' [, ...] ) ]

The following is the syntax for CREATE EXTERNAL TABLE AS.

CREATE EXTERNAL TABLE
external_schema.table_name  
[ PARTITIONED BY (col_name [, … ] ) ] 
[ ROW FORMAT DELIMITED row_format ]
STORED AS file_format
LOCATION { 's3://bucket/folder/' }
[ TABLE PROPERTIES ( 'property_name'='property_value' [, ...] ) ]
 AS
 { select_statement }
         

Parameters

external_schema.table_name

The name of the table to be created, qualified by an external schema name. External tables must be created in an external schema. For more information, see CREATE EXTERNAL SCHEMA.

The maximum length for the table name is 127 bytes; longer names are truncated to 127 bytes. You can use UTF-8 multibyte characters up to a maximum of four bytes. Amazon Redshift enforces a limit of 9,900 tables per cluster, including user-defined temporary tables and temporary tables created by Amazon Redshift during query processing or system maintenance. Optionally, you can qualify the table name with the database name. In the following example, the database name is spectrum_db, the external schema name is spectrum_schema, and the table name is test.

create external table spectrum_db.spectrum_schema.test (c1 int) stored as parquet location 's3://mybucket/myfolder/';

If the database or schema specified doesn't exist, the table isn't created, and the statement returns an error. You can't create tables or views in the system databases template0, template1, and padb_harvest.

The table name must be a unique name for the specified schema.

For more information about valid names, see Names and identifiers.

( column_name data_type )

The name and data type of each column being created.

The maximum length for the column name is 127 bytes; longer names are truncated to 127 bytes. You can use UTF-8 multibyte characters up to a maximum of four bytes. You can't specify column names "$path" or "$size". For more information about valid names, see Names and identifiers.

By default, Amazon Redshift creates external tables with the pseudocolumns $path and $size. You can disable creation of pseudocolumns for a session by setting the spectrum_enable_pseudo_columns configuration parameter to false. For more information, see Pseudocolumns .

If pseudocolumns are enabled, the maximum number of columns you can define in a single table is 1,598. If pseudocolumns aren't enabled, the maximum number of columns you can define in a single table is 1,600.

If you are creating a "wide table," make sure that your list of columns doesn't exceed row-width boundaries for intermediate results during loads and query processing. For more information, see Usage notes.

For a CREATE EXTERNAL TABLE AS command, a column list is not required, because columns are derived from the query.

data_type

The following Data types are supported:

  • SMALLINT (INT2)

  • INTEGER (INT, INT4)

  • BIGINT (INT8)

  • DECIMAL (NUMERIC)

  • REAL (FLOAT4)

  • DOUBLE PRECISION (FLOAT8)

  • BOOLEAN (BOOL)

  • CHAR (CHARACTER)

  • VARCHAR (CHARACTER VARYING)

  • DATE (DATE data type can be used only with text, Parquet, or ORC data files, or as a partition column)

  • TIMESTAMP

For DATE, you can use the formats as described following. For month values represented using digits, the following formats are supported:

  • mm-dd-yyyy For example, 05-01-2017. This is the default.

  • yyyy-mm-dd, where the year is represented by more than 2 digits. For example, 2017-05-01.

For month values represented using the three letter abbreviation, the following formats are supported:

  • mmm-dd-yyyy For example, may-01-2017. This is the default.

  • dd-mmm-yyyy, where the year is represented by more than 2 digits. For example, 01-may-2017.

  • yyyy-mmm-dd, where the year is represented by more than 2 digits. For example, 2017-may-01.

For year values that are consistently less than 100, the year is calculated in the following manner:

  • If year is less than 70, the year is calculated as the year plus 2000. For example, the date 05-01-17 in the mm-dd-yyyy format is converted into 05-01-2017.

  • If year is less than 100 and greater than 69, the year is calculated as the year plus 1900. For example the date 05-01-89 in the mm-dd-yyyy format is converted into 05-01-1989.

  • For year values represented by two digits, add leading zeroes to represent the year in 4 digits.

Timestamp values in text files must be in the format yyyy-mm-dd HH:mm:ss.SSSSSS, as the following timestamp value shows: 2017-05-01 11:30:59.000000.

The length of a VARCHAR column is defined in bytes, not characters. For example, a VARCHAR(12) column can contain 12 single-byte characters or 6 two-byte characters. When you query an external table, results are truncated to fit the defined column size without returning an error. For more information, see Storage and ranges.

For best performance, we recommend specifying the smallest column size that fits your data. To find the maximum size in bytes for values in a column, use the OCTET_LENGTH function. The following example returns the maximum size of values in the email column.

select max(octet_length(email)) from users; max --- 62
PARTITIONED BY (col_name data_type [, … ] )

A clause that defines a partitioned table with one or more partition columns. A separate data directory is used for each specified combination, which can improve query performance in some circumstances. Partitioned columns don't exist within the table data itself. If you use a value for col_name that is the same as a table column, you get an error.

After creating a partitioned table, alter the table using an ALTER TABLE … ADD PARTITION statement to register new partitions to the external catalog. When you add a partition, you define the location of the subfolder on Amazon S3 that contains the partition data.

For example, if the table spectrum.lineitem_part is defined with PARTITIONED BY (l_shipdate date), run the following ALTER TABLE command to add a partition.

ALTER TABLE spectrum.lineitem_part ADD PARTITION (l_shipdate='1992-01-29') LOCATION 's3://spectrum-public/lineitem_partition/l_shipdate=1992-01-29';

If you are using CREATE EXTERNAL TABLE AS, you don't need to run ALTER TABLE ... ADD PARTITION . Amazon Redshift automatically registers new partitions in the external catalog. Amazon Redshift also automatically writes corresponding data to partitions in Amazon S3 based on the partition key or keys defined in the table.

To view partitions, query the SVV_EXTERNAL_PARTITIONS system view.

Note

For a CREATE EXTERNAL TABLE AS command, you don't need to specify the data type of the partition column because this column is derived from the query.

ROW FORMAT DELIMITED rowformat

A clause that specifies the format of the underlying data. Possible values for rowformat are as follows:

  • LINES TERMINATED BY 'delimiter'

  • FIELDS TERMINATED BY 'delimiter'

Specify a single ASCII character for 'delimiter'. You can specify non-printing ASCII characters using octal, in the format '\ddd' where d is an octal digit (0–7) up to ‘\177’. The following example specifies the BEL (bell) character using octal.

ROW FORMAT DELIMITED FIELDS TERMINATED BY '\007'

If ROW FORMAT is omitted, the default format is DELIMITED FIELDS TERMINATED BY '\A' (start of heading) and LINES TERMINATED BY '\n' (newline).

ROW FORMAT SERDE 'serde_name'
[WITH SERDEPROPERTIES ( 'property_name' = 'property_value' [, ...] ) ]

A clause that specifies the SERDE format for the underlying data.

'serde_name'

The name of the SerDe. You can specify the following formats:

  • org.apache.hadoop.hive.serde2.RegexSerDe

  • com.amazonaws.glue.serde.GrokSerDe

  • org.apache.hadoop.hive.serde2.OpenCSVSerde

    This parameter supports the following SerDe property for OpenCSVSerde:

    'wholeFile' = 'true'

    Set the wholeFile property to true to properly parse new line characters (\n) within quoted strings for OpenCSV requests.

  • org.openx.data.jsonserde.JsonSerDe

    • The JSON SERDE also supports Ion files.

    • The JSON must be well-formed.

    • Timestamps in Ion and JSON must use ISO8601 format.

    • This parameter supports the following SerDe property for JsonSerDe:

      'strip.outer.array'='true'

      Processes Ion/JSON files containing one very large array enclosed in outer brackets ( [ … ] ) as if it contains multiple JSON records within the array.

  • com.amazon.ionhiveserde.IonHiveSerDe

    The Amazon ION format provides text and binary formats, in addition to data types. For an external table that references data in ION format, you map each column in the external table to the corresponding element in the ION format data. For more information, see Amazon Ion. You also need to specify the input and output formats.

WITH SERDEPROPERTIES ( 'property_name' = 'property_value' [, ...] ) ]

Optionally, specify property names and values, separated by commas.

If ROW FORMAT is omitted, the default format is DELIMITED FIELDS TERMINATED BY '\A' (start of heading) and LINES TERMINATED BY '\n' (newline).

STORED AS file_format

The file format for data files.

Valid formats are as follows:

  • PARQUET

  • RCFILE (for data using ColumnarSerDe only, not LazyBinaryColumnarSerDe)

  • SEQUENCEFILE

  • TEXTFILE

  • ORC

  • AVRO

  • INPUTFORMAT 'input_format_classname' OUTPUTFORMAT 'output_format_classname'

The CREATE EXTERNAL TABLE AS command only supports two file formats, TEXTFILE and PARQUET.

For INPUTFORMAT and OUTPUTFORMAT, specify a class name, as the following example shows.

'org.apache.hadoop.mapred.TextInputFormat'
LOCATION { 's3://bucket/folder/' | 's3://bucket/manifest_file'}

The path to the Amazon S3 bucket or folder that contains the data files or a manifest file that contains a list of Amazon S3 object paths. The buckets must be in the same Amazon Region as the Amazon Redshift cluster. For a list of supported Amazon Regions, see Amazon Redshift Spectrum considerations.

If the path specifies a bucket or folder, for example 's3://mybucket/custdata/', Redshift Spectrum scans the files in the specified bucket or folder and any subfolders. Redshift Spectrum ignores hidden files and files that begin with a period or underscore.

If the path specifies a manifest file, the 's3://bucket/manifest_file' argument must explicitly reference a single file—for example, 's3://mybucket/manifest.txt'. It can't reference a key prefix.

The manifest is a text file in JSON format that lists the URL of each file that is to be loaded from Amazon S3 and the size of the file, in bytes. The URL includes the bucket name and full object path for the file. The files that are specified in the manifest can be in different buckets, but all the buckets must be in the same Amazon Region as the Amazon Redshift cluster. If a file is listed twice, the file is loaded twice. The following example shows the JSON for a manifest that loads three files.

{ "entries": [ {"url":"s3://mybucket-alpha/custdata.1", "meta": { "content_length": 5956875 } }, {"url":"s3://mybucket-alpha/custdata.2", "meta": { "content_length": 5997091 } }, {"url":"s3://mybucket-beta/custdata.1", "meta": { "content_length": 5978675 } } ] }

You can make the inclusion of a particular file mandatory. To do this, include a mandatory option at the file level in the manifest. When you query an external table with a mandatory file that is missing, the SELECT statement fails. Ensure that all files included in the definition of the external table are present. If they aren't all present, an error appears showing the first mandatory file that isn't found. The following example shows the JSON for a manifest with the mandatory option set to true.

{ "entries": [ {"url":"s3://mybucket-alpha/custdata.1", "mandatory":true, "meta": { "content_length": 5956875 } }, {"url":"s3://mybucket-alpha/custdata.2", "mandatory":false, "meta": { "content_length": 5997091 } }, {"url":"s3://mybucket-beta/custdata.1", "meta": { "content_length": 5978675 } } ] }

To reference files created using UNLOAD, you can use the manifest created using UNLOAD with the MANIFEST parameter. The manifest file is compatible with a manifest file for COPY from Amazon S3, but uses different keys. Keys that aren't used are ignored.

TABLE PROPERTIES ( 'property_name'='property_value' [, ...] )

A clause that sets the table definition for table properties.

Note

Table properties are case-sensitive.

'compression_type'='value'

A property that sets the type of compression to use if the file name doesn't contain an extension. If you set this property and there is a file extension, the extension is ignored and the value set by the property is used. Valid values for compression type are as follows:

  • bzip2

  • gzip

  • none

  • snappy

'data_cleansing_enabled'='true / false’

This property sets whether data handling is on for the table. When 'data_cleansing_enabled' is set to true, data handling is on for the table. When 'data_cleansing_enabled' is set to false, data handling is off for the table. Following is a list of the table–level data handling properites controlled by this property:

  • invalid_char_handling

  • replacement_char

  • surplus_char_handling

  • numeric_overflow_handling

For examples, see Data handling examples.

'invalid_char_handling'='value'

Specifies the action to perform when query results contain invalid UTF-8 character values. You can specify the following actions:

DISABLED

Doesn't perform invalid character handling.

FAIL

Cancels queries that return data containing invalid UTF-8 values.

SET_TO_NULL

Replaces invalid UTF-8 values with null.

DROP_ROW

Replaces each value in the row with null.

REPLACE

Replaces the invalid character with the replacement character you specify using replacement_char.

'replacement_char'='character

Specifies the replacement character to use when you set invalid_char_handling to REPLACE.

'numeric_overflow_handling'='value’

Specifies the action to perform when ORC data contains an integer (for example, BIGINT or int64) that is larger than the column definition (for example, SMALLINT or int16). You can specify the following actions:

DISABLED

Invalid character handling is turned off.

FAIL

Cancel the query when the data includes invalid characters.

SET_TO_NULL

Set invalid characters to null.

DROP_ROW

Set each value in the row to null.

'surplus_char_handling'='value'

Specifies how to handle data being loaded that exceeds the length of the data type defined for columns containing VARCHAR, CHAR, or string data. By default, Redshift Spectrum sets the value to null for data that exceeds the width of the column.

You can specify the following actions to perform when the query returns data that exceeds the column width:

SET_TO_NULL

Replaces data that exceeds the column width with null.

DISABLED

Doesn't perform surplus character handling.

FAIL

Cancels queries that return data exceeding the column width.

DROP_ROW

Replaces each value in the row with null.

TRUNCATE

Removes the characters that exceed the maximum number of characters defined for the column.

'numRows'='row_count'

A property that sets the numRows value for the table definition. To explicitly update an external table's statistics, set the numRows property to indicate the size of the table. Amazon Redshift doesn't analyze external tables to generate the table statistics that the query optimizer uses to generate a query plan. If table statistics aren't set for an external table, Amazon Redshift generates a query execution plan based on an assumption that external tables are the larger tables and local tables are the smaller tables.

'skip.header.line.count'='line_count'

A property that sets number of rows to skip at the beginning of each source file.

'serialization.null.format'=' '

A property that specifies Spectrum should return a NULL value when there is an exact match with the text supplied in a field.

'orc.schema.resolution'='mapping_type'

A property that sets the column mapping type for tables that use ORC data format. This property is ignored for other data formats.

Valid values for column mapping type are as follows:

  • name

  • position

If the orc.schema.resolution property is omitted, columns are mapped by name by default. If orc.schema.resolution is set to any value other than 'name' or 'position', columns are mapped by position. For more information about column mapping, see Mapping external table columns to ORC columns

Note

The COPY command maps to ORC data files only by position. The orc.schema.resolution table property has no effect on COPY command behavior.

'write.parallel'='on / off’

A property that sets whether CREATE EXTERNAL TABLE AS should write data in parallel. By default, CREATE EXTERNAL TABLE AS writes data in parallel to multiple files, according to the number of slices in the cluster. The default option is on. When 'write.parallel' is set to off, CREATE EXTERNAL TABLE AS writes to one or more data files serially onto Amazon S3. This table property also applies to any subsequent INSERT statement into the same external table.

‘write.maxfilesize.mb’=‘size’

A property that sets the maximum size (in MB) of each file written to Amazon S3 by CREATE EXTERNAL TABLE AS. The size must be a valid integer between 5 and 6200. The default maximum file size is 6,200 MB. This table property also applies to any subsequent INSERT statement into the same external table.

‘write.kms.key.id’=‘value

You can specify an Amazon Key Management Service key to enable Server–Side Encryption (SSE) for Amazon S3 objects, where value is one of the following:

  • auto to use the default Amazon KMS key stored in the Amazon S3 bucket.

  • kms-key that you specify to encrypt data.

select_statement

A statement that inserts one or more rows into the external table by defining any query. All rows that the query produces are written to Amazon S3 in either text or Parquet format based on the table definition.