標籤:1.對查詢進行最佳化,應盡量避免全表掃描,首先應考慮在 where 及 order by 涉及的列上建立索引。2.應盡量避免在 where 子句中對欄位進行 null 值判斷,否則將導致引擎放棄使用索引而進行全表掃描,如:select id from t where num is null可以在num上設定預設值0,確保表中num列沒有null值,然後這樣查詢:select id from t where num=03.應盡量避免在 where
標籤:資料庫 hang問題的診斷資訊收集方法來源於:How to Collect Diagnostics for Database Hanging Issues (文檔 ID 452358.1)適用於:Oracle Database - Enterprise Edition - Version 9.0.1.0 and laterOracle Database - Personal Edition - Version 9.0.1.0 and laterOracle Database -
標籤:如題,實現此功能的方法有很多,如果使用的是MVVM的開發模式,該如何?此功能? 很簡單,為TextBox建立一個附加屬性,就可以完美的解決此問題。建立一個附件屬性 IsOnlyAcceptFigure ,並為其添加屬性回呼函數即可。代碼如下:namespace WPF.Validation{ public class TextBoxOnlyAcceptFigureBehavior { public static readonly
標籤:Hello,i would have 2 unigui app. the first app is a simple authentification app and second will be the main app. I‘d like to have the following scenario.user "paul" arrive on the auth apppaul set his login and password.the auth app
標籤:Kernel Buildinghttps://www.raspberrypi.org/documentation/linux/kernel/building.md There are two main methods for building the kernel. You can build locally on a Raspberry Pi which will take a long time; or you can cross-compile, which
標籤:DFS代碼#include<iostream>#include<cstdio>using namespace std;#define Min(a,b) (a<b)?a:bconst int MAX_N=205;const int INF=0x30303030;int floors[MAX_N];int N, A, B;int step[MAX_N];int dfs(int k){ if(k<1||k>N) return INF;