how to tune sql query

Label:In SQL Server, each query will find the shortest path to achieve its own goal. If the database accepts only one connection at a time, only one query is executed. Then the query is, of course, M.F.B. s to complete the work. For most databases, however, multiple queries need to be processed at the same time. Instea

Tags: index solution based on keyword har results in SQL Server failure efficiencyProblem: There's a lot of data on both tables. The A1 field in a table needs to be associated with the B table primary key query A1 field stores multiple B table primary keys The format is: Format 1:B1,B2,B3 Format 2:B4 Format 3:b5,b6 Comma-delimited minority This leads to the use of like '%...% ', charindex, or replace (A1,B1

1, display line numberIf the data is not deleted, the primary key is consistent with the row number, but when some data is deleted, the row number is inconsistent with the primary key, and the need to query the line number requires a new method, and the temporary table is required before SQL Server2005, but in SQL Server2005, using the Row_ Number () is very conv

How to compile efficient SQL query statements and SQL statementsOverview How can I write SQL query statements with high performance? Two Methods: creating reasonable indexes and writing efficient SQL statements Basic Principles of

achievement of the same students with different course grades.43. Check the top two of the best results for each door44. The number of students enrolled in each course (more than 10 participants are counted). Require the output of the course number and the number of elective, query results in descending order of numbers, query results in descending order of numbers, if the number is the same, in ascending

SQL statement Optimization-query different rows of the two tables NOT IN, NOT EXISTS, Join query Left Join, existsleft In actual development, we often need to compare the differences between two or more tables and compare the data that is the same and the data is different. At this time, we can use the following three methods: 1. IN or not in, 2. EXIST or NOTEXIS

Label:Today, I ran into a problem with a Sybase database query. A simple SQL, but do not know why the query does not come out, resulting in the production of the production server frequently hang out. Scared my little heart to bang. Select as Fcilcde from dnd_event_log A WHERE a.doc_ref =? and A.doc_type =? ' S ' Later, the network Operations Manager, the

Tags: static void Main (string[] args) {string table name = "Water_emstime"; String sql = "Exec gettableselect" + table name; String constring = "Server=xxx.xxx.xx.xx;database=newfw;uid=sa;pwd=sa"; SqlDataAdapter da = new SqlDataAdapter (SQL, constring); DataSet ds = new DataSet (); Da. Fill (DS); String parmslist = ""; foreach (Dat

Introduction to the Decode () function:Main role: Translation of query results into other values (that is, in other forms of expression, the following examples);How to use:Select decode (ColumnName, value 1, translation value 1, value 2, translation value 2,... Value n, translation value n, default value)From TalbenameWhere ...Where ColumnName is the column defined in the table to be selected,• Explanation of Meaning:Decode (condition, value 1, transl

Original: SQL Server 2012:SQL Server architecture--The life cycle of a query (part 2nd)Planning cache (Plan caches)If SQL Server has found a good way to execute a piece of code, it should be reused as a subsequent request because Generating execution plans is time-consuming and resource-intensive, There is a point in d

IntroductionSee a popular blog today. NET Senior Engineer face questions of SQL, asked to find the highest score of each department, and by the department number, the student number in ascending order. This query is more complex, but also more typical, since the use of ORM, a long time did not write SQL statements, so I studied the next, I also wrote a: With Cte1

Method 1:When the publisher filter condition is NULL, how do you write SQL?1 DECLARE @publishers VARCHAR (50);2 SELECT * FROM dbo. Book WHERE Publishers=isnull (@publishers, publishers)Method 2:DECLARE @cinv varchar (50)SELECT * from inventory where 1=1 and ([email protected] or @cinv is null)Method 3:DECLARE @name VARCHAR (+), @page INT =1SET @name = ' Zhang San 'DECLARE @sql VARCHAR (1000)SET @

Enable AD Hoc distributed Queries: ' Show advanced Options ', 1 Reconfigure ' Ad Hoc distributed Queries ', 1 Reconfigure When you are finished using, close ad Hoc distributed Queries:' Ad Hoc distributed Queries ', 0 Reconfigure ' Show advanced Options ', 0 Reconfigure Operation: ' SQLOLEDB ' ' SQL Server name ' ' User name ' ' Password ' ' SQLOLEDB ' ' SQL Server name ' ' User name ' ' Passw

Tags: tis sel using-o col Hal Link query imgALWAYSON has occurred 2 times, logged: DBCC execution is complete. If DBCC outputs an error message, contact your system administrator. Msg 2767, Level 16, State 1, procedure Sp_table_statistics2_rowset, line 105thStatistics ' _wa_sys_0000001c_090a5324 ' cannot be found in the system directory.DBCC execution is complete. If DBCC outputs an error message, contact your system administrator.