3.12 Data Type Declaration Syntax

This section documents the syntax of declaring data types. Data type declaration commonly occurs in DDL statements, but also in CAST and EXECUTE BLOCK.

The syntax documented below is referenced from other parts of this language reference.

3.12.1 Scalar Data Types Syntax

The scalar data types are simple data types that hold a single value. For reasons of organisation, the syntax of BLOB types are defined separately in Section 3.12.2, BLOB Data Types Syntax.

Scalar Data Types Syntax

<domain_or_non_array_type> ::=
    <scalar_datatype>
  | <blob_datatype>
  | [TYPE OF] domain
  | TYPE OF COLUMN rel.col
 
<scalar_datatype> ::=
    SMALLINT | INT[EGER] | BIGINT | INT128
  | REAL | FLOAT [(bin_prec)] | DOUBLE PRECISION
  | DECFLOAT [(dec_prec)]
  | BOOLEAN
  | DATE | TIME | TIMESTAMP
  | {DECIMAL | NUMERIC} [(precision [, scale])]
  | {VARCHAR | {CHAR | CHARACTER} VARYING} (length)
    [CHARACTER SET charset]
  | {CHAR | CHARACTER} [(length)] [CHARACTER SET charset]
  | {NCHAR | NATIONAL {CHARACTER | CHAR}} VARYING (length)
  | {NCHAR | NATIONAL {CHARACTER | CHAR}} [(length)]
  | BINARY [(length)]
  | {VARBINARY | BINARY VARYING} (length)

Table 3.12.1.1 Arguments for the Scalar Data Types Syntax

3.12.1.1 Use of Domains in Declarations

A domain name can be specified as the type of a PSQL parameter or local variable. The parameter or variable will inherit all domain attributes. If a default value is specified for the parameter or variable, it overrides the default value specified in the domain definition.

If the TYPE OF clause is added before the domain name, only the data type of the domain is used: any of the other attributes of the domain — NOT NULL constraint, CHECK constraints, default value — are neither checked nor used. However, if the domain is of a text type, its character set and collation sequence are always used.

3.12.1.2 Use of Column Type in Declarations

Input and output parameters or local variables can also be declared using the data type of columns in existing tables and views. The TYPE OF COLUMN clause is used for that, specifying relationname.columnname as its argument.

When TYPE OF COLUMN is used, the parameter or variable inherits only the data type and — for string types — the character set and collation sequence. The constraints and default value of the column are ignored.

3.12.2 BLOB Data Types Syntax

The BLOB data types hold binary, character or custom format data of unspecified size. For more information, see Section 3.7, Binary Data Types.

BLOB Data Types Syntax

<blob_datatype> ::=
    BLOB [SUB_TYPE {subtype_num | subtype_name}]
    [SEGMENT SIZE seglen] [CHARACTER SET charset]
  | BLOB [(seglen [, subtype_num])]

Table 3.12.2.1 Arguments for the Blob Data Types Syntax

3.12.3 Array Data Types Syntax

The array data types hold multiple scalar values in a single or multi-dimensional array. For more information, see Section 3.8, Array Types

Array Data Types Syntax

<array_datatype> ::=
    {SMALLINT | INT[EGER] | BIGINT | INT128} <array_dim>
  | {REAL | FLOAT [(bin_prec)] | DOUBLE PRECISION} <array_dim>
  | DECFLOAT [(dec_prec)]
  | BOOLEAN <array_dim>
  | {DATE | TIME | TIMESTAMP} <array_dim>
  | {DECIMAL | NUMERIC} [(precision [, scale])] <array_dim>
  | {VARCHAR | {CHAR | CHARACTER} VARYING} (length)
    <array_dim> [CHARACTER SET charset]
  | {CHAR | CHARACTER} [(length)] <array_dim>
    [CHARACTER SET charset]
  | {NCHAR | NATIONAL {CHARACTER | CHAR}} VARYING (length)
    <array_dim>
  | {NCHAR | NATIONAL {CHARACTER | CHAR}}
    [(length)] <array_dim>
  | BINARY [(length)] <array_dim>
  | {VARBINARY | BINARY VARYING} (length) <array_dim>
 
<array_dim> ::= '[' [m:]n [,[m:]n ...] ']'

Table 3.12.3.1 Arguments for the Array Data Types Syntax