当表有数千条记录时，Sql TOP 1查询执行速度很慢？
select Top 1 * from AA011 WHERE order By datadate DESC
答案 0 :(得分：2)
查看查询的执行计划。
您很可能会看到类似表/聚簇索引扫描然后排序的内容。这意味着您没有在表的datadate字段上构建索引 - 因此SQL服务器必须从表中检索所有数据并对其进行排序以获得前1个值。
如果要在此列上构建索引，SQL Server将使用此索引而不是检索所有数据并对其进行排序 - 因此它将大大提高性能。
答案 1 :(得分：1)
在"use strict";
var path = require('path');
var webpack = require('webpack');
var bower_dir = path.join(__dirname, '/bower_components');
var HtmlWebpackPlugin = require('html-webpack-plugin');
var config = {
addVendor: function(name, path){
this.resolve.alias[name] = path;
this.module.noParse.push(path);
},
entry: {
app: ["./app/js/index.js"],
vendors: ["d3", "_"]
},
output: {
"path": process.env.NODE_ENV === 'production' ? './dist' : './build',
"filename": "bundle.js"
},
module: {
noParse: [],
loaders: [
{ test: /\.css$/, loader: "style-loader!css-loader?root=." },
{ test: /\.js?$/, exclude: /(node_modules|bower_components)/, loader: 'babel' },
{ test: /\.gif$/, loader: "url-loader?mimetype=image/png" },
// { test: /bootstrap\/js\//, loader: 'imports?jQuery=jquery' },
{ test: /.(png|woff(2)?|eot|ttf|svg)(\?[a-z0-9=\.]+)?$/, loader: 'url-loader?limit=100000' }
]
},
resolve: {
alias: {},
root: [path.join(__dirname, "app/css"), path.join(__dirname, "app/js")]
},
plugins: [
// This plugin makes a module available as variable in every module
new webpack.ProvidePlugin({
d3: "d3",
"_": "_"
}),
// CommonsChunkPlugin will take the vendors chunk and create a commonly used js file
new webpack.optimize.CommonsChunkPlugin('vendors','vendors.js', Infinity),
// https://www.npmjs.com/package/html-webpack-plugin
new HtmlWebpackPlugin({
title: 'D3 and react',
template: 'build/index.html'
})
]
};
config.addVendor('d3', bower_dir + '/d3/d3.min.js');
config.addVendor('_', bower_dir + '/lodash/lodash.min.js');
module.exports = config;
列上创建clustered index，以加快流程
datadate