【MongoDB】The connection between two tables,mongodbtablesIn mongoDB, there are two general way to connect with two tables. Manual Connection and use DBRef1. Basically manual connection Firstly init the data which was saved in the different
MongoDB 操作手冊CRUD查詢指標,mongodbcrud枚舉遍曆指標概述前面已經講過,db.collection.find()如果沒有指定給一個var聲明的變數,將自動枚舉前20條記錄。手動枚舉指標在mongo控制台中,將查詢賦給一個var聲明的變數,讓其不自動枚舉。var cur = db.testData.find();然後每次調用這個指標,將自動遍曆20條cur;也可以使用指標的next()方法來擷取下一條記錄var cur =
【MongoDB】The basic operation of Index in MongoDB,mongodboperationIn the past four blogs, we attached importance to the index, including description and comparison with usage of index. Now in this blog, we will mainly focus on the basic operation of
Select * 一定不走索引是否正確?,select走索引走索引指的是:SQL語句的執行計畫用到了1、叢集索引尋找 2、索引尋找 ,並且查詢語句中需要有where子句根據where子句的過濾條件,去叢集索引或非叢集索引那裡尋找記錄一張表只有一列的情況:叢集索引 USE [tempdb] GO CREATE TABLE t1 ( id INT ) GO CREATE CLUSTERED INDEX CIX_T1 ON [dbo].[t1](ID ASC)
GoldenGate Lag For Huge Insert,goldengatelag前些天客戶的ogg延遲到達8小時左右,於是我當時用logdump追蹤了一下:看進程狀態:send extsa stausEXTRACT ZBDBA (PID 2269368) Current status: Recovery complete: Processing data with empty data queue Current read positions: Redo thread #: 1
set RowCount 與 top n,setrowcounttop有的時候,使用top n中的n是一個變數,那就需要用()來完成:declare @count1 intset @count1 = 8select top <strong>(@count1)</strong> * from MyTable如果用set RowCount一樣可以達到相同的效果declare @count1 intset @count1 = 8 set RowCount
【MonogDB】The description of index(二) Embedded and document Index,monogdbembeddedIn this blog, we will talk about another the index which was called "The embedded ". First we init 1w the records as follows:2.2 The embedded
建立MySQL從庫,建立MySQL我們知道Oracle有DataGuard即時備份資料,可以做主備切換,而MySQL也有自己的一套備庫方案,稱之為主從複製。搭建MySQL從庫是為了即時同步主庫資料,同時也可以分擔主庫的讀壓力,對資料庫端做成讀寫分離結構。搭建MySQL主從庫注意點:1.主庫和從庫的 server-id 一定不能相同。2.在主庫建立replication slave賬戶。grant replication slave on *.* to 'repl'@'192.168.0.232'