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SET NULL Command

  • Artikkeli

Determines how null values are supported by the ALTER TABLE - SQL, CREATE TABLE - SQL, and INSERT - SQL commands.

Syntax

  
SET NULL ON | OFF

Arguments

ON
(Default for the driver; the default for Visual FoxPro is OFF.) Specifies that all columns in a table created with ALTER TABLE and CREATE TABLE will allow null values. You can override null value support for columns in the table by including the NOT NULL clause in the columns' definitions.

Also specifies that INSERT - SQL will insert null values into any columns not included in the INSERT - SQL VALUE clause. INSERT - SQL will insert null values only into columns that allow null values.

OFF
Specifies that all columns in a table created with ALTER TABLE and CREATE TABLE will not allow null values. You can designate null value support for columns in ALTER TABLE and CREATE TABLE by including the NULL clause in the columns' definitions.

Also specifies that INSERT - SQL will insert blank values into any columns not included in the INSERT - SQL VALUE clause.

Remarks

SET NULL affects only how null values are supported by ALTER TABLE, CREATE TABLE, and INSERT - SQL. Other commands are unaffected by SET NULL.

See Also

ALTER TABLE - SQL Command
CREATE TABLE - SQL Command
INSERT - SQL Command