… be held at Portland State University’s Smith Memorial Student Union, located at 1825 SW Broadway, Suite 327/8/9 Portland…
Post: Percona MySQL University @Portland: June 17
May 22, 2013 By 1 Comment
… be held at Portland State University’s Smith Memorial Student Union. We’ll finalize the schedule next week and still have…
Post: UNION vs UNION ALL Performance
October 5, 2007 By 15 Comments
… inside of union clause being cool thing. But So is UNION ALL indeed faster than UNION DISTINCT (the UNION is shortcut for UNION DISTINCT) ? Indeed… than UNION as it indeed should be. So why UNION ALL is faster than UNION DISTINCT ? The first informed guess would be – because UNION… store result set, however this is not correct – both UNION ALL and UNION distinct use temporary table for result generation. Perhaps one…
Post: SELECT UNION Results INTO OUTFILE
September 14, 2011 By Leave a Comment
… | hire_date | hire_date | 3 | NULL | 179 | Using where | | NULL | UNION RESULT | | ALL | NULL | NULL | NULL | NULL | NULL | | +—-+————–+————–+——-+—————+———–+———+——+——+————-+ 5 rows in set (0.00 sec) Compared to using UNION simply: mysql [localhost] {msandbox} (employees) > EXPLAIN SELECT * -> FROM employees -> WHERE…
Post: Possible optimization for sort_merge and UNION ORDER BY LIMIT
September 18, 2007 By 10 Comments
…: const rows: 54268 Extra: *************************** 3. row *************************** id: NULL select_type: UNION RESULT table: type: ALL possible_keys: NULL key: NULL key…: 54268 Extra: Using where *************************** 3. row *************************** id: NULL select_type: UNION RESULT table: type: ALL possible_keys: NULL key: NULL key…
Post: MySQL: Followup on UNION for query optimization, Query profiling
August 14, 2006 By 14 Comments
… | people | ref | age | age | 1 | const | 12543 | Using where | | 2 | UNION | people | ref | age | age | 1 | const | 12741 | Using where | | 3 | UNION | people | ref | age | age | 1 | const | 12631 | Using where | |NULL | UNION RESULT | | ALL | NULL | NULL | NULL…
Post: Using UNION to implement loose index scan in MySQL
August 10, 2006 By 15 Comments
… people WHERE age=18 AND zip IN (12345,12346, 12347) -> UNION ALL -> SELECT name FROM people WHERE age=19 AND zip IN (12345,12346, 12347) -> UNION ALL -> SELECT name FROM people WHERE age=20 AND zip IN (12345,12346, 12347) -> UNION ALL -> SELECT name FROM people WHERE age=21 AND zip…
Comment: UNION vs UNION ALL Performance
May 2, 2012 By 15 Comments
… tab_a union all select distinct b col from tab_b union all select distinct c col from tab_c union all select… from tab_a union all select b col from tab_b union all select c col from tab_c union all select d… from tab_a union select distinct b col from tab_b union select distinct c col from tab_c union select distinct d…
Post: MySQL 5.5 and MySQL 5.6 default variable values differences
February 21, 2013 By 8 Comments
…/ | | OPTIMIZER_SWITCH | index_merge=on,index_merge_union=on,inde | index_merge=on,index_merge_union=on,inde | +—————————————————+——————————————+——————————————+ 56 rows in set…_SWITCH VARIABLE_VALUE: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown…_SWITCH VARIABLE_VALUE: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown…
Comment: Percona build7 with latest patches
November 16, 2008 By 26 Comments
… struct/union member: io_reads “os0file.c”, line 1954: undefined struct/union member: io_read “os0file.c”, line 1975: undefined struct/union member: io_reads_wait_timer “os0file.c”, line 3523: undefined struct/union member: io_reads “os0file.c”, line 3524: undefined struct/union…
