UNIQUE ( column_name [, ... ] )

[USING INDEX TABLESPACE tablespace]

[WITH ( FILLFACTOR=value )]

| PRIMARY KEY ( column_name [, ... ] )

[USING INDEX TABLESPACE tablespace]

[WITH ( FILLFACTOR=value )]

| CHECK ( expression )

where partition_type is:

LIST

| RANGE

where partition_specification is:

partition_element [, ...]

and partition_element is:

DEFAULT PARTITION name

| [PARTITION name] VALUES (list_value [,...] )

| [PARTITION name]

START ([datatype] 'start_value') [INCLUSIVE | EXCLUSIVE]

[ END ([datatype] 'end_value') [INCLUSIVE | EXCLUSIVE] ]

[ EVERY ([datatype] [number | INTERVAL] 'interval_value') ]

| [PARTITION name]

END ([datatype] 'end_value') [INCLUSIVE | EXCLUSIVE]

[ EVERY ([datatype] [number | INTERVAL] 'interval_value') ]

[ WITH ( partition_storage_parameter=value [, ... ] ) ]

[ TABLESPACE tablespace ]

where subpartition_spec or template_spec is:

subpartition_element [, ...]

and subpartition_element is:

DEFAULT SUBPARTITION name

| [SUBPARTITION name] VALUES (list_value [,...] )

| [SUBPARTITION name]

START ([datatype] 'start_value') [INCLUSIVE | EXCLUSIVE]

[ END ([datatype] 'end_value') [INCLUSIVE | EXCLUSIVE] ]

[ EVERY ([datatype] [number | INTERVAL] 'interval_value') ]

| [SUBPARTITION name]

END ([datatype] 'end_value') [INCLUSIVE | EXCLUSIVE]

[ EVERY ([datatype] [number | INTERVAL] 'interval_value') ]

[ WITH ( partition_storage_parameter=value [, ... ] ) ]

[ TABLESPACE tablespace ]

table_name

The name (optionally schema-qualified) of the table to be created.

column_name

The name of a column to be created in the new table.

data_type

The data type of the column. This may include array specifiers.

DEFAULT default_expr

The DEFAULT clause assigns a default data value for the column whose column definition it appears within. The value is any variable-free expression (subqueries

and cross-references to other columns in the current table are not allowed). The data type of the default expression must match the data type of the column. The default expression will be used in any insert operation that does not specify a value for the column. If there is no default for a column, then the default is null.

INHERITS

The optional INHERITS clause specifies a list of tables from which the new table automatically inherits all columns. Use of INHERITS creates a persistent

relationship between the new child table and its parent table(s). Schema modifications to the parent(s) normally propagate to children as well, and by default

the data of the child table is included in scans of the parent(s).

In Greenplum Database, the INHERITS clause is not used when creating partitioned tables. Although the concept of inheritance is used in partition hierarchies, the

inheritance structure of a partitioned table is created using the PARTITION BY clause. If the same column name exists in more than one parent table, an error is reported unless the data types of the columns match in each of the parent tables. If there is no conflict, then the duplicate columns are merged to form a single column in the new table. If the column name list of the new table contains a column name that is also inherited, the data type must likewise match the inherited column(s), and the column definitions are merged into one. However, inherited and new column declarations of the same name need not specify identical constraints: all constraints provided from any declaration are merged together and all are applied to the new table. If the new table explicitly specifies a default value for the column, this default overrides any defaults from inherited declarations of the column. Otherwise, any parents that specify default values for the column must all specify the same default, or an error will be reported.

LIKE other_table [{INCLUDING | EXCLUDING} {DEFAULTS |

CONSTRAINTS}]

The LIKE clause specifies a table from which the new table automatically copies all column names, data types, not-null constraints, and distribution policy. Storage

properties like append-only or partition structure are not copied. Unlike INHERITS, the new table and original table are completely decoupled after creation is complete. Default expressions for the copied column definitions will only be copied if INCLUDING DEFAULTS is specified. The default behavior is to exclude default

expressions, resulting in the copied columns in the new table having null defaults. Not-null constraints are always copied to the new table. CHECK constraints will only be copied if INCLUDING CONSTRAINTS is specified; other types of constraints will never be copied. Also, no distinction is made between column constraints and table constraints — when constraints are requested, all check constraints are copied. Note also that unlike INHERITS, copied columns and constraints are not merged with similarly named columns and constraints. If the same name is specified explicitly or in another LIKE clause an error is signalled.

CONSTRAINT constraint_name

An optional name for a column or table constraint. If the constraint is violated, the constraint name is present in error messages, so constraint names like column must be positive can be used to communicate helpful constraint information to client applications. (Double-quotes are needed to specify constraint names that contain spaces.) If a constraint name is not specified, the system generates a name.

NULL | NOT NULL

Specifies if the column is or is not allowed to contain null values. NULL is the default.

UNIQUE ( column constraint )

UNIQUE ( column_name [, ... ] ) ( table constraint )

The UNIQUE constraint specifies that a group of one or more columns of a table may contain only unique values. The behavior of the unique table constraint is the same as that for column constraints, with the additional capability to span multiple columns. For the purpose of a unique constraint, null values are not considered

equal. The column(s) that are unique must also contain all of the Greenplum distribution key column(s).

PRIMARY KEY ( column constraint ) 

PRIMARY KEY ( column_name [, ... ] ) ( table constraint )

The primary key constraint specifies that a column or columns of a table may contain only unique (non-duplicate), non-null values. Technically, PRIMARY KEY is

merely a combination of UNIQUE and NOT NULL, but identifying a set of columns as primary key also provides metadata about the design of the schema, as a primary key implies that other tables may rely on this set of columns as a unique identifier for rows. For a table to have a primary key, it must be hash distributed (not randomly distributed), and the primary key must contain all (or a superset) of the Greenplum distribution key column(s).

CHECK ( expression )

The CHECK clause specifies an expression producing a Boolean result which new or updated rows must satisfy for an insert or update operation to succeed. Expressions evaluating to TRUE or UNKNOWN succeed. Should any row of an insert or update operation produce a FALSE result an error exception is raised and the insert or update does not alter the database. A check constraint specified as a column constraint should reference that column’s value only, while an expression appearing in a table constraint may reference multiple columns. CHECK expressions cannot contain subqueries nor refer to variables other than columns of the current row.

WITH ( storage_option=value )

The WITH clause can be used to set storage options for the table or its indexes. Note that you can also set storage parameters on a particular partition or subpartition by declaring the WITH clause in the partition specification. The following storage options are available:

APPENDONLY - Set to TRUE to create the table as an append-only table. If FALSE or not declared, the table will be created as a regular heap-storage table.

ORIENTATION - Set to column for column-oriented storage, or row (the default) for row-oriented storage. This option is only valid if APPENDONLY=TRUE.

Heap-storage tables can only be row-oriented.

COMPRESSTYPE - Set to ZLIB (the default) or QUICKLZ to specify the type of compression used. QuickLZ uses less CPU power and compresses data faster at a

lower compression ratio than zlib. Conversely, zlib provides more compact compression ratios at lower speeds. This option is only valid if

APPENDONLY=TRUE.

COMPRESSLEVEL - For zlib compression of append-only tables, set to a value between 1 (fastest compression) to 9 (highest compression ratio). QuickLZ

compression level can only be set to 1. If not declared, the default is 0 (no compression). This option is only valid if APPENDONLY=TRUE.

FILLFACTOR - See CREATE INDEX for more information about this index storage parameter.

OIDS - Set to OIDS=FALSE (the default) so that rows do not have object identifiers assigned to them. Greenplum strongly recommends that you do not

enable OIDS when creating a table. On large tables, such as those in a typical Greenplum Database system, using OIDs for table rows can cause wrap-around of

the 32-bit OID counter. Once the counter wraps around, OIDs can no longer be assumed to be unique, which not only makes them useless to user applications, but

can also cause problems in the Greenplum Database system catalog tables. In addition, excluding OIDs from a table reduces the space required to store the table

on disk by 4 bytes per row, slightly improving performance. OIDS are not allowed on partitioned tables or append-only column-oriented tables.

ON COMMIT

The behavior of temporary tables at the end of a transaction block can be controlled using ON COMMIT. The three options are:

PRESERVE ROWS

No special action is taken at the ends of transactions for temporary tables. This is the default behavior.

DELETE ROWS All rows in the temporary table will be deleted at the end of each transaction block. Essentially, an automatic TRUNCATE is done at each commit.

DROP

The temporary table will be dropped at the end of the current transaction block.

TABLESPACE tablespace

The name of the tablespace in which the new table is to be created. If not specified, the database’s default tablespace is used.

USING INDEX TABLESPACE tablespace

This clause allows selection of the tablespace in which the index associated with a UNIQUE or PRIMARY KEY constraint will be created. If not specified, the database’s

default tablespace is used.

DISTRIBUTED BY (column, [ ... ] )

DISTRIBUTED RANDOMLY

Used to declare the Greenplum Database distribution policy for the table.  DISTIBUTED BY uses hash distribution with one or more columns declared as the

distribution key. For the most even data distribution, the distribution key should be the primary key of the table or a unique column (or set of columns). If that is not

possible, then you may choose DISTRIBUTED RANDOMLY, which will send the data round-robin to the segment instances. If not supplied, then hash distribution is

chosen using the PRIMARY KEY (if the table has one) or the first eligible column of the table as the distribution key.

PARTITION BY

Declares one or more columns by which to partition the table.

partition_type

Declares partition type: LIST (list of values) or RANGE (a numeric or date range).

partition_specification

Declares the individual partitions to create. Each partition can be defined individually or, for range partitions, you can use the EVERY clause (with a START

and optional END clause) to define an increment pattern to use to create the individual partitions.

DEFAULT PARTITION name - Declares a default partition. When data does not match to an existing partition, it is inserted into the default partition. Partition

designs that do not have a default partition will reject incoming rows that do not match to an existing partition.

PARTITION name - Declares a name to use for the partition. Partitions are created using the following naming convention:

parentname_level#_prt_givenname.

VALUES - For list partitions, defines the value(s) that the partition will contain.

START - For range partitions, defines the starting range value for the partition. By default, start values are INCLUSIVE. For example, if you declared a start date of

‘2008-01-01’, then the partition would contain all dates greater than or equal to ‘2008-01-01’. Typically the data type of the START expression is the same type

as the partition key column. If that is not the case, then you must explicitly cast to the intended data type.

END - For range partitions, defines the ending range value for the partition. By default, end values are EXCLUSIVE. For example, if you declared an end date of

‘2008-02-01’, then the partition would contain all dates less than but not equal to ‘2008-02-01’. Typically the data type of the END expression is the same type as

the partition key column. If that is not the case, then you must explicitly cast to the intended data type.

EVERY - For range partitions, defines how to increment the values from START to END to create individual partitions. Typically the data type of the EVERY

expression is the same type as the partition key column. If that is not the case, then you must explicitly cast to the intended data type.

WITH - Sets the table storage options for a partition. For example, you may want older partitions to be append-only tables and newer partitions to be regular heap

tables.

TABLESPACE - The name of the tablespace in which the partition is to be created. 

SUBPARTITION BY

Declares one or more columns by which to subpartition the first-level partitions of the table. The format of the subpartition specification is similar to that of a partition

specification described above.

SUBPARTITION TEMPLATE

Instead of declaring each subpartition definition individually for each partition, you can optionally declare a subpartition template to be used to create the subpartitions. This subpartition specification would then apply to all parent partitions.

Using OIDs in new applications is not recommended: where possible, using a SERIAL or other sequence generator as the table’s primary key is preferred. However, if your application does make use of OIDs to identify specific rows of a table, it is recommended to create a unique constraint on the OID column of that table, to ensure that OIDs in the table will indeed uniquely identify rows even after counter wrap-around. Avoid assuming that OIDs are unique across tables; if you need a database-wide unique identifier, use the combination of table OID and row OID for the purpose.

Greenplum Database has some special conditions for primary key and unique constraints with regards to columns that are the distribution key in a Greenplum table. For a unique constraint to be enforced in Greenplum Database, the table must be hash-distributed (not DISTRIBUTED RANDOMLY), and the constraint columns must be the same as (or a superset of) the table’s distribution key columns.

A primary key constraint is simply a combination of a unique constraint and a not-null constraint.

Greenplum Database automatically creates an index for each unique constraint or primary key constraint to enforce uniqueness. Thus, it is not necessary to create an index explicitly for primary key columns.

Foreign key constraints are not supported in Greenplum Database.

For inherited tables, unique constraints, primary key constraints, indexes and table privileges are not inherited in the current implementation.

Examples

1. Create a table named rank in the schema named baby and distribute the data using the columns rank, gender, and year:

CREATE TABLE baby.rank (id int, rank int, year smallint, gender char(1), count int ) DISTRIBUTED BY (rank, gender, year);

2. Create table films and table distributors (the primary key will be used as the Greenplum distribution key by default):

CREATE TABLE films (

code char(5) CONSTRAINT firstkey PRIMARY KEY,

title varchar(40) NOT NULL,

did integer NOT NULL,

date_prod date,

kind varchar(10),

len interval hour to minute

);

CREATE TABLE distributors (

did integer PRIMARY KEY DEFAULT nextval('serial'),

name varchar(40) NOT NULL CHECK (name <> '')

);

3. Create a gzip-compressed, append-only table:

CREATE TABLE sales (txn_id int, qty int, date date)

WITH (appendonly=true, compresslevel=5)

DISTRIBUTED BY (txn_id);

4. Create a three level partitioned table using subpartition templates and default partitions at each level:

CREATE TABLE sales (id int, year int, month int, day int, region text)

DISTRIBUTED BY (id)

PARTITION BY RANGE (year)

SUBPARTITION BY RANGE (month)

SUBPARTITION TEMPLATE (

START (1) END (13) EVERY (1),

DEFAULT SUBPARTITION other_months )

SUBPARTITION BY LIST (region)

SUBPARTITION TEMPLATE (

SUBPARTITION usa VALUES ('usa'),

SUBPARTITION europe VALUES ('europe'),

SUBPARTITION asia VALUES ('asia'),

DEFAULT SUBPARTITION other_regions)

( START (2002) END (2010) EVERY (1),

DEFAULT PARTITION outlying_years);

CREATE TABLE command conforms to the SQL standard, with the following exceptions:

•Temporary Tables — In the SQL standard, temporary tables are defined just once and automatically exist (starting with empty contents) in every session that needs them. Greenplum Database instead requires each session to issue its own CREATE TEMPORARY TABLE command for each temporary table to be used. This allows different sessions to use the same temporary table name for different purposes, whereas the standard’s approach constrains all instances of a given temporary table name to have the same table structure.

The standard’s distinction between global and local temporary tables is not in Greenplum Database. Greenplum Database will accept the GLOBAL and LOCAL keywords in a temporary table declaration, but they have no effect.

If the ON COMMIT clause is omitted, the SQL standard specifies that the default behavior as ON COMMIT DELETE ROWS. However, the default behavior in Greenplum Database is ON COMMIT PRESERVE ROWS. The ON COMMIT DROP option does not exist in the SQL standard.

•Column Check Constraints — The SQL standard says that CHECK column constraints may only refer to the column they apply to; only CHECK table constraints may refer to multiple columns. Greenplum Database does not enforce this restriction; it treats column and table check constraints alike.

•NULL Constraint — The NULL constraint is a Greenplum Database extension to the SQL standard that is included for compatibility with some other database systems (and for symmetry with the NOT NULL constraint). Since it is the default for any column, its presence is not required.

•Inheritance — Multiple inheritance via the INHERITS clause is a Greenplum Database language extension. SQL:1999 and later define single inheritance using a different syntax and different semantics. SQL:1999-style inheritance is not yet supported by Greenplum Database.

•Partitioning — Table partitioning via the PARTITION BY clause is a Greenplum Database language extension.

•Zero-column tables — Greenplum Database allows a table of no columns to be created (for example, CREATE TABLE foo();). This is an extension from the SQL standard, which does not allow zero-column tables. Zero-column tables are not in themselves very useful, but disallowing them creates odd special cases for ALTER TABLE DROP COLUMN, so Greenplum decided to ignore this spec restriction.

•WITH clause — The WITH clause is a Greenplum Database extension; neither storage parameters nor OIDs are in the standard.

•Tablespaces — The Greenplum Database concept of tablespaces is not part of the SQL standard. The clauses TABLESPACE and USING INDEX TABLESPACE are extensions.

•Data Distribution — The Greenplum Database concept of a parallel or distributed database is not part of the SQL standard. The DISTRIBUTED clauses are extensions.