SQL$HELP72.HLB  —  ALTER  DOMAIN  Arguments

1  –  char-data-types 

    A valid SQL character data type. For more information on
    character data types, see the Data_Types HELP topic.

2  –  character-set-name 

    A valid character set name. For a list of allowable character set
    names, see the Supported_Character_Sets HELP topic.

3  –  COLLATING_SEQUENCE 

    Specifies a new collating sequence for the named domain.

    The OpenVMS National Character Set (NCS) utility provides a
    set of predefined collating sequences and also lets you define
    collating sequences of your own. The COLLATING SEQUENCE clause
    accepts both predefined and user-defined NCS collating sequences.

    Before you use the COLLATING SEQUENCE clause in an ALTER DOMAIN
    statement, you must first specify the NCS collating sequence for
    SQL using the CREATE COLLATING SEQUENCE statement. The sequence
    name argument in the COLLATING SEQUENCE clause must be the same
    as the sequence name in the CREATE COLLATING SEQUENCE statement.

4  –  COMMENT_IS 

    Adds a comment about the domain. SQL displays the text of the
    comment when it executes a SHOW DOMAIN statement. Enclose the
    comment in single quotation marks ( ') and separate multiple
    lines in a comment with a slash mark (/).

5  –  date-time-data-types 

    A data type that specifies a date, time, or interval. For more
    information on date-time data types, see the Data_Types HELP
    topic.

6  –  DEFAULT value-expr 

    Provides a default value for a domain.

    You can use any value expression including subqueries,
    conditional, character, date/time, and numeric expressions as
    default values. See Value Expressions for more information about
    value expressions.

    For more information about NULL, see the NULL_Keyword HELP topic.

    The value expressions described in Value Expressions include
    DBKEY and aggregate functions. However, the DEFAULT clause is
    not a valid location for referencing a DBKEY or an aggregate
    function. If you attempt to reference either, you receive a
    compile-time error.

    If you do not specify a DEFAULT for a column, it inherits the
    DEFAULT from the domain. If you do not specify a default for
    either the column or domain, SQL assigns NULL as the default
    value.

7  –  domain-constraint 

    Adds or modifies a constraint for the existing named domain.

    Domain constraints specify that columns based on the domain
    contain only certain data values or that data values can or
    cannot be null.

    Use the CHECK clause to specify that a value must be within a
    specified range or that it matches a list of values. When you
    specify a CHECK clause for a domain constraint, you ensure that
    all values stored in columns based on the domain are checked
    consistently.

    To refer to the values of all columns of a domain constraint, use
    the VALUE keyword. For example:

    SQL> CREATE DOMAIN dom1 CHAR(1)
    cont> CHECK (VALUE IN ('F','M'))
    cont> NOT DEFERRABLE;

    For any dialect other than SQL99, SQL92, ORACLE LEVEL 1 or
    ORACLE LEVEL 2, you must specify that domain constraints are
    NOT DEFERRABLE.

    When you add (or modify) a domain constraint, SQL propagates
    the new constraint definition to all the columns that are based
    on the domain. If columns that are based on the domain contain
    data that does not conform to the constraint, SQL returns the
    following error:

    %RDB-E-NOT_VALID, validation on field DATE_COL caused operation to fail

8  –  domain-name 

    The name of a domain you want to alter. The domain name must be
    unique among domain names in the database.

9  –  DROP_DEFAULT 

    Deletes (drops) the default value of a domain.

10  –  IS datatype 

    A valid SQL data type. For more information on data types, see
    the Data_Types HELP topic.

11  –  NO_COLLATING_SEQUENCE 

    Specifies that the named domain uses the standard default
    collating sequence, that is, ASCII. Use the NO COLLATING SEQUENCE
    clause to override the collating sequence defined for the schema
    in the CREATE SCHEMA or ALTER SCHEMA statement, or the domain in
    the CREATE DOMAIN statement.

12  –  RENAME_TO 

    Changes the name of the domain being altered. See the RENAME for
    further discussion. If the new name is the name of a synonym then
    an error will be raised.

    The RENAME TO clause requires synonyms be enabled for this
    database. Refer to the ALTER DATABASE statement SYNONYMS ARE
    ENABLED clause. Note that these synonyms may be deleted if they
    are no longer used by database definitions or applications.

13  –  SET_DEFAULT 

    Provides a default value for a column if the row that is inserted
    does not include a value for that column. A column default
    value overrides a domain default value. If you do not specify
    a default value, SQL assigns NULL as the default value. For more
    information about NULL, see the NULL_Keyword HELP topic.

14  –  sql-and-dtr-clause 

    Optional SQL and DATATRIEVE formatting clause. For more
    information on the formatting clauses, see the DATATRIEVE HELP
    topic.

15  –  value-expr 

    Specifies the default value of a domain.
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