Sponsored Content
Top Forums Shell Programming and Scripting Select record with MAX value in MySQL Post 302433402 by pludi on Tuesday 29th of June 2010 01:03:20 PM
Old 06-29-2010
It's been a while since I've spoken MySQL... but I'd do it this way
Code:
CREATE UNIQUE INDEX IX_uploaded_name_time ON uploaded ( file_name, file_time )

But the ALTER TABLE syntax (the first one) should get you the same result. If not, you can always drop and re-create the index.

It would be interesting tho to see the comparison of the execution timing and EXPLAIN plan with and without the indices.

And if you want to optimize further, here's an article on how to use the MySQL profiler.
This User Gave Thanks to pludi For This Post:
 

9 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Select Record based on First Column

Hi, I have a file with multiple records...and I have to select records based on first column....here is the sample file... I01,abc,125,1a2,LBVI02 I01,abc,126,2b5,LBVI02 I02,20070530,254,abc,LLBI01 I02,20070820,111,bvd,NGBI01 I need all records with I01 in first field in one file and... (8 Replies)
Discussion started by: mgirinath
8 Replies

2. Shell Programming and Scripting

mysql select query optimization..

hi.. i need to optimize my select query .. my situation is like this .. i have 15 lac recors in my table.. the following query takes nine seconds to give the required output.. SELECT max(ah.AUC_AMT), SUBSTRING_INDEX(GROUP_CONCAT(SUBSTRING_INDEX(ah.AUC_CUS_NAME,'@',1) order by AUC_AMT... (0 Replies)
Discussion started by: senkerth
0 Replies

3. UNIX for Advanced & Expert Users

mysql select query optimization..

hi.. i need to optimize my select query .. my situation is like this .. i have 15 lac recors in my table.. the following query takes nine seconds to give the required output.. SELECT max(ah.AUC_AMT), SUBSTRING_INDEX(GROUP_CONCAT(SUBSTRING_INDEX(ah.AUC_CUS_NAME,'@',1) order by AUC_AMT... (1 Reply)
Discussion started by: senkerth
1 Replies

4. UNIX for Dummies Questions & Answers

Select max value based on filename

Hi, I would just like to know how to get the file with the max filename on a directory and get rid of all the others. For example, in directory A:/ i have the ff files: APPLE2001 APPLE2002 APPLE2003 GRAPE2004 what I want to get is the max in files whose filenames start with APPLE*,... (4 Replies)
Discussion started by: madden
4 Replies

5. Shell Programming and Scripting

Max value Record from a File

I have a file with 3 columns I want to get the record with the max salary. If there are more than 1 record having the highest salary, i want any one of them. empid,ename,Sal 1,abc,100 2,def,200 3,xyz,300 4,pqr,100 5,mnq,300 Output Any record with 300 as salary Please use next... (1 Reply)
Discussion started by: traininfa
1 Replies

6. Programming

Getting Rows from a MySQL Table with max values?

I feel stupid for asking this because it seems that MYSQL code isn't working the way that I think it should work. Basically I wrote code like this: select * from `Test_DC_Trailer` HAVING max(DR_RefKey); Where the DR_RefKey is a unique numeric field that is auto iterated (like a primary key)... (7 Replies)
Discussion started by: Astrocloud
7 Replies

7. Shell Programming and Scripting

Select record having different value in second column

I want records which have more than one and different value in the second column on the below sample file. Ex, I have the samle file below :- XYZ 1 XYZ 3 abc 1 abc 1 qwe 2 qwe 1 qwe 3 I want to select XYZ and QWE line only. (6 Replies)
Discussion started by: Sanjeev Yadav
6 Replies

8. Programming

MySQL select user with the same IP address

Dear community, I woul like to make a query to output all the users having the same IP address. The table is somethig like: name logged_ip ==== ========= user1 127.0.0.1 user2 127.0.0.2 user3 127.0.0.3 user4 127.0.0.1 user5 127.0.0.2 user6 127.0.0.5I used this query... (4 Replies)
Discussion started by: Lord Spectre
4 Replies

9. Shell Programming and Scripting

Script to record max memory usage of program

Hello, I am working on an application that uses allot of memory depending on the input. I am also working on more than one processing algorithm. The program has a long processing time (hours) so it would be nice to be able to monitor the maximum memory footprint of the application during runs... (1 Reply)
Discussion started by: LMHmedchem
1 Replies
SQL::Translator::Parser::MySQL(3pm)			User Contributed Perl Documentation		       SQL::Translator::Parser::MySQL(3pm)

NAME
SQL::Translator::Parser::MySQL - parser for MySQL SYNOPSIS
use SQL::Translator; use SQL::Translator::Parser::MySQL; my $translator = SQL::Translator->new; $translator->parser("SQL::Translator::Parser::MySQL"); DESCRIPTION
The grammar is influenced heavily by Tim Bunce's "mysql2ora" grammar. Here's the word from the MySQL site (http://www.mysql.com/doc/en/CREATE_TABLE.html): CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name [(create_definition,...)] [table_options] [select_statement] or CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name LIKE old_table_name; create_definition: col_name type [NOT NULL | NULL] [DEFAULT default_value] [AUTO_INCREMENT] [PRIMARY KEY] [reference_definition] or PRIMARY KEY (index_col_name,...) or KEY [index_name] (index_col_name,...) or INDEX [index_name] (index_col_name,...) or UNIQUE [INDEX] [index_name] (index_col_name,...) or FULLTEXT [INDEX] [index_name] (index_col_name,...) or [CONSTRAINT symbol] FOREIGN KEY [index_name] (index_col_name,...) [reference_definition] or CHECK (expr) type: TINYINT[(length)] [UNSIGNED] [ZEROFILL] or SMALLINT[(length)] [UNSIGNED] [ZEROFILL] or MEDIUMINT[(length)] [UNSIGNED] [ZEROFILL] or INT[(length)] [UNSIGNED] [ZEROFILL] or INTEGER[(length)] [UNSIGNED] [ZEROFILL] or BIGINT[(length)] [UNSIGNED] [ZEROFILL] or REAL[(length,decimals)] [UNSIGNED] [ZEROFILL] or DOUBLE[(length,decimals)] [UNSIGNED] [ZEROFILL] or FLOAT[(length,decimals)] [UNSIGNED] [ZEROFILL] or DECIMAL(length,decimals) [UNSIGNED] [ZEROFILL] or NUMERIC(length,decimals) [UNSIGNED] [ZEROFILL] or CHAR(length) [BINARY] or VARCHAR(length) [BINARY] or DATE or TIME or TIMESTAMP or DATETIME or TINYBLOB or BLOB or MEDIUMBLOB or LONGBLOB or TINYTEXT or TEXT or MEDIUMTEXT or LONGTEXT or ENUM(value1,value2,value3,...) or SET(value1,value2,value3,...) index_col_name: col_name [(length)] reference_definition: REFERENCES tbl_name [(index_col_name,...)] [MATCH FULL | MATCH PARTIAL] [ON DELETE reference_option] [ON UPDATE reference_option] reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT table_options: TYPE = {BDB | HEAP | ISAM | InnoDB | MERGE | MRG_MYISAM | MYISAM } or ENGINE = {BDB | HEAP | ISAM | InnoDB | MERGE | MRG_MYISAM | MYISAM } or AUTO_INCREMENT = # or AVG_ROW_LENGTH = # or [ DEFAULT ] CHARACTER SET charset_name or CHECKSUM = {0 | 1} or COLLATE collation_name or COMMENT = "string" or MAX_ROWS = # or MIN_ROWS = # or PACK_KEYS = {0 | 1 | DEFAULT} or PASSWORD = "string" or DELAY_KEY_WRITE = {0 | 1} or ROW_FORMAT= { default | dynamic | fixed | compressed } or RAID_TYPE= {1 | STRIPED | RAID0 } RAID_CHUNKS=# RAID_CHUNKSIZE=# or UNION = (table_name,[table_name...]) or INSERT_METHOD= {NO | FIRST | LAST } or DATA DIRECTORY="absolute path to directory" or INDEX DIRECTORY="absolute path to directory" A subset of the ALTER TABLE syntax that allows addition of foreign keys: ALTER [IGNORE] TABLE tbl_name alter_specification [, alter_specification] ... alter_specification: ADD [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name,...) [reference_definition] A subset of INSERT that we ignore: INSERT anything ARGUMENTS
This parser takes a single optional parser_arg "mysql_parser_version", which provides the desired version for the target database. Any statement in the processed dump file, that is commented with a version higher than the one supplied, will be stripped. The default "mysql_parser_version" is set to the conservative value of 40000 (MySQL 4.0) Valid version specifiers for "mysql_parser_version" are listed here More information about the MySQL comment-syntax: <http://dev.mysql.com/doc/refman/5.0/en/comments.html> AUTHOR
Ken Youens-Clark <kclark@cpan.org>, Chris Mungall <cjm@fruitfly.org>. SEE ALSO
Parse::RecDescent, SQL::Translator::Schema. perl v5.14.2 2012-05-01 SQL::Translator::Parser::MySQL(3pm)
All times are GMT -4. The time now is 07:41 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy