Re: Does the case of an Oracle query statement affect query perfo

[Tim Gorman]

All that he is referring to is the possibility that "mixing-n-matching" will cause the same SQL statement to be hashed differently, thus stored individually in the Shared SQL Area cache, thus more "hard parses" unnecessarily.  More "hard-parses" is indeed "more work"...   Though technically correct, there are many steps between someone coding a SQL statement and this end-result of additional hard-parses... If a developer or end-user is working via a precompiler/interpreter such as PRO*C, SQLJ, or PL/SQL or many other reporting tools, then the upper- and lower-case issues will be largely made irrelevant as the precompiler/interpreter tends to set all SQL command-text some similar convention before passing to the RDBMS (i.e. all upper-case and remove all unnecessary white-space, etc)... If it is not SQL developers writing this SQL into program-modules but instead end-users working interactively, then you have to ask yourself how many times they can type in and execute SQL in order for the increased number of "hard-parses" to matter.  Assume 200 ad-hoc interactive end-user sessions, each typing in and executing slightly different SQL 20 times per day.  That's 4000 more "hard-parses" -- no big deal... There are likely more circumstances to consider...   However, if the people doing this coding are developers working in a low-level API such as OCI (i.e. C or C++), DBI::DBD (i.e. Perl), or JDBC (i.e. Java), then this SQL text will be sent straight to the RDBMS parser where it will indeed cause additional hard-parses.  Since this code might be embedded inside a high-concurrency application, this problem could grow quite serious, especially if the developers follow-up this particular "bad habit" with other bad habits such as embedded literal data values, etc...   As always, the severity of the problem is dependent on specific circumstances.  It could be no problem at all, it could be the harbinger for serious problems... ----- Original Message ----- From: Mercadante, Thomas F To: Multiple recipients of list ORACLE-L Sent: Monday, September 30, 2002 7:48 AM Subject: RE: Does the case of an Oracle query statement affect query perfo Raj,   Do you have any test cases or white papers to support your statement?  Especially the part about   "if you mix-n-match that will make Oracle do more work."   never heard of this before and I am interested if it is true. Tom Mercadante Oracle Certified Professional -----Original Message----- From: Jamadagni, Rajendra [mailto:[EMAIL PROTECTED]] Sent: Monday, September 30, 2002 8:33 AM To: Multiple recipients of list ORACLE-L Subject: RE: Does the case of an Oracle query statement affect query perfo As long as you stick to either (a) or (b) you will be okay ... if you mix-n-match that will make Oracle do more work.   Raj ______________________________________________________ Rajendra Jamadagni              MIS, ESPN Inc. Rajendra dot Jamadagni at ESPN dot com Any opinion expressed here is personal and doesn't reflect that of ESPN Inc. QOTD: Any clod can have facts, but having an opinion is an art! -----Original Message----- From: Shantanu Datta [mailto:[EMAIL PROTECTED]] Sent: Monday, September 30, 2002 3:58 AM To: Multiple recipients of list ORACLE-L Subject: Does the case of an Oracle query statement affect query performance? Hi,     Pardon me for such a naive question, coz I am a novice when it comes to Oracle. This is basically got to do with how Oracle parses a query.       Consider the following queries:   a)    SELECT column1, column2 FROM table WHERE column0 = 5;   b)    SELECT COLUMN1, COLUMN2 FROM TABLE WHERE COLUMN0 =5;       Scenario 1: I use the naming convention a) for ALL my queries       Scenario 2: I use the naming convention b) for ALL my queries       Will there be any difference in the execution time of the same queries in Scenario 1 vs 2?     Thanx in advance, Shantanu. --------------