query tuning in sql server

A few days ago, I found that the query on the website is abnormal. Generally, the content of the first-level directory is queried first, and the second-level directory is queried after I click the first-level directory ...... Until the bottom file is found. However, these days, we found that the query speed was very slow, and the query results were not a level-1

Label:Use a normal socket to simulate a connection to MySQL server and send a query SQL, as shown in the following code: Socketsocket=newsocket ("127.0.0.1", 3306); Outputstreamout=socket.getoutputstream (); Bufferedoutputstreambos=newbufferedoutputstream (out); Establish connection message information from Wireshark (login when capturing terminal execution mysq

SQL Server dynamic query (table name or field dynamic), and get the desired return value result (Exec sp_execute Key words: In the preparation of SQL statements or stored procedures, it is inevitable that the table name or a field name in the statement is not sure. In this case, we should co

Select. *, B. * From OpenRowSet ('msdasql ', 'driver = {SQL Server}; server = 119.254.245; uid = sa; Pwd = abc123_kxr', mall_master.dbo.product) as a, kxr_products B -- where, tom is the remote server name, and stores is the table in the local database pubs. Note that if the number of records in the two tables is diffe

I once met a user who has a very large MSDB database and asked me to help find out why. Use sp_spaceused to find the data size of all tables. The problem is that SQL Server backs up and restores the historical table to a large amount of data. You often back up logs, but never clear historical records. Later, when the maintenance plan was set up to regularly clear the backup records, the problem would not oc

Use ISNULL in SQL Server to execute null value judgment query, serverisnull The following queries are available:Copy codeThe Code is as follows:Select isnull (lastchanged, '') as lastchanged from vhhostlist where s_comment = 'test202'Originally, the ISNULL function has only one parameter. It indicates that the parameter is used to determine whether the value of t

BackgroundWhen using Oracle or other databases, using the LIKE keyword for fuzzy query is commonly used by people, in the use of pure Chinese environment is very easy to use, there are some wildcards can be used, but in a pure English environment, the size of the need to accurately match the problem, the main reason is the problem of string FL like '%{0}% ' and Here like after is a string, so there must be a size-sensitive problem. For e

Tags: and SQL difference create type must automatically update drop bookDifferences between queries in Access and view in SQL ServerAlthough both can be used to create a drop view Delete in Delphi, but the two are not the sameSuppose there are table book and booktype associated Build query (view) V_bookWhen you add a new field to the Book table, V_book in Access

Original: SQL Server 2008 Technical Insider--t-sql query notes1, SQL Programming has many unique features, such as: set-oriented thinking mode, query elements of the logical processing sequence, three-valued logic. If you do not h

When the database is troubleshooting according to regulations, you need to view each of the 50 tables in the database to ensure that all fields that are expected to be the default value are assigned the default value. It can be imagined that this is a daunting task. Is there a better way to view this schema than opening every table in the SQL server administration suite?By querying three system tables in an

we use a undocument query prompt directly to the statement, forcing the parallel cost threshold for the query to be dropped to 0, forcing the statement to go in parallel, and the statement execution time from 20 seconds to 5 seconds (note: Use a hash join hint for 7 seconds). The following is a simple example showing the effect of using this hint, example T-SQL

is NULL, then 0 is returned.Then the query ID value is greater than the record of the maximum ID value for the first 40 records.This query has one condition, that is, the ID must be of type int.The third method:Select Top 10 *From(Select Row_number () over (order by ID) as rownumber,* from test) Awhere RowNumber > 40Principle: First sort all the data in the table according to a rownumber, then

on the statement, which causes the parallel cost threshold of the query to be reduced to 0, which forces the statement to go parallel and the statement execution time from 20 seconds to 5 seconds (note: Using the hash join hint is 7 seconds). The following is a simple example of the effect of using this hint, as shown in Listing 1 of the sample T-sql: SELECT *FromINNER JOIN [Sales]. SalesOrderHeader b on A

Tags: Comm syntax sugar Session server efficiency allows nbsp Eve mysq--sql Server allows dirty read query sqlSELECT * from category with (NOLOCK)--mysql allow dirty read query SQL MYSQL No syntax sugar, requires native SQLSET SES

Getting Started with SQL XML:--by jinjazz 1. xml: Ability to recognize elements, attributes, and values 2. XPath: addressing language, lookup similar to Windows directory (go to the wall if you don't use the dir command) Syntax format, which can be combined as a condition: "." Express oneself, "..." Said the father, "/" said the Son, "//" to indicate the offspring, "Name" means find by First name, "@name" means find by property Set [condition] represe