MySQL explain ref: NULL
mysql> EXPLAIN SELECT id,title,production_year FROM title. -> WHERE title ... possible_keys: title key: title key_len: 152 ref: NULL rows: 176 filtered: 100.00. ,2009年6月23日 — In the EXPLAIN below, is ref: NULL a bad thing? mysql explain SELECT * FROM mytable WHERE item_id='09N1320347' AND value_id IN (2,3 ... ,The value can be NULL if the row refers to the union result of other rows. ... The ref column shows which columns or constants are compared to the index named ... ,2017年1月16日 — MySQL 提供了一个EXPLAIN 命令, 它可以对SELECT 语句进行分析, ... key_len: 8 ref: const rows: 1 filtered: 100.00 Extra: NULL 1 row in set, ... ,Mysql之sql語句優化：explain. 其他 · 發表 2019-02-09. explain的列分析 ... ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 31 Extra: Using ... ,2019年1月3日 — F：ref_or_null：與ref方法類似，只是增加了null值的比較。實際用的不多。 例如： SELECT * FROM ref_table. WHERE key_column=expr OR ... ,This causes my query to use a temporary table and a filesort later (when I've added more joins)... 14:45:21 (60) > EXPLAIN select * from users u inner join ... ,key: null key_len: NULL ref: NULL rows: 583. Extra: Using where. select_type: 表示SELECT ... 2. type = index，索引全掃描，MySQL遍歷整個索引來查詢匹配的行. ,直接來看在MySQL關於索引的一個重要指令: EXPLAIN ... type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 5 Extra: Using where 1 row in ... ,MySQL那些事兒系列第18 篇 ... EXPLAIN SELECT * FROM AVGals WHERE name = '初音みのり'-G *************************** 1. row ... id: 1 select_type: SIMPLE table: AVGals type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL ...
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 MySQL explain ref: NULL 相關參考資料
Indexes - Percona
mysql> EXPLAIN SELECT id,title,production_year FROM title. -> WHERE title ... possible_keys: title key: title key_len: 152 ref: NULL rows: 176 filtered: 100.00. https://www.percona.com Is ref: NULL bad?: mysql — LiveJournal
2009年6月23日 — In the EXPLAIN below, is ref: NULL a bad thing? mysql explain SELECT * FROM mytable WHERE item_id='09N1320347' AND value_id IN (2,3 ... https://mysql.livejournal.com MySQL 8.0 Reference Manual :: 8.8.2 EXPLAIN ... - MySQL
The value can be NULL if the row refers to the union result of other rows. ... The ref column shows which columns or constants are compared to the index named ... https://dev.mysql.com MySQL 性能优化神器Explain 使用分析_后台开发 ...
2017年1月16日 — MySQL 提供了一个EXPLAIN 命令, 它可以对SELECT 语句进行分析, ... key_len: 8 ref: const rows: 1 filtered: 100.00 Extra: NULL 1 row in set, ... https://segmentfault.com Mysql之sql語句優化：explain - IT閱讀 - ITREAD01.COM
Mysql之sql語句優化：explain. 其他 · 發表 2019-02-09. explain的列分析 ... ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 31 Extra: Using ... https://www.itread01.com MySQL優化之Explain命令解讀，optimizer_trace - IT閱讀
2019年1月3日 — F：ref_or_null：與ref方法類似，只是增加了null值的比較。實際用的不多。 例如： SELECT * FROM ref_table. WHERE key_column=expr OR ... https://www.itread01.com Trying to reduce mysql query, why is 'ref' NULL? - Stack ...
This causes my query to use a temporary table and a filesort later (when I've added more joins)... 14:45:21 (60) > EXPLAIN select * from users u inner join ... https://stackoverflow.com 透過Explain分析效能 - Medium
key: null key_len: NULL ref: NULL rows: 583. Extra: Using where. select_type: 表示SELECT ... 2. type = index，索引全掃描，MySQL遍歷整個索引來查詢匹配的行. https://medium.com 關於索引的一些探討(一) - iT 邦幫忙 - iThome
直接來看在MySQL關於索引的一個重要指令: EXPLAIN ... type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 5 Extra: Using where 1 row in ... https://ithelp.ithome.com.tw 關於索引的一些探討(四) - iT 邦幫忙 - iThome
MySQL那些事兒系列第18 篇 ... EXPLAIN SELECT * FROM AVGals WHERE name = '初音みのり'-G *************************** 1. row ... id: 1 select_type: SIMPLE table: AVGals type: ALL possible_keys: NULL key: NULL ... https://ithelp.ithome.com.tw |