A Basic Question with MS SQL Help

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A Basic Question with MS SQL Help

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a_r_satish
Yak Posting Veteran

84 Posts

Posted - 2006-02-09 : 23:11:23

Hello all,

This is a very basic question. Probably some of the newbie may find this difficulty.

As we know there is help facility provided with the MS-SQL. But i find it very difficult to understand the thing that are mentioned there.
For example, when i want to alter a table then the syntax provided is as,
ALTER TABLE table
{ [ ALTER COLUMN column_name
{ new_data_type [ ( precision [ , scale ] ) ]
[ COLLATE < collation_name > ]
[ NULL | NOT NULL ]
| {ADD | DROP } ROWGUIDCOL }
]
| ADD
{ [ < column_definition > ]
| column_name AS computed_column_expression
} [ ,...n ]
| [ WITH CHECK | WITH NOCHECK ] ADD
{ < table_constraint > } [ ,...n ]
| DROP
{ [ CONSTRAINT ] constraint_name
| COLUMN column } [ ,...n ]
| { CHECK | NOCHECK } CONSTRAINT
{ ALL | constraint_name [ ,...n ] }
| { ENABLE | DISABLE } TRIGGER
{ ALL | trigger_name [ ,...n ] }
}

< column_definition > ::=
{ column_name data_type }
[ [ DEFAULT constant_expression ] [ WITH VALUES ]
| [ IDENTITY [ (seed , increment ) [ NOT FOR REPLICATION ] ] ]
]
[ ROWGUIDCOL ]
[ COLLATE < collation_name > ]
[ < column_constraint > ] [ ...n ]

< column_constraint > ::=
[ CONSTRAINT constraint_name ]
{ [ NULL | NOT NULL ]
| [ { PRIMARY KEY | UNIQUE }
[ CLUSTERED | NONCLUSTERED ]
[ WITH FILLFACTOR = fillfactor ]
[ ON { filegroup | DEFAULT } ]
]
| [ [ FOREIGN KEY ]
REFERENCES ref_table [ ( ref_column ) ]
[ ON DELETE { CASCADE | NO ACTION } ]
[ ON UPDATE { CASCADE | NO ACTION } ]
[ NOT FOR REPLICATION ]
]
| CHECK [ NOT FOR REPLICATION ]
( logical_expression )
}

< table_constraint > ::=
[ CONSTRAINT constraint_name ]
{ [ { PRIMARY KEY | UNIQUE }
[ CLUSTERED | NONCLUSTERED ]
{ ( column [ ,...n ] ) }
[ WITH FILLFACTOR = fillfactor ]
[ ON {filegroup | DEFAULT } ]
]
| FOREIGN KEY
[ ( column [ ,...n ] ) ]
REFERENCES ref_table [ ( ref_column [ ,...n ] ) ]
[ ON DELETE { CASCADE | NO ACTION } ]
[ ON UPDATE { CASCADE | NO ACTION } ]
[ NOT FOR REPLICATION ]
| DEFAULT constant_expression
[ FOR column ] [ WITH VALUES ]
| CHECK [ NOT FOR REPLICATION ]
( search_conditions )
}

Too hard to understand.
can anyone help and suggest what it actually mean???

Thanks in advance.

Regards,
satish.r

jen
Master Smack Fu Yak Hacker

4110 Posts

Posted - 2006-02-10 : 01:26:01

i just knew there was some use for that subject (theory of computation)

what you see is called a definition, syntax, regular expression in words

anything enclosed in [ ] is optional,
a | denotes a choice
a { denotes 0 or more repetitions of the definition within
words in upper case are keywords or reserved words
... means a range
<text>::= 'text' is the one being defined

HTH

--------------------
keeping it simple...

khtan
In (Som, Ni, Yak)

17689 Posts

Posted - 2006-02-10 : 01:31:27

refer to Transact-SQL Reference - Transact-SQL Syntax Conventions in Books Online

----------------------------------
'KH'
everything that has a beginning has an end

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