SQL Server

Table Scan, index Scan, index lookup three differencesWe often hear this three noun in our daily work, what does it mean? Under what circumstances will the above situation occur? And how can we optimize our SQL execution more efficiently when it

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　String functions Name of function Describe Example CHARINDEX Finds the starting position of a specified string in another string SELECT CHARINDEX (' Jbns ', ' My Jbns

Declaring local variablesDECLARE @ variable name data typeDECLARE @name varchar (8)DECLARE @seat intAssign valueSET @ Variable name = value orSELECT @ variable name = valueSET @name = ' Zhang San 'SELECT @name = studentname from Student WHERE

In the process of using the database, we often need to calculate some of the data first, and then query it out, so we need to create a function to accomplish this task.The function you create typically has two return types, one that returns a

1 --CREATE table users--Creating user tables2 --(3 --IDs int primary key identity (.),4 --name nvarchar,--names5 --class nvarchar (200)--Class number6 --)7 8 --CREATE table class--Creating a class table9 --(Ten --classcode nvarchar ($) primary key,--

INNER JOIN: (INNER join)Inner joins use comparison operators to match rows in two tables based on values in the universal columns of each table(1) SELECT ... From table 1INNER JOIN table 2ON ...SELECT S.sname,c.courseid,c.scoreFrom score as CINNER

CREATE Table Table Name(Column Name 1 characteristics of the data type column,Column Name 2 characteristics of the data type column,...)Note: Boolean True and FALSE can be converted to the following bit value: True converts to 1,false to 0Source:Use

Elect Collationproperty (' Chinese_prc_stroke_ci_ai_ks_ws ', ' CodePage ')--query SQL Server encoded format statementThe following is a comparison of query results:936 Simplified Chinese GBK950 Traditional Chinese BIG5437 US/Canada English932

The use of "'" (single quotation marks): In SQL Server, two "'" (single quotation marks) in the case of stitching strings, that is, the concatenation of a "'" single quote string.SELECT TOP 1 " '"+CONVERT(nvarchar( -), keyID)+" '"Name1

SQL Server of backup and recoverySQL Server:Backup command:BackupDatabase Testto disk = ' C:\Test 'With FORMAT,NAME = ' Full Backup of MyNwind 'The explanations are as follows:NAME = ' Full Backup of MyNwind '-this is the remark, write it

--page (starting from 1) pagesize--Method 1 (not high efficiency):SELECT TOP ten * from [XXX]. [Oooo]WHEREID not in(SELECT TOP (10* (3000-1)) ID from [XXX]. [Oooo] ORDER by Createtime DESC)ORDER by Createtime DESC;Method 2 (High efficiency):SELECT

operating mode:At a large level, there are only two modes of SQL Server mirroring: High security mode and high performance mode. The main difference between the two modes is the operation after the transaction is committed. You can view the run mode

Method One: Take advantage of cursors, but be aware of the main field or identity columnDeclare @max integer,@id integerDeclareCur_rowscursorLocal for SelectMain field,Count(*) fromTable nameGroup byMain field having Count(*)> 1Opencur_rowsFetchCur_

Just say the principle, you can use the program to generate HTM or Word documents.1, first get all the tablesSELECT name, id from sysobjects WHERE xtype = ' u ' ORDER by name ASC2. Query the field information according to the table nameSelect

For production data, the security of data is critical, and any loss of data can have serious consequences. Backup as a copy of the data, can effectively protect and restore dataReasons for data lossThe main reasons for data loss include the

Back up before modifying or deleting data, back up first, back up (important things say three times)!1, first, look at the thread, analyze whether there is a blocking process, blocked>0 are currently blocked processesSELECT * from sysprocesses where

DECLARE @Str NVARCHAR( -)= '1_bb_cc_dd_aa_ee_yy_ww_hh_gg'--//1. Gets the number of times an underscore appears in a stringSELECT LEN(@Str)- LEN(REPLACE(@Str,'_',"'))--//2. Get the subscript where the underline appearsIF EXISTS(SELECT *

SQL Server is a database management system that runs primarily through windows services. This article mainly introduces how to perform basic operation and management of the database.Start or stop the database serviceAfter you complete the database

SQL Server is a database management system that runs primarily through windows services. This article mainly introduces how to perform basic operation and management of the database.Start or stop the database serviceAfter you complete the database

Although it is not recommended to use commands to delete things in a database table, these delete commands are always useful.When it comes to deleting table data, the biggest thing you can remember is the delete.However, we do database development