nosql database comparison

Simple string comparison results are imprecise.select*from表明wheretimes>‘2088/12/8 10:02:40‘(x)The conversion function is as follows (the database is varchar):select*fromh_hotelcontextwherenow()betweenSTR_TO_DATE(Start_time,‘%Y-%m-%d %H:%i:%s‘)andSTR_TO_DATE(End_time,‘%Y-%m-%d %H:%i:%s‘);selectmax(addtime)fromstudentwhere stuid=‘9‘;(×)selectmax(STR_TO_DATE(addtime,‘%Y/%m/%d %H:%i:%s‘))fromstudent wherestuid=

Tags: text many speed minimum style and Ext Max classDbcpDBCP may be the most used open source connection pool, probably because of the ease of configuration, and many examples of open source and Tomcat applications are used for this connection pool.This connection pool can set the maximum and minimum connections, connection waiting time, etc., basic functions are available. The configuration of this connection pool is described in the attachment compression package: Dbcp.xml.Usage Evaluation: I

SqlBulkCopy Insert, Time 244ms. 1DataTable datatable =NewDataTable ();2DATATABLE.COLUMNS.ADD ("ID",typeof(int)); 3DATATABLE.COLUMNS.ADD ("Dataid",typeof(string)); 4DATATABLE.COLUMNS.ADD ("isenable",typeof(BOOL)); 5 for(inti = -; I +; i++) 6 { 7DataRow datarow =Datatable.newrow ();8datarow["ID"] =i;9datarow["Dataid"] ="00000000000502"; Tendatarow["isenable"] =true; One DataTable.Rows.Add (dataRow); A } -Stopwatch Stopwatch =NewStopwatch (); - Stopwatch.sta

Label:Exists: Usage: SELECT * FROM table1 where exists (SELECT * from table2 where table1.id = table2.id)Returns records with the same ID in Table1 and table2 (double loop) result and in syntax, thinking differently,In:select * FROM table1 where ID in (select ID from table2)2 ideas are different: exists: first get each table1 data, and then get the ID field, go to table2 table to find the corresponding value, find the description matches the conditionIn: The ID probability is obtained first, and

Label:MongoDB Grammar MySQL syntax Db.test.find ({' name ': ' Foobar '}) Db.test.find () Db.test.find ({' ID ': ten}). Count () Db.test.find (). Skip () Limit Db.test.find ({' ID ': {$in: [25,35,45]}} Db.test.find (). Sort ({' ID ': -1}) Db.test.distinct (' name ', {' ID ': {$lt:}}) Db.test.group ({key:{' name ': ' true},cond:{' name ': ' foo '},reduce:function (obj,prev) {prev.msum+=obj.marks;},initial: {msum:0}}) Db.test.find (' this.id Db.test.insert ({' name ': ' Foobar ', ' age '

Tags: loading HBA datasets Organization development int checked Storage sub Data Warehouse is a subject-oriented (Subject oriented), integrated (integrate), relatively stable (non-volatile), data collection that reflects historical changes (time Variant). Used to support management decisions. (1) Topic-oriented: Index data in the warehouse is organized according to a certain subject domain. (2) Integration: Refers to the original distributed database

record occupied spaceTruncate [TABLE] table_name [reuse storage];For example: Delete all data from the users table and save space: Truncate table users reuse storage;Comparison of two DELETE statementsSince the DELETE statement deletes the record, the record is deleted one at a time, and the TRUNCATE statement does not produce fallback information when it deletes the data, so if you need to delete large amounts of data, using delete consumes more sys

Tags: http java using OS IO data ar CTIThe purpose of this test is to verify the performance of the current common database connection pool.TestCase Connection conn = dataSource.getConnection(); PreparedStatement stmt = conn.preparedStatement("select 1"); ResultSet rs = stmt.executeQuery(); while (rs.next()) { } rs.close(); stmt.close(); conn.close(); Test Codehttps://github.com/alibaba/druid/blob/master/src/test/java/com/alibaba/drui

table by the dependent constraint (constrain), trigger (trigger), index (index) "Delete table data and delete table structure";Stored procedures/functions that depend on the table are preserved, but become invalid states.The drop statement frees all the space occupied by the table.The speed at which data is deleted, in general: drop> truncate > DeleteUse occasions:When you no longer need the table, use drop;When you still want to keep the table, but to delete all records, use truncate;When you

features, including acid transaction support. If you need to perform a large number of insert or update operations in your app, you should use InnoDB, which can improve the performance of multiple user concurrency operations. Common commands:(1) View the storage type of table (three kinds): Show CREATE TABLE TableName Show table status from DBName where Name=tablename Mysqlshow-u user-p password--status dbname tablename (2) Modify the table's storage engine:

Front: PHP background to receive and query: Public Function Malllist () {//write method $goods =m (' shop_goods_info ');//instantiate database corresponding table $codes =i (' Param.bianhao '); Gets the foreground text box data if (Isset ($codes) $codes!= ') { $where [' Code ']= $codes; $this->assign (' codes ', $codes); Display } $info = $classify->where (Array (' Code ' => $code))->find ();//query syntax 2. Or: With $_ge

Data | database | data type///Comparison of data types in the database with C # private string Changetocsharptype (String type) { String reval=string. Empty; Switch (type. ToLower ()) { Case "int": Reval= "Int32"; Break Case "Text": Reval= "String"; Break Case "bigint": Reval= "Int64"; Break Case "binary": Reval= "system.byte[]"; Break Case "bit": Reval= "Boolean

contain only the index of the field, but in the MyISAM table, you can establish a federated index with other fields better and faster auto_increment processing If you specify a auto_increment column for a table, the InnoDB table handle in the data dictionary contains a counter called the autogrow counter, which is used to assign a new value to the column. The autogrow counters are stored only in main memory, not on disk algorithmic implementations of the calculator, see

By latitude, the database is compared stringbuffer SB = new StringBuffer () sb.append ("Select TimeKey,") Sb.append ("ROUND (6378.138*2*asin ( SQRT (POW (Sin (*pi ()/180-lat*pi ()/180)/2), 2), Sb.append (+cos (? *pi ()/180) *cos (Lat*pi ()/180) *pow (Sin ((? *pi ()/) ); Sb.append ("180-lng*pi ()/180)/2), 2)) *1000) as JL") Sb.append ("From T_news have JL Mysql takes a distance comparison between the specifi

(".$tableNot exist\n "); Continue; } for($i= 0;$iCount($structures 2);$i++){ if(1==1 !)In_array($structures 2[$i],$structures 1)) Echo $table.".".$structures 2[$i]." \ n "; }}//DB2 Compare DB1Echo("***** ". DATABASE2. "*****\n");foreach($db 1 as $table=$structures 1){ $structures 2=$db 2[$table]; if(Empty($structures 2)) { Echo(DATABASE2. ").$tableNot exist\n "); Continue; } for($i= 0;$iCount($structures 1);$i++){ if(1==0 !)In_array($structures 1[$i],$

Tags: ar data sp div c ad R EF BS Oracle Mysql Mssql Returns the start character in a string (from left) INSTR INSTR CHARINDEX Sub-string SUBSTR SUBSTRING SUBSTRING String length LENGTH LENGTH Len Returns the leftmost character of Len starting with the string str Left Left Returns the right-most Len character starting from the string str