"Martijn Tonies" <m.tonies@stripped> wrote on 11/11/2005 03:42:42 AM:
>
> > > Does MySQL support:
> > >
> > > SELECT ID_TAG= ID
> > > FROM TABLE
> > >
> > > rather than select ID TAG_ID from Table. I need this for MS SQL
> > Compabilty.
> > >
> > >
> >
> >
> > Within the SELECT statement you must use := If you were in a SET
> > statement, you could use = or :=
> >
> > http://dev.mysql.com/doc/refman/4.1/en/variables.html
>
> Shawn, I'm unsure if this is the same.
>
> In MS SQL, using the above construct defines a column alias.
>
> With regards,
>
> Martijn Tonies
> Database Workbench - tool for InterBase, Firebird, MySQL, Oracle & MS
SQL
> Server
> Upscene Productions
> http://www.upscene.com
> Database development questions? Check the forum!
> http://www.databasedevelopmentforum.com
>
>
Did you read the link?
The OP wanted to know if MySQL supported the = sign in a SELECT statement.
The documentaion I referred the OP to clearly differentiates the use of =
and := within SELECT statements and SET statements for MySQL. If the MySQL
behavior is not what they were hoping for then they are now informed that
a form used in MS SQL to produce column aliases does not work the same way
on MySQL platform and why it doesn't work that way. I don't think I could
have explained it myself any better than what was already documented.
Hence, the simple RTFM answer....
BTW -- the "SELECT ID TAG_ID,..." form works equally well on MS SQL to
produce column aliases because it is ANSI compliant.
From: "ISO/IEC 9075-2:2003 (E) 7.12 <query specification>" (a.k.a.
SQL:2003's definition of the SELECT clause)
--------------quote-----------------------
<query specification> ::=
SELECT [ <set quantifier> ] <select list> <table expression>
<select list> ::=
<asterisk>
| <select sublist> [ { <comma> <select sublist> }... ]
<select sublist> ::=
<derived column>
| <qualified asterisk>
<qualified asterisk> ::=
<asterisked identifier chain> <period> <asterisk>
| <all fields reference>
<asterisked identifier chain> ::=
<asterisked identifier> [ { <period> <asterisked identifier> }... ]
<asterisked identifier> ::= <identifier>
<derived column> ::= <value expression> [ <as clause> ]
<as clause> ::= [ AS ] <column name>
<all fields reference> ::=
<value expression primary> <period> <asterisk>
[ AS <left paren> <all fields column name list> <right paren> ]
<all fields column name list> ::= <column name list>
--------------end quote-----------------------
As you can see, there is no grammar for the "ALIAS=FIELDNAME" form
supported by MS SQL. Aliases are not defined with the = symbol. <value
expression>s can contain = signs. However if used un-aliased, the
resulting column is the entire expression not just what is on the
left-hand-side of the = sign in the expression. Once again, MS's inability
to follow simple directions has created headaches for its users.
Respectfully,
Shawn Green
Database Administrator
Unimin Corporation - Spruce Pine
