… KEY (`id`)) —————————————————————————————————— $mysql=mysql_connect(’127.0.0.1′,’root’,”); mysql_select_db(‘test’,$mysql); function display_menu($parent, $level) { $result = mysql_query(“SELECT a.id, a.label, a.link, Deriv1.Count FROM `menu` a LEFT OUTER JOIN…
Post: Eventual Consistency in MySQL
November 18, 2011 By 8 Comments
… orphaned rows in Bar: SELECT Bar.ID FROM Bar LEFT OUTER JOIN Foo ON (Bar.X,Bar.Y) = (Foo.A,Foo.B….TABLE_SCHEMA, ‘.’, K.TABLE_NAME, ‘ AS ‘, K.CONSTRAINT_NAME, ‘ ‘, ‘LEFT OUTER JOIN ‘, K.REFERENCED_TABLE_SCHEMA, ‘.’, K.REFERENCED_TABLE_NAME, ‘ AS ‘, K… AN ORPHAN mysql> SELECT Bar_ibfk_1.ID AS `test.Bar.ID` FROM test.Bar AS Bar_ibfk_1 LEFT OUTER JOIN test…
Post: Avoiding auto-increment holes on InnoDB with INSERT IGNORE
November 29, 2011 By 8 Comments
… and assigns the new value to the column. Prior to MySQL 5.1.22 InnoDB used a method to access that… a value using a LEFT OUTER JOIN: insert into foo(name) select 1 from mutex left outer join foo on foo.name=1 where… IGNORE: insert into foo(name) select 1 from mutex left outer join foo on foo.name=1 where mutex.i = 1 and…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
… features available to SELECT statements. Refresh type Aggregation Outer join All SQL functions Built using SQL Requires FlexCDC… | 155187034 | <-- too high +------------------+ 1 row in set (0.68 sec) mysql> select sum(total_lines) from dashboard_customer_sales ; +——————+ |…
Post: MySQL Limitations Part 3: Subqueries
October 25, 2010 By 21 Comments
… the third in a series on what’s seriously limiting MySQL in certain circumstances (links: part 1, 2). This post is… table b. This is because MySQL rewrites the query to make the inner query dependent on the outer query, which could be… past and have fixed it. And many MySQL users have learned to simply write JOINs instead, so it isn’t that much…
Post: Using Flexviews - part one, introduction to materialized views
March 23, 2011 By 3 Comments
… conceptually so too is the output of a SQL statement. MySQL even includes a SQL statement that makes this perfectly clear… space (similar to ALTER TABLE) Supports all SQL syntax (like outer join) but can’t be refreshed to a specific point in… work. And some drawbacks: Not all SQL syntax supported (no outer join), no non-deterministic functions, etc. There is overhead for change…
Comment: Multi-Column IN clause - Unexpected MySQL Issue
October 18, 2008 By 21 Comments
… I found out that when we use IN clause, MySQL first executes the outer query i.e. the PRIMARY query as shown… executes the inner subquery. To bypass this problem I used JOIN and the execution time reduced drastically from few seconds to… outer join 106pages.106pages as t2 on t1.url = t2.url WHERE t2.url_crc IN ((2752937066,3799762538); I have used self join…
Post: EXPLAIN EXTENDED can tell you all kinds of interesting things
June 15, 2010 By 7 Comments
… OUTER JOIN, then MySQL can immediately return an empty set because it infers that there is no way that rows could be returned. MySQL… used the comma syntax, but when MySQL rewrote the query it switched it to use the JOIN keyword. This should put to… join and ANSI JOIN syntax. They are intrinsically the same. Last, EXPLAIN EXTENDED can show you information about the query rewrites that MySQL…
Post: MySQL VIEW as performance troublemaker
August 12, 2007 By 57 Comments
… creation from the outer query and plus if you use more then one Temporary Tables views which you join together you may… solve the same problem having things more modular and using MySQL VIEWs ? mysql> create view user_counts as select user_id,count… a very artificial query which will JOIN 2 views just to see how indexes are used: mysql> explain select uc.cnt+uc2…
Comment: Why MySQL could be slow with large tables ?
July 6, 2007 By 141 Comments
… sqlite DB and do the joins there, thereby minimising load on the main server or even the mysql server. (running on 5… PC) (select a, join b, where c…) eg: select a.a, b.x, etc.. from (select … .. ) a left outer join (select … ) b on b.a = a.a etc.. (in total I have like close to 11 subqueries joining a min…
