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() method, the second optional parameter that this method receives in the MongoDB query document is the list of fields to retrieve. In MongoDB, when you execute the Find () method, it displays all the fields of the document by default. To limit the fields that are displayed, you need to set the value for the field list to 1 or 0. 1 is used to display fields, and 0 for hidden fields.Grammar:>db. Collection_name.find ({},{key:1}) must have an empty curly brace {}, with multiple fields enclosed in

net Services ReferenceThe documentation explains several important files about listening, Tnsnames.ora, Listener.ora, Sqlnet.ora, etc.Backup and Recovery User ' s GuideDescribes the various uses of RmanApplication Development page PL/SQL Packages and Types ReferenceIncludes features of various Oracle self-built packages and functions, parameter descriptions. If you do not know the package, can be found here, such as Dbms_stats.PL/SQL Language Referen

: 　　　　Db.collectionName.update ({condition},{requires modified field and value},{upsert/multiple}) 　　The update () operation of MongoDB focuses on modifiers: 　1. $inc : specifically used to increase or decrease numbers, only for integers, long integers, and double-precision floating-point numbers, the value of $inc key must be a number, cannot be an array, string, or other non-numeric value, if the key does not exist, it is created 　　　　 $inc Add Direct Write number (reward:5), subtract (reward:-

Sys.dba_registry;comp_id comp_name VERSION STATUS-------------------- ---------------------------------------- ------------------------------ --------------------Catalog Oracle Database catalog views 10.2.0.5.0 VALIDCatproc Oracle Database Packages and Types 10.2.0.5.0 VALIDOWM Oracle Workspace Manager 10.2.0.5.0 VALIDJAVAVM jserver Java Virtual machine 10.2.0.5.0 VALIDXML Oracle XDK 10.2.0.5.0 VALIDCatjava Oracle Database Java Packages 10.2.0.5.0 VALIDEXF Oracle Expression Filter 10.2.0.5.0 VA

updated, you can use the atomic update modifier (updated modifier) to specify that some fields in the document should be modified. Suppose: To store analytic data for a Web site in a collection, the counter is incremented whenever someone accesses the page. You can use the updater to modify the atomicity to accomplish this increase. Each time someone accesses it, it finds the page through a URL and adds the value of "pageviews" with the "$inc" modifier >db.analytics.update ({url: "www.example.

Fourth Step: Configure environment variablesfirst create a new folder on this machine, C Directory is , configure environment variables for a folderNative My Computer (computer) à à - Environment Variables variable:= Note: This is the most important. Wrong will report variable: Note: This is to solve the database garbled problem Ld_library_path = c:\\\\oracleSQLPath = c:\\\\oraclePath ; C:\\\\oracleC:\\\\java\\\\jdk1.7.0_51\\\\bin; C:\\\\java\\\\jre7\\\\bin; C:\\\\windows\\\\system32; C:\\\\

type number . If char have data type char , then The length includes all trailing blanks. If char is null and then this function returns NULL. Restriction on LENGTHB The LENGTHB function was supported for Single-byte lobs only. It cannot is used with CLOB and NCLOB data in a multibyte character set.ExamplesThe following example uses the LENGTH function using a single-byte database character set:Select Length (' Candide ') "Length in characters" from DUAL; Length in characters--------------

1. IBM DB2 official documentation, Release Notes, Admin, Developer ' s GUID, etc., multi-lingualHttp://www-306.ibm.com/software/data/db2/udb/support/manualsNLVv8.html#cn_main2. This should also be from the official IBM website, but here to see, do not go to search again, EnglishDocument Libraryhttps://aurora.vcu.edu/db2help/db2c0/frame3.htm#db2c009Suggest friends, look at the Chinese document although happy dripping, quickly understand the technical p

Reference Link: https://dev.mysql.com/doc/refman/5.6/en/optimize-overview.htmlArticle Summary:Overview:The basic optimization starts from the software level rule, because the software affects the hardware, the high-level optimization starts from the internal mechanism such as CPU and IO. Ordinary users to retrofit software and hardware configuration to improve performance, advanced users to improve the performance of MySQL software.Basic design is most important for database performance. such as

://www.baidu.com as an example.2) Click the "Start Recording" button (the section marked in the red circle in the figure) to start recording.3) After you start recording, you can work directly in the Badboy embedded browser (on the right side of the main interface) and all operations are recorded in the edit window on the left side of the main interface (the section labeled in the picture).5) When the recording is complete, click the Stop Recording button in the toolbar (the part marked in the r

Environment Introduction:Vmware12+redhat linux7.5 x86_64+oracle 18CSystem InstallationCreate a virtual hostSystem partitionSelect a desktop environmentPerform the installation processDescription1, the system installation, grid installation directory space requirements greater than 100G (before the installation of 12c requirements)2, after the installation of a database server, directly with the full cloning of the way to replicate to another database server.Database installation mediaLinux. X64_

directoryChown-r mysql/application/mysql/ Change the directory owner/application/mysql/bin/mysql_install_db--basedir=/application/mysql--datadir=/application/mysql/data/--user= MySQL initialize database file/application/mysql/bin/mysqld_safe start MySQLEcho ' Exportpath=/application/mysql/bin: $PATH ' >>/etc/profileSource/etc/profile Configuring environment variablesCp/home/tool/mysql-5.1.70/support-files/mysql.server/etc/init.d/mysqld Copy boot filechmod 755/etc/init.d/mysqld giving execute p

Binary package:https://www.mongodb.org/dl/linuxTar XF mongodb-linux-x86_64-3.0.5.tgz-c/usr/local/Mv/usr/local/mongodb-linux-x86_64-3.0.5/usr/local/mongodbMkdir/usr/local/mongodb/dataTouch/usr/local/mongodb/logsGroupadd MongoDBUseradd-g MongoDB mongodb-s/sbin/nologin-mChown-r Mongodb:mongodb/usr/local/mongodbLl/usr/local/mongodb/binVim/etc/profileMongod--dbpath=/usr/local/mongodb/data--fork--logpath=/usr/local/mongodb/logs[Email protected] soft]# MONGOMongoDB Shell version:3.0.5Connecting To:test

": "MongoDB"}{"_id": 104, "name": "Liang", "title": "MongoDB"}Save () methodThe Save () method replaces an existing document with an incoming document. The syntax format is as follows:Db.collection.save ({Writeconcern: })Db.mycol3.insert ({"_id": +, "name": "Liang", "title": "MongoDB"})Db.mycol3.save ({"_id": +, "name": "Liang2", "title": "MongoDB2"})Db.mycol3.find (){"_id": +, "name": "Liang2", "title": "MongoDB2"}more examplesUpdate only the first record:Db.col.update ({"Count": {$gt: 1}}, {$s

/mysql5.6/dataSkip-external-lockingKey_buffer_size = 32MMax_allowed_packet = 50MTable_open_cache = 1024Sort_buffer_size = 4MNet_buffer_length = 8KRead_buffer_size = 4MRead_rnd_buffer_size = 512KMyisam_sort_buffer_size = 64MThread_cache_size = 128#query_cache_size = 128MTmp_table_size = 64Mmax_join_size=3g#skip-networkingSkip-name-resolveMax_connections = 500max_connect_errors = 1000Open_files_limit = 65535#log-bin=mysql-bin#binlog_format =rowServer-id = 1#expire_logs_days = 1#default_storage_eng

12.2.0.1.0-production Start Date 24- MAY-2018 00:36:52 Uptime 0 days 0 hr. The min. SEC Trace level off Security on:local OS authentication SNMP OFF Listener Parameter file/home/app/oracle/product/12.2.0.1/db_1/network/admin/listener.ora Listener Log File/home/app/oracle/diag/tnslsnr/hcdb/listener/alert/log.xml Listening Endpoints Summary ... (description= (address= (protocol=tcp) (HOST=HCDB) (port=1521)) (description= (address= (PROTOCOL=IPC) (KEY= EXTPROC1521))) Services Summary ..

Tags:. exe info base class MIL configuration share Run databaseOracle 10G Installation Guide 1, unzip the file 10201_database_win32.zip, and double-click the Setup.exe directory, the installation interface appears as follows: 2, Enter the password and confirm the password, such as:password, click Next, the following progress bar appears, Note: This password is the administrator password. 3, check the prerequisites, select the Red box as shown in the selection box, such as: 4, click "

...Copying oraenv To/usr/local/bin ...Copying coraenv To/usr/local/bin ...Creating/etc/oratab file ...Entries'll be added to The/etc/oratab file as needed byDatabase Configuration Assistant When a database is createdFinished running generic part of root.sh script.Now product-specific root actions would be performed.[Email protected] ~]#The database is in a startup state after installation endsIn the command behavior Scott user unlocks:Sql>conn/as SYSDBA Switch to system administratorSql>alter u

Service (monitoring service) for restart operation8. Configure the TestStart with attachment, command prompt, enter command: tnsping instance name, for example: this example-tnsping dg4msql9. Create DblinkTo create a dblink condition:1. Look at having dblink processing authority;Log in to the SYS user to view2. Give creation permission, under normal circumstances give droppublic DATABASE link, create publicdatabase link can be;Grant DROP public databaselink,create publicly DATABASE LINK to Scot

, change Login:Tested successfully,As with Oarcle, right-click Compatibility opens without repeating:Select the installation path, Next:The general meaning of the error is: The installation path can not have spaces and special characters, modified:Next, no error:All users, Next:Click Next and the installation is complete.Test log on to Oracle with PL/sql:Error (blank window): This is generally due to insufficient permissions to close the open window of PL/SQL. Right-click PL/SQL Desktop shortcut