It's been a while since I've spoken MySQL... but I'd do it this way
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.
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)
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)
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)
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)
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)
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)
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)
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)
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
LEARN ABOUT DEBIAN
grass-mysql
grass-mysql(1grass) Grass User's Manual grass-mysql(1grass)NAME
grass-mysql - MySQL driver
MySQL driver MySQL driver in GRASS MySQL database driver in GRASS enables GRASS to store vector attributes in MySQL server.
Because vector attribute tables are created automaticaly when a new vector is written and the name of the table is the same as the name of
the vector it is good practice to create a new database for each GRASS mapset.
Creating a MySQL database
A new database is created within MySQL:
mysql> CREATE DATABASE mydb;
See the MySQL manual for details.
Driver and database name
GRASS modules require 2 parameters to connect to a database. Those parameters are 'driver' and 'database'. For MySQL driver the parameter
'driver' should be set to value 'mysql'. The parameter 'database' can be given in two formats:
Database name - in case of connection from localhost
String of comma separated list of kye=value options. Supported options are:
dbname - database name
host - host name or IP address
port - server port number
Examples of connection parameters:
db.connect driver=mysql database=mytest
db.connect driver=mysql database='dbname=mytest,host=test.grass.org'
Data types
GRASS supports almost all MySQL data types with following limitations:
Binary columns (BINARY, VARBINARY, TINYBLOB, MEDIUMBLOB, BLOB, LONGBLOB) are not not supported. If a table with binary col-
umn(s) is used in GRASS a warning is printed and only the supported columns are returned in query results.
Columns of type SET and ENUM are represented as string (VARCHAR).
Very large integers in columns of type BIGINT can be lost or corrupted because GRASS does not support 64 bin integeres on
most platforms.
GRASS does not currently distinguish types TIMESTAMP and DATETIME. Both types are in GRASS interpreted as TIMESTAMP.
Indexes
GRASS modules automaticaly create index on key column of vector attributes table. The index on key column is important for performance of
modules which update the attribute table, for example v.to.db, v.distance and v.what.rast.
Privileges
Because MySQL does not support groups of users and because only MySQL 'root' can grant privileges to other users GRASS cannot automaticaly
grant select privileges on created tables to group of users.
If you want to give privilege to read data from your mapset to other users you have to ask your MySQL server administrator to grant select
privilege to them on the MySQL database used for that mapset. For example, to allow everybody to read data in from your database 'mydb':
shell> mysql --user=root mysql
mysql> GRANT SELECT ON mydb.* TO ''@'%';
Schemas
Because MySQL does not support database schemas the parameter 'schema' of module db.connect should never be set to any value. If you set
that parameter for MySQL driver GRASS will try to write tables to the specified schema which will result in errors.
Groups
MySQL does not support user groups. Any settings specified by 'group' parameter of module db.connect are ignored by GRASS for MySQL driver.
SEE ALSO
db.connect, SQL support in GRASS GIS
Credits
Development of the driver was sponsored by Faunalia (Italy) as part of a project for ATAC.
AUTHOR
Radim Blazek
Last changed: $Date: 2011-02-07 18:59:50 +0100 (Mon, 07 Feb 2011) $
Help Index
GRASS 6.4.2grass-mysql(1grass)