Tagged Questions

0
votes
2answers
32 views

how important are mysql's innodb logs?

I'm basically concerned about the following two settings, these are my default settings : innodb_log_buffer_size 1048576 innodb_log_file_size 5242880 I haven't changed them for 2 reasons : one, ...
0
votes
3answers
52 views

Using MySQL InnoDB as an Archive

My site has a main MySQL InnoDB table that it does most of its work on. New rows get inserted at a rate of 1 million per week, and rows older than a week gets moved over to an archive table on a daily ...
0
votes
1answer
206 views

How to UPDATE a column to SET previous row value to NULL cells?

I have a table as id value 1 music 2 3 movie 4 5 6 book 7 8 Some values are missing, and I want to assign the value of previous row to produce id value 1 music 2 music 3 movie 4 ...
3
votes
2answers
241 views

How to split a string to and get info from another table in mysql

I have a system to assign score for each sentence stored in a column: TABLE 1: word_scores word score this 3 is 4 a 5 test 1 another 0 sentence 8 TABLE 2: ...
3
votes
2answers
173 views

How to concatenate a column after x rows?

I have a table with columns object varchar(255), frequency tinyint(3) unsigned, I want to concatenate the objects if the sum of frequencies reach a value. Currently I am doing this in PHP as .. ...
5
votes
2answers
107 views

Resolving DUPLICATE for a column with UNIQUE

I have a few column with UNIQUE INDEX. In some queries, duplicates should be acceptable, in which a postfix should be added to the value. For example, if test title exits, we change it to test ...
1
vote
2answers
123 views

Is it always bad to use SELECT * FROM?

It is widely recommended NOT to use SELECT *. I understand this, as it is not a good idea to bring the entire row into memory, when only a few cells are needed. Is it still bad to use SELECT * when ...
1
vote
2answers
394 views

How to insert into junction table using triggers

Sorry in advance if this is "basic SQL." I wanted to know how to update my junction tables automatically. For example, these are my tables. Artist and Song are base tables and SongArtist is the ...
2
votes
1answer
153 views

Recovering from a stuck query

I have a big DELETE query (deleting 20M rows from a 600M row table with condition according to indexed column) that is stuck - running already for 17hrs. Because it's an InnoDB table, killing it will ...
1
vote
1answer
119 views

Index strategy for a Queue Table, getting rid of filesort

I am trying to get rid of a filesort operation (and preferably also optimize a bottleneck query). We are using an innodb mysql table as a queue to process various incoming business activities. It is ...
1
vote
2answers
368 views

Deleting Entries from Table not reducing my DB file

Iam usind INNODB Engine with innodb_table_per_file , so every table has it's own .ibd file instead of ibdata1 file. When i Entered 512 Record in my users table its size get increased to 200kb from 96 ...
3
votes
2answers
979 views

Cannot write to mysql database while select query in process

Running Mysql 5.1.57 on InnoDB, and have a database locking issue. I have two separate sessions connected to a single database MySQL. On the first session, I run a long SELECT query (technically a ...
0
votes
1answer
115 views

How to interpret explain sql?

SELECT DISTINCT TB.ID, TB.Latitude, TB.Longitude, 111151.293413 * SQRT( pow( - 6.185 - TB.Latitude, 2 ) + pow( 106.773 - TB.Longitude, 2 ) * 0.988392289802 ) AS Distance FROM `tablebusiness` AS TB ...
1
vote
3answers
1k views

Is it normal to use many Triggers?

I have many so-called summary columns throughout my database to count number of rows in other tables. For example, counting the number of comments by a user (a column in the user table). Currently, I ...
4
votes
1answer
231 views

Does the order of columns has a significant effect on INSERT?

Do we experience a noticeable difference in performance for these two queries? INSERT INTO table (col1, col2, col3, col4, col5) ... and INSERT INTO table (col5, col3, col1, col2, col4) ... Do we ...
1
vote
1answer
1k views

How to use ON DUPLICATE KEY for UPDATE

Consider a table of CREATE TABLE test ( id int(11) unsigned NOT NULL AUTO_INCREMENT, external_id int(11), number smallint(5), value varchar(255), UNIQUE INDEX (external_id, number), PRIMARY KEY(id) ...
1
vote
2answers
3k views

How to use RESTRICT for Foreign Key in mysql?

In the database structure of CREATE TABLE Country ( name varchar(40) NOT NULL, PRIMARY KEY (name) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE City ( name varchar(40) NOT NULL, ...
1
vote
2answers
474 views

Usage of RESTRICT or No ACTION in FOREIGN KEY Constraints

Sorry if this question is naive, but I was unable to understand possible usage of RESTRICT or No ACTION. Consider a simple database of CREATE TABLE column1 ( first_id int(11) NOT NULL AUTO_INCREMENT, ...
1
vote
2answers
4k views

How to join two table and show one query result in MySQL?

I have a table1 (records 3), and table2 (records 3). Where i have field name in both. Now i want to make a result from those two table, which will show me both table records and take only one if there ...
5
votes
1answer
345 views

Dealing with temp tables when I have not control over db variables

I have no control over things like tmp_table_size and max_heap_table_size, and so as our tables grow the time taken by queries requiring temp tables is growing geometrically. I am wondering if there ...
7
votes
1answer
1k views

Unexplained InnoDB timeouts

I've been seeing some very basic updates timing out lately and have not been able to determine the cause. An example: //# Query_time: 51 Lock_time: 0 Rows_sent: 0 Rows_examined: 0 UPDATE photos ...