Re: table aliases save time when parsing??

From: Igor Neyman <ineyman_at_perceptron.com>
Date: Tue, 10 Jul 2001 05:57:04 -0700
Message-ID: <F001.003454F9.20010710052610@fatcity.com>

Well, it's not aliases themselves, but the practice of using aliases as prefixes, when referring to columns:

SELECT t1.col1, t1.col2, t2.col1
FROM table1 t1, table2 t2
WHERE t1.col2 = t2.col2

that's what saves time when parsing: this way you tell the parser which table column list to look for, otherwise (when no prefixes used) it has to search through all tables column lists for particular column definition (and also to make sure, that this column name is unique in all column lists - if not you'll be getting an error, if not using prefixes).

But, you can get the same result (save time on parsing), when using table names as prefixes:

SELECT table1.col1, table1.col2, table2.col1 FROM table1, table2
WHERE table1.col2 = table2.col2

It's just that aliases are usually short (while table names could be long), and it's easier to read the code.

List, please correct me, if I'm wrong.

Igor Neyman, OCP DBAPerceptron, Inc.(734)414-4627<A href="mailto:ineyman_at_perceptron.com">ineyman_at_perceptron.com

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Sent: Tuesday, July 10, 2001 7:10
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Subject: table aliases save time when parsing??

  Hi,
    was reading
  CorrelatedSubqueries.pdf from
  oriole corp.
  In fact it's good programming
  practice to use aliases in every situation where more than one table is   referred to in a statement, since it saves time when <FONT   face="Times New Roman" size=3>parsin<FONT   face="Times New Roman" size=3>g.

  Can some one please explain how it
  helps?

  cozI am anoviceOracle Certifiable
  DBBS Received on Tue Jul 10 2001 - 07:57:04 CDT