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為什么說"B+樹索引適用于全鍵值,鍵值范圍或者最左鍵前綴查找"? 看高性能 Mysql 的困惑

還以書上例子來說 {代碼...} 這個(gè) B+tree 的索引示意圖能明白,但是為什么馬上在下文就說"B+樹索引適用于全鍵值,鍵值范圍或者最左鍵前綴查找" 我應(yīng)該如何去理解,是否和 B+tree 有著不...

From [MySQLdiscussion group] 2017-04-17 12:58:12 0  2  1085

How to undo an executed mysql UPDATE command

I was trying to make an update to my MySQL server and accidentally forgot to add an extra WHERE clause that wa...

From [MySQLdiscussion group] 2023-08-22 17:36:22 0  2  1083

Please God, please look at this question

What's going on? Every time I use the IN statement incorrectly, I select the state as "CA" or "...

From [MySQLdiscussion group] 2021-09-16 08:25:49 0  3  1083

javascript - axios upload data to php returns empty

1.vue 2.0 uses axios to upload data and returns empty, and the background is php 2.vue code {code...} 3.php co...

From [MySQLdiscussion group] 2017-06-20 10:05:38 0  2  1083

把sql語句查詢到的結(jié)果暫時(shí)保存

搜索關(guān)鍵字，并把搜索到的結(jié)果分頁 ， 怎么做不會(huì)出現(xiàn)問題 ？我用的sql語句是這樣的，$sql = "SELECT FROM ( SELECT FROM {$my_mysql_dbname}...

From [MySQLdiscussion group] 2017-02-03 17:03:51 0  1  1081

How to batch update mysql according to respective conditions

There are two existing tables. A is the detailed table id uid cost 0 1 4 3 Now we need to group the data with ...

From [MySQLdiscussion group] 2017-06-26 10:49:25 0  1  1079

php - Ask me about mysql transactions, locks and transactions?

For example, if the account balance is 100 yuan, and if the balance is greater than the transaction amount dur...

From [MySQLdiscussion group] 2017-06-24 09:41:23 0  1  1079

分頁顯示 - MySQL分頁查詢，是用LIMIT m,n，還是先查出所有ID再在前端分頁？

用傳統(tǒng)的LIMIT m, n做分頁查詢需要這么幾步： 用SELECT COUNT(*) FROM table WHERE condition ORDER BY ...查到總數(shù)并算出有多少頁； 用SELECT column...

From [MySQLdiscussion group] 2017-04-17 16:38:37 0  6  1079

mysql - If PHP does not use PDO, how to prevent injection when constructing SQL statements?

If PHP does not use PDO, how to prevent injection when constructing SQL statements? Can sprint format string b...

From [MySQLdiscussion group] 2017-06-22 11:54:34 0  1  1078

Which label should be used in mybatis to use mysql's ON DUPLICATE KEY UPDATE syntax to implement existence and update?

Mybatis seems to only provide four tags for add, delete, modify and check (<insert>/<upda...

From [MySQLdiscussion group] 2017-06-10 09:49:42 0  1  1078

mysql - 詳細(xì)論述聯(lián)表查詢與分步查詢的優(yōu)缺點(diǎn)

本人在開發(fā)中喜歡用聯(lián)表查詢，因?yàn)檫@樣可以大大簡化代碼。 使用分步查詢不僅需要編寫多條sql語句，而且需要通過代碼去實(shí)現(xiàn)哈希關(guān)系，需要使用到多個(gè)for循環(huán)。維護(hù)時(shí)，對代碼的理解比較困難。 以下是本人對這些優(yōu)...

From [MySQLdiscussion group] 2017-04-17 16:37:06 0  1  1078

mysql表無法添加字段是什么問題啊

添加過一次sql失敗了之后，再執(zhí)行該sql，就報(bào)錯(cuò)了，無法添加字段 sql： ALTER TABLE bms_c.room ADD COLUMN live_id INT(11) DEFAULT '0' 錯(cuò)誤信息： Que...

From [MySQLdiscussion group] 2017-04-17 11:47:54 0  2  1076

linux - 編譯安裝的mysql，后來apt-get install libmysqlclient-dev。然后再刪除掉。mysql起不來了。

編譯安裝的mysql。 base dir: /usr/local/mysql data dir: /data/mysqldata 今天安裝sphinx，說需要libmysqlclient，遂： {代碼...} 后邊不想裝...

From [MySQLdiscussion group] 2017-04-17 11:17:09 0  0  1074

在數(shù)據(jù)庫中保存時(shí)間, 能不能直接用數(shù)字的時(shí)間戳存到bigint中?這樣做有什么明顯弊病?

像這樣 1476355731 的數(shù)字

From [MySQLdiscussion group] 2016-11-09 13:31:20 0  4  1073

mysql-配置 - Mysql創(chuàng)建數(shù)據(jù)庫時(shí)提示Error 1044

使用非root用戶登錄時(shí)創(chuàng)建數(shù)據(jù)庫會(huì)提示Error1044，使用root用戶登錄則能創(chuàng)建數(shù)據(jù)庫。百度了一下似乎是權(quán)限問題，我該如何操作將我所登錄的用戶能創(chuàng)建數(shù)據(jù)庫？ Mysql版本: 5.7.10 MySQL Commu...

From [MySQLdiscussion group] 2017-04-17 15:27:34 0  2  1071