coalesce statement in sql

table TableNameSELECT * Into TableName from #Tmpdrop table #TmpThis duplication occurs because the table is poorly designed and the unique index columns are added to resolve.2, this kind of repetition problem usually requires to keep the first record in the duplicate record, the operation method is as followsSuppose there is a duplicate field name,address, which requires the result set to be unique for both fieldsSelect Identity (int,1,1) as Autoid, * into #Tmp from TableNameSelect min (autoid)

Hibernate native SQL query Multiple table Association, SQL statement to pay attention to the problem@for ever 2009-9-4System environment:MySQL5.1Hibernate3.3The assumption is as follows:The entity classes Question and answer correspond to the data table Question and answer respectively.and the fields of table question and answer are mostly the same, and the numbe

by setting Statistics we can view the system situation when executing SQL. The options are Profile,io, time. Introduced as follows:SET STATISTICS profile on: Displays the time, in milliseconds, that is required to parse, compile, and execute the query.SET STATISTICS IO on: reports information about the number of scans per table referenced in the statement, the number of logical reads (pages accessed in the

The first day (Datefirst) setting determines which day your system uses as the first day of the week. All of the following examples are established in Sunday as the first day of the week, with the first day set to 7. If your first day setting is not the same, you may need to adjust these examples so that it matches the different first-day settings. You can check the first day setting by using the @ @DATEFIRST function. Let's review the DateDiff and DATEADD functions first. The DateDiff functio

--View FOREIGN KEY constraints for the specified table SELECT * from sysobjects where parent_obj in ( Select id from sysobjects where name= ' table name ') and xtype= ' PK ' --View All tables SELECT * from sysobjects where xtype= ' PK ' --Delete a column containing numbers Delete News where Patindex ('%[0-9]% ', title) >0 --delete the row that duplicates the title value of the field and keep only the smaller ID Delete News where exists (select 1 from News t where T.title=news.title and T.id--Vie

: Check wooyundrops try to enter SQL statements manually using xp_cmdshell to execute commandsTest 4 Result: Unable to connect server, return 404 page; ----------------------------------------------------- ; EXEC Master. xp_cmdshell ' net user '--- Test 5 Purpose: Try to add the% symbol to the keyword, the OUTPUT keyword to determine which keyword is filtered;Test 5 Result: Xp_cmdshell,sp_configure and no filter? However, a

Label:The SQL statement in the company's code may be called by multiple methods, but some methods will be associated with other tables, so if the modification is inappropriate, the same method of invoking the SQL statement will cause an error.Recently done a function of the company, there is such a problem, although th

INTO keyword can be added without adding it to enhance the readability of the statement. Casual ~Note: Columns cannot be set to a null value if there are three cases in which the value is interpolated1. The column is defined as the default value.2. The column is defined to accept some form of system generated value. For example, the identity value3. The value of the column has been supplied when inserting the data.(The stored Procedure sp_help featur

SQL Server 2008 provides an enhanced SQL command merge for use in the msdn:http://msdn.microsoft.com/zh-cn/library/bb510625.aspx Function: Inserts, updates, or deletes on the target table based on the results of joining with the source table. For example, you can synchronize two tables by inserting, updating, or deleting rows in a table based on differences found in another table. Let's take a look at an

SQL statement to create job scheduling under SQL Server 2000 -- Define job creationDECLARE @ jobid uniqueidentifierEXEC msdb. dbo. sp_add_job@ Job_name = n' job name ',@ Job_id = @ jobid OUTPUT-- Define job stepsDECLARE @ SQL nvarchar (400), @ dbname sysnameSELECT @ dbname = DB_NAME (), -- the job step is executed in t

* from schedule where DateDiff (' minute ', F start time, GETDATE ()) >513, Description: An SQL statement that takes care of database pagingSelect Top b.* from (select Top 20 primary key field, sort field from table name order by sort field desc) A, table name B where B. primary key field = A. primary key field order by a. Sort Field 14 , Description: Top 10 recordsSelect top * form table1 where scope 15,

T-SQL statement and several database engines, t-SQL Database Engine Create a table Note: A. Self-Growth B. database engine,ISAM is a well-defined and time-tested data table management method. It is designed to take into account that the number of database queries is much larger than the number of updates. Therefore, ISAM performs read operations quickly without o

Say the question first.Results of direct SQL executionvar result = base. Context.Customers.SqlQuery (SQL);　The SQL statement is a break point, the connection is also a database, but the results are inconsistentIt is also correct to use SqlDataAdapter to fetch data into a dataset.So you can rule out a problem with the

Tags: Oracle database SQL optimization about SQL statement optimization methods Some are generic (such as avoiding select *); Some different database management systems differ (such as WHERE clause order); You then have to tune according to the actual environment, because even the same databases and tables, SQL